* Check in Fred Fish's changes in these modules. Fred

[binutils-gdb.git] / gdb / dwarfread.c

/* DWARF debugging format support for GDB.
   Copyright (C) 1991, 1992 Free Software Foundation, Inc.
   Written by Fred Fish at Cygnus Support.  Portions based on dbxread.c,
   mipsread.c, coffread.c, and dwarfread.c from a Data General SVR4 gdb port.

This file is part of GDB.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*

FIXME: Figure out how to get the frame pointer register number in the
execution environment of the target.  Remove R_FP kludge

FIXME: Add generation of dependencies list to partial symtab code.

FIXME: Currently we ignore host/target byte ordering and integer size
differences.  Should remap data from external form to an internal form
before trying to use it.

FIXME: Resolve minor differences between what information we put in the
partial symbol table and what dbxread puts in.  For example, we don't yet
put enum constants there.  And dbxread seems to invent a lot of typedefs
we never see.  Use the new printpsym command to see the partial symbol table
contents.

FIXME: Figure out a better way to tell gdb about the name of the function
contain the user's entry point (I.E. main())

FIXME: The current DWARF specification has a very strong bias towards
machines with 32-bit integers, as it assumes that many attributes of the
program (such as an address) will fit in such an integer.  There are many
references in the spec to things that are 2, 4, or 8 bytes long.  Given that
we will probably run into problems on machines where some of these assumptions
are invalid (64-bit ints for example), we don't bother at this time to try to
make this code more flexible and just use shorts, ints, and longs (and their
sizes) where it seems appropriate.  I.E. we use a short int to hold DWARF
tags, and assume that the tag size in the file is the same as sizeof(short).

FIXME: See other FIXME's and "ifdef 0" scattered throughout the code for
other things to work on, if you get bored. :-)

*/

#include <stdio.h>
#include <varargs.h>
#include <fcntl.h>

#include "defs.h"
#include "bfd.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "symfile.h"
#include "elf/dwarf.h"
#include "buildsym.h"

#ifdef MAINTENANCE      /* Define to 1 to compile in some maintenance stuff */
#define SQUAWK(stuff) dwarfwarn stuff
#else
#define SQUAWK(stuff)
#endif

#ifndef R_FP            /* FIXME */
#define R_FP 14         /* Kludge to get frame pointer register number */
#endif

typedef unsigned int DIEREF;    /* Reference to a DIE */

#ifndef GCC_PRODUCER
#define GCC_PRODUCER "GNU C "
#endif

#define STREQ(a,b)              (strcmp(a,b)==0)
#define STREQN(a,b,n)           (strncmp(a,b,n)==0)

/* The Amiga SVR4 header file <dwarf.h> defines AT_element_list as a
   FORM_BLOCK2, and this is the value emitted by the AT&T compiler.
   However, the Issue 2 DWARF specification from AT&T defines it as
   a FORM_BLOCK4, as does the latest specification from UI/PLSIG.
   For backwards compatibility with the AT&T compiler produced executables
   we define AT_short_element_list for this variant. */

#define AT_short_element_list    (0x00f0|FORM_BLOCK2)

/* External variables referenced. */

extern CORE_ADDR startup_file_start;    /* From blockframe.c */
extern CORE_ADDR startup_file_end;      /* From blockframe.c */
extern CORE_ADDR entry_scope_lowpc;     /* From blockframe.c */
extern CORE_ADDR entry_scope_highpc;    /* From blockframc.c */
extern CORE_ADDR main_scope_lowpc;      /* From blockframe.c */
extern CORE_ADDR main_scope_highpc;     /* From blockframc.c */
extern int info_verbose;                /* From main.c; nonzero => verbose */


/* The DWARF debugging information consists of two major pieces,
   one is a block of DWARF Information Entries (DIE's) and the other
   is a line number table.  The "struct dieinfo" structure contains
   the information for a single DIE, the one currently being processed.

   In order to make it easier to randomly access the attribute fields
   of the current DIE, which are specifically unordered within the DIE
   each DIE is scanned and an instance of the "struct dieinfo"
   structure is initialized.

   Initialization is done in two levels.  The first, done by basicdieinfo(),
   just initializes those fields that are vital to deciding whether or not
   to use this DIE, how to skip past it, etc.  The second, done by the
   function completedieinfo(), fills in the rest of the information.

   Attributes which have block forms are not interpreted at the time
   the DIE is scanned, instead we just save pointers to the start
   of their value fields.

   Some fields have a flag <name>_p that is set when the value of the
   field is valid (I.E. we found a matching attribute in the DIE).  Since
   we may want to test for the presence of some attributes in the DIE,
   such as AT_low_pc, without restricting the values of the field,
   we need someway to note that we found such an attribute.
   
 */
   
typedef char BLOCK;

struct dieinfo {
  char *        die;                    /* Pointer to the raw DIE data */
  long          dielength;              /* Length of the raw DIE data */
  DIEREF        dieref;                 /* Offset of this DIE */
  short         dietag;                 /* Tag for this DIE */
  long          at_padding;
  long          at_sibling;
  BLOCK *       at_location;
  char *        at_name;
  unsigned short at_fund_type;
  BLOCK *       at_mod_fund_type;
  long          at_user_def_type;
  BLOCK *       at_mod_u_d_type;
  short         at_ordering;
  BLOCK *       at_subscr_data;
  long          at_byte_size;
  short         at_bit_offset;
  long          at_bit_size;
  BLOCK *       at_element_list;
  long          at_stmt_list;
  long          at_low_pc;
  long          at_high_pc;
  long          at_language;
  long          at_member;
  long          at_discr;
  BLOCK *       at_discr_value;
  short         at_visibility;
  long          at_import;
  BLOCK *       at_string_length;
  char *        at_comp_dir;
  char *        at_producer;
  long          at_frame_base;
  long          at_start_scope;
  long          at_stride_size;
  long          at_src_info;
  short         at_prototyped;
  unsigned int  has_at_low_pc:1;
  unsigned int  has_at_stmt_list:1;
  unsigned int  short_element_list:1;
};

static int diecount;    /* Approximate count of dies for compilation unit */
static struct dieinfo *curdie;  /* For warnings and such */

static char *dbbase;    /* Base pointer to dwarf info */
static int dbroff;      /* Relative offset from start of .debug section */
static char *lnbase;    /* Base pointer to line section */
static int isreg;       /* Kludge to identify register variables */
static int offreg;      /* Kludge to identify basereg references */

static CORE_ADDR baseaddr;      /* Add to each symbol value */

/* Each partial symbol table entry contains a pointer to private data for the
   read_symtab() function to use when expanding a partial symbol table entry
   to a full symbol table entry.  For DWARF debugging info, this data is
   contained in the following structure and macros are provided for easy
   access to the members given a pointer to a partial symbol table entry.

   dbfoff       Always the absolute file offset to the start of the ".debug"
                section for the file containing the DIE's being accessed.

   dbroff       Relative offset from the start of the ".debug" access to the
                first DIE to be accessed.  When building the partial symbol
                table, this value will be zero since we are accessing the
                entire ".debug" section.  When expanding a partial symbol
                table entry, this value will be the offset to the first
                DIE for the compilation unit containing the symbol that
                triggers the expansion.

   dblength     The size of the chunk of DIE's being examined, in bytes.

   lnfoff       The absolute file offset to the line table fragment.  Ignored
                when building partial symbol tables, but used when expanding
                them, and contains the absolute file offset to the fragment
                of the ".line" section containing the line numbers for the
                current compilation unit.
 */

struct dwfinfo {
  int dbfoff;           /* Absolute file offset to start of .debug section */
  int dbroff;           /* Relative offset from start of .debug section */
  int dblength;         /* Size of the chunk of DIE's being examined */
  int lnfoff;           /* Absolute file offset to line table fragment */
};

#define DBFOFF(p) (((struct dwfinfo *)((p)->read_symtab_private))->dbfoff)
#define DBROFF(p) (((struct dwfinfo *)((p)->read_symtab_private))->dbroff)
#define DBLENGTH(p) (((struct dwfinfo *)((p)->read_symtab_private))->dblength)
#define LNFOFF(p) (((struct dwfinfo *)((p)->read_symtab_private))->lnfoff)

/* The generic symbol table building routines have separate lists for
   file scope symbols and all all other scopes (local scopes).  So
   we need to select the right one to pass to add_symbol_to_list().
   We do it by keeping a pointer to the correct list in list_in_scope.

   FIXME:  The original dwarf code just treated the file scope as the first
   local scope, and all other local scopes as nested local scopes, and worked
   fine.  Check to see if we really need to distinguish these in buildsym.c */

struct pending **list_in_scope = &file_symbols;

/* DIES which have user defined types or modified user defined types refer to
   other DIES for the type information.  Thus we need to associate the offset
   of a DIE for a user defined type with a pointer to the type information.

   Originally this was done using a simple but expensive algorithm, with an
   array of unsorted structures, each containing an offset/type-pointer pair.
   This array was scanned linearly each time a lookup was done.  The result
   was that gdb was spending over half it's startup time munging through this
   array of pointers looking for a structure that had the right offset member.

   The second attempt used the same array of structures, but the array was
   sorted using qsort each time a new offset/type was recorded, and a binary
   search was used to find the type pointer for a given DIE offset.  This was
   even slower, due to the overhead of sorting the array each time a new
   offset/type pair was entered.

   The third attempt uses a fixed size array of type pointers, indexed by a
   value derived from the DIE offset.  Since the minimum DIE size is 4 bytes,
   we can divide any DIE offset by 4 to obtain a unique index into this fixed
   size array.  Since each element is a 4 byte pointer, it takes exactly as
   much memory to hold this array as to hold the DWARF info for a given
   compilation unit.  But it gets freed as soon as we are done with it. */

static struct type **utypes;    /* Pointer to array of user type pointers */
static int numutypes;           /* Max number of user type pointers */

/* Forward declarations of static functions so we don't have to worry
   about ordering within this file.  */

static void
add_enum_psymbol PARAMS ((struct dieinfo *, struct objfile *));

static void
read_file_scope PARAMS ((struct dieinfo *, char *, char *, struct objfile *));

static void
read_func_scope PARAMS ((struct dieinfo *, char *, char *, struct objfile *));

static void
read_lexical_block_scope PARAMS ((struct dieinfo *, char *, char *,
                                  struct objfile *));

static void
dwarfwarn ();

static void
scan_partial_symbols PARAMS ((char *, char *, struct objfile *));

static void
scan_compilation_units PARAMS ((char *, char *, char *, unsigned int,
                                unsigned int, struct objfile *));

static void
add_partial_symbol PARAMS ((struct dieinfo *, struct objfile *));

static void
init_psymbol_list PARAMS ((struct objfile *, int));

static void
basicdieinfo PARAMS ((struct dieinfo *, char *));

static void
completedieinfo PARAMS ((struct dieinfo *));

static void
dwarf_psymtab_to_symtab PARAMS ((struct partial_symtab *));

static void
psymtab_to_symtab_1 PARAMS ((struct partial_symtab *));

static struct symtab *
read_ofile_symtab PARAMS ((struct partial_symtab *));

static void
process_dies PARAMS ((char *, char *, struct objfile *));

static void
read_structure_scope PARAMS ((struct dieinfo *, char *, char *,
                              struct objfile *));

static struct type *
decode_array_element_type PARAMS ((char *, char *));

static struct type *
decode_subscr_data PARAMS ((char *, char *));

static void
dwarf_read_array_type PARAMS ((struct dieinfo *));

static void
read_tag_pointer_type PARAMS ((struct dieinfo *dip));

static void
read_subroutine_type PARAMS ((struct dieinfo *, char *, char *));

static void
read_enumeration PARAMS ((struct dieinfo *, char *, char *, struct objfile *));

static struct type *
struct_type PARAMS ((struct dieinfo *, char *, char *, struct objfile *));

static struct type *
enum_type PARAMS ((struct dieinfo *, struct objfile *));

static void
decode_line_numbers PARAMS ((char *));

static struct type *
decode_die_type PARAMS ((struct dieinfo *));

static struct type *
decode_mod_fund_type PARAMS ((char *));

static struct type *
decode_mod_u_d_type PARAMS ((char *));

static struct type *
decode_modified_type PARAMS ((unsigned char *, unsigned int, int));

static struct type *
decode_fund_type PARAMS ((unsigned int));

static char *
create_name PARAMS ((char *, struct obstack *));

static struct type *
lookup_utype PARAMS ((DIEREF));

static struct type *
alloc_utype PARAMS ((DIEREF, struct type *));

static struct symbol *
new_symbol PARAMS ((struct dieinfo *, struct objfile *));

static int
locval PARAMS ((char *));

static void
record_minimal_symbol PARAMS ((char *, CORE_ADDR, enum minimal_symbol_type,
                               struct objfile *));

/*

GLOBAL FUNCTION

        dwarf_build_psymtabs -- build partial symtabs from DWARF debug info

SYNOPSIS

        void dwarf_build_psymtabs (int desc, char *filename, CORE_ADDR addr,
             int mainline, unsigned int dbfoff, unsigned int dbsize,
             unsigned int lnoffset, unsigned int lnsize,
             struct objfile *objfile)

DESCRIPTION

        This function is called upon to build partial symtabs from files
        containing DIE's (Dwarf Information Entries) and DWARF line numbers.

        It is passed a file descriptor for an open file containing the DIES
        and line number information, the corresponding filename for that
        file, a base address for relocating the symbols, a flag indicating
        whether or not this debugging information is from a "main symbol
        table" rather than a shared library or dynamically linked file,
        and file offset/size pairs for the DIE information and line number
        information.

RETURNS

        No return value.

 */

void
dwarf_build_psymtabs (desc, filename, addr, mainline, dbfoff, dbsize,
                      lnoffset, lnsize, objfile)
     int desc;
     char *filename;
     CORE_ADDR addr;
     int mainline;
     unsigned int dbfoff;
     unsigned int dbsize;
     unsigned int lnoffset;
     unsigned int lnsize;
     struct objfile *objfile;
{
  struct cleanup *back_to;
  
  dbbase = xmalloc (dbsize);
  dbroff = 0;
  if ((lseek (desc, dbfoff, 0) != dbfoff) ||
      (read (desc, dbbase, dbsize) != dbsize))
    {
      free (dbbase);
      error ("can't read DWARF data from '%s'", filename);
    }
  back_to = make_cleanup (free, dbbase);
  
  /* If we are reinitializing, or if we have never loaded syms yet, init.
     Since we have no idea how many DIES we are looking at, we just guess
     some arbitrary value. */
  
  if (mainline || objfile->global_psymbols.size == 0 || objfile->static_psymbols.size == 0)
    {
      init_psymbol_list (objfile, 1024);
    }
  
  /* From this point on, we don't need to pass mainline around, so zap
     baseaddr to zero if we don't need relocation. */

  if (mainline)
    {
      baseaddr = 0;
    }
  else
    {
      baseaddr = addr;
    }

  /* Follow the compilation unit sibling chain, building a partial symbol
     table entry for each one.  Save enough information about each compilation
     unit to locate the full DWARF information later. */
  
  scan_compilation_units (filename, dbbase, dbbase + dbsize,
                          dbfoff, lnoffset, objfile);
  
  do_cleanups (back_to);
}


/*

LOCAL FUNCTION

        record_minimal_symbol -- add entry to gdb's minimal symbol table

SYNOPSIS

        static void record_minimal_symbol (char *name, CORE_ADDR address,
                                          enum minimal_symbol_type ms_type,
                                          struct objfile *objfile)

DESCRIPTION

        Given a pointer to the name of a symbol that should be added to the
        minimal symbol table, and the address associated with that
        symbol, records this information for later use in building the
        minimal symbol table.

 */

static void
record_minimal_symbol (name, address, ms_type, objfile)
     char *name;
     CORE_ADDR address;
     enum minimal_symbol_type ms_type;
     struct objfile *objfile;
{
  name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
  prim_record_minimal_symbol (name, address, ms_type);
}

/*

LOCAL FUNCTION

        dwarfwarn -- issue a DWARF related warning

DESCRIPTION

        Issue warnings about DWARF related things that aren't serious enough
        to warrant aborting with an error, but should not be ignored either.
        This includes things like detectable corruption in DIE's, missing
        DIE's, unimplemented features, etc.

        In general, running across tags or attributes that we don't recognize
        is not considered to be a problem and we should not issue warnings
        about such.

NOTES

        We mostly follow the example of the error() routine, but without
        returning to command level.  It is arguable about whether warnings
        should be issued at all, and if so, where they should go (stdout or
        stderr).

        We assume that curdie is valid and contains at least the basic
        information for the DIE where the problem was noticed.
*/

static void
dwarfwarn (va_alist)
     va_dcl
{
  va_list ap;
  char *fmt;
  
  va_start (ap);
  fmt = va_arg (ap, char *);
  warning_setup ();
  fprintf (stderr, "DWARF warning (ref 0x%x): ", curdie -> dieref);
  if (curdie -> at_name)
    {
      fprintf (stderr, "'%s': ", curdie -> at_name);
    }
  vfprintf (stderr, fmt, ap);
  fprintf (stderr, "\n");
  fflush (stderr);
  va_end (ap);
}

/*

LOCAL FUNCTION

        read_lexical_block_scope -- process all dies in a lexical block

SYNOPSIS

        static void read_lexical_block_scope (struct dieinfo *dip,
                char *thisdie, char *enddie)

DESCRIPTION

        Process all the DIES contained within a lexical block scope.
        Start a new scope, process the dies, and then close the scope.

 */

static void
read_lexical_block_scope (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  register struct context_stack *new;

  (void) push_context (0, dip -> at_low_pc);
  process_dies (thisdie + dip -> dielength, enddie, objfile);
  new = pop_context ();
  if (local_symbols != NULL)
    {
      finish_block (0, &local_symbols, new -> old_blocks, new -> start_addr,
                    dip -> at_high_pc, objfile);
    }
  local_symbols = new -> locals;
}

/*

LOCAL FUNCTION

        lookup_utype -- look up a user defined type from die reference

SYNOPSIS

        static type *lookup_utype (DIEREF dieref)

DESCRIPTION

        Given a DIE reference, lookup the user defined type associated with
        that DIE, if it has been registered already.  If not registered, then
        return NULL.  Alloc_utype() can be called to register an empty
        type for this reference, which will be filled in later when the
        actual referenced DIE is processed.
 */

static struct type *
lookup_utype (dieref)
     DIEREF dieref;
{
  struct type *type = NULL;
  int utypeidx;
  
  utypeidx = (dieref - dbroff) / 4;
  if ((utypeidx < 0) || (utypeidx >= numutypes))
    {
      dwarfwarn ("reference to DIE (0x%x) outside compilation unit", dieref);
    }
  else
    {
      type = *(utypes + utypeidx);
    }
  return (type);
}


/*

LOCAL FUNCTION

        alloc_utype  -- add a user defined type for die reference

SYNOPSIS

        static type *alloc_utype (DIEREF dieref, struct type *utypep)

DESCRIPTION

        Given a die reference DIEREF, and a possible pointer to a user
        defined type UTYPEP, register that this reference has a user
        defined type and either use the specified type in UTYPEP or
        make a new empty type that will be filled in later.

        We should only be called after calling lookup_utype() to verify that
        there is not currently a type registered for DIEREF.
 */

static struct type *
alloc_utype (dieref, utypep)
     DIEREF dieref;
     struct type *utypep;
{
  struct type **typep;
  int utypeidx;
  
  utypeidx = (dieref - dbroff) / 4;
  typep = utypes + utypeidx;
  if ((utypeidx < 0) || (utypeidx >= numutypes))
    {
      utypep = lookup_fundamental_type (current_objfile, FT_INTEGER);
      dwarfwarn ("reference to DIE (0x%x) outside compilation unit", dieref);
    }
  else if (*typep != NULL)
    {
      utypep = *typep;
      SQUAWK (("internal error: dup user type allocation"));
    }
  else
    {
      if (utypep == NULL)
        {
          utypep = (struct type *)
            obstack_alloc (&current_objfile -> type_obstack,
                           sizeof (struct type));
          (void) memset (utypep, 0, sizeof (struct type));
          TYPE_OBJFILE (utypep) = current_objfile;
        }
      *typep = utypep;
    }
  return (utypep);
}

/*

LOCAL FUNCTION

        decode_die_type -- return a type for a specified die

SYNOPSIS

        static struct type *decode_die_type (struct dieinfo *dip)

DESCRIPTION

        Given a pointer to a die information structure DIP, decode the
        type of the die and return a pointer to the decoded type.  All
        dies without specific types default to type int.
 */

static struct type *
decode_die_type (dip)
     struct dieinfo *dip;
{
  struct type *type = NULL;
  
  if (dip -> at_fund_type != 0)
    {
      type = decode_fund_type (dip -> at_fund_type);
    }
  else if (dip -> at_mod_fund_type != NULL)
    {
      type = decode_mod_fund_type (dip -> at_mod_fund_type);
    }
  else if (dip -> at_user_def_type)
    {
      if ((type = lookup_utype (dip -> at_user_def_type)) == NULL)
        {
          type = alloc_utype (dip -> at_user_def_type, NULL);
        }
    }
  else if (dip -> at_mod_u_d_type)
    {
      type = decode_mod_u_d_type (dip -> at_mod_u_d_type);
    }
  else
    {
      type = lookup_fundamental_type (current_objfile, FT_INTEGER);
    }
  return (type);
}

/*

LOCAL FUNCTION

        struct_type -- compute and return the type for a struct or union

SYNOPSIS

        static struct type *struct_type (struct dieinfo *dip, char *thisdie,
            char *enddie, struct objfile *objfile)

DESCRIPTION

        Given pointer to a die information structure for a die which
        defines a union or structure (and MUST define one or the other),
        and pointers to the raw die data that define the range of dies which
        define the members, compute and return the user defined type for the
        structure or union.
 */

static struct type *
struct_type (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  struct type *type;
  struct nextfield {
    struct nextfield *next;
    struct field field;
  };
  struct nextfield *list = NULL;
  struct nextfield *new;
  int nfields = 0;
  int n;
  char *tpart1;
  struct dieinfo mbr;
  char *nextdie;
  
  if ((type = lookup_utype (dip -> dieref)) == NULL)
    {
      /* No forward references created an empty type, so install one now */
      type = alloc_utype (dip -> dieref, NULL);
    }
  INIT_CPLUS_SPECIFIC(type);
  switch (dip -> dietag)
    {
      case TAG_structure_type:
        TYPE_CODE (type) = TYPE_CODE_STRUCT;
        tpart1 = "struct";
        break;
      case TAG_union_type:
        TYPE_CODE (type) = TYPE_CODE_UNION;
        tpart1 = "union";
        break;
      default:
        /* Should never happen */
        TYPE_CODE (type) = TYPE_CODE_UNDEF;
        tpart1 = "???";
        SQUAWK (("missing structure or union tag"));
        break;
    }
  /* Some compilers try to be helpful by inventing "fake" names for
     anonymous enums, structures, and unions, like "~0fake" or ".0fake".
     Thanks, but no thanks... */
  if (dip -> at_name != NULL
      && *dip -> at_name != '~'
      && *dip -> at_name != '.')
    {
      TYPE_NAME (type) = obconcat (&current_objfile -> type_obstack,
                                   tpart1, " ", dip -> at_name);
    }
  if (dip -> at_byte_size != 0)
    {
      TYPE_LENGTH (type) = dip -> at_byte_size;
    }
  thisdie += dip -> dielength;
  while (thisdie < enddie)
    {
      basicdieinfo (&mbr, thisdie);
      completedieinfo (&mbr);
      if (mbr.dielength <= sizeof (long))
        {
          break;
        }
      else if (mbr.at_sibling != 0)
        {
          nextdie = dbbase + mbr.at_sibling - dbroff;
        }
      else
        {
          nextdie = thisdie + mbr.dielength;
        }
      switch (mbr.dietag)
        {
        case TAG_member:
          /* Get space to record the next field's data.  */
          new = (struct nextfield *) alloca (sizeof (struct nextfield));
          new -> next = list;
          list = new;
          /* Save the data.  */
          list -> field.name = savestring (mbr.at_name, strlen (mbr.at_name));
          list -> field.type = decode_die_type (&mbr);
          list -> field.bitpos = 8 * locval (mbr.at_location);
          list -> field.bitsize = 0;
          nfields++;
          break;
        default:
          process_dies (thisdie, nextdie, objfile);
          break;
        }
      thisdie = nextdie;
    }
  /* Now create the vector of fields, and record how big it is.  We may
     not even have any fields, if this DIE was generated due to a reference
     to an anonymous structure or union.  In this case, TYPE_FLAG_STUB is
     set, which clues gdb in to the fact that it needs to search elsewhere
     for the full structure definition. */
  if (nfields == 0)
    {
      TYPE_FLAGS (type) |= TYPE_FLAG_STUB;
    }
  else
    {
      TYPE_NFIELDS (type) = nfields;
      TYPE_FIELDS (type) = (struct field *)
        obstack_alloc (&current_objfile -> type_obstack,
                       sizeof (struct field) * nfields);
      /* Copy the saved-up fields into the field vector.  */
      for (n = nfields; list; list = list -> next)
        {
          TYPE_FIELD (type, --n) = list -> field;
        }       
    }
  return (type);
}

/*

LOCAL FUNCTION

        read_structure_scope -- process all dies within struct or union

SYNOPSIS

        static void read_structure_scope (struct dieinfo *dip,
                char *thisdie, char *enddie, struct objfile *objfile)

DESCRIPTION

        Called when we find the DIE that starts a structure or union
        scope (definition) to process all dies that define the members
        of the structure or union.  DIP is a pointer to the die info
        struct for the DIE that names the structure or union.

NOTES

        Note that we need to call struct_type regardless of whether or not
        the DIE has an at_name attribute, since it might be an anonymous
        structure or union.  This gets the type entered into our set of
        user defined types.

        However, if the structure is incomplete (an opaque struct/union)
        then suppress creating a symbol table entry for it since gdb only
        wants to find the one with the complete definition.  Note that if
        it is complete, we just call new_symbol, which does it's own
        checking about whether the struct/union is anonymous or not (and
        suppresses creating a symbol table entry itself).
        
 */

static void
read_structure_scope (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  struct type *type;
  struct symbol *sym;
  
  type = struct_type (dip, thisdie, enddie, objfile);
  if (!(TYPE_FLAGS (type) & TYPE_FLAG_STUB))
    {
      if ((sym = new_symbol (dip, objfile)) != NULL)
        {
          SYMBOL_TYPE (sym) = type;
        }
    }
}

/*

LOCAL FUNCTION

        decode_array_element_type -- decode type of the array elements

SYNOPSIS

        static struct type *decode_array_element_type (char *scan, char *end)

DESCRIPTION

        As the last step in decoding the array subscript information for an
        array DIE, we need to decode the type of the array elements.  We are
        passed a pointer to this last part of the subscript information and
        must return the appropriate type.  If the type attribute is not
        recognized, just warn about the problem and return type int.
 */

static struct type *
decode_array_element_type (scan, end)
     char *scan;
     char *end;
{
  struct type *typep;
  short attribute;
  DIEREF dieref;
  unsigned short fundtype;
  
  (void) memcpy (&attribute, scan, sizeof (short));
  scan += sizeof (short);
  switch (attribute)
    {
    case AT_fund_type:
      (void) memcpy (&fundtype, scan, sizeof (short));
      typep = decode_fund_type (fundtype);
      break;
    case AT_mod_fund_type:
      typep = decode_mod_fund_type (scan);
      break;
    case AT_user_def_type:
      (void) memcpy (&dieref, scan, sizeof (DIEREF));
      if ((typep = lookup_utype (dieref)) == NULL)
        {
          typep = alloc_utype (dieref, NULL);
        }
      break;
    case AT_mod_u_d_type:
      typep = decode_mod_u_d_type (scan);
      break;
    default:
      SQUAWK (("bad array element type attribute 0x%x", attribute));
      typep = lookup_fundamental_type (current_objfile, FT_INTEGER);
      break;
    }
  return (typep);
}

/*

LOCAL FUNCTION

        decode_subscr_data -- decode array subscript and element type data

SYNOPSIS

        static struct type *decode_subscr_data (char *scan, char *end)

DESCRIPTION

        The array subscripts and the data type of the elements of an
        array are described by a list of data items, stored as a block
        of contiguous bytes.  There is a data item describing each array
        dimension, and a final data item describing the element type.
        The data items are ordered the same as their appearance in the
        source (I.E. leftmost dimension first, next to leftmost second,
        etc).

        We are passed a pointer to the start of the block of bytes
        containing the data items, and a pointer to the first byte past
        the data.  This function decodes the data and returns a type.

BUGS
        FIXME:  This code only implements the forms currently used
        by the AT&T and GNU C compilers.

        The end pointer is supplied for error checking, maybe we should
        use it for that...
 */

static struct type *
decode_subscr_data (scan, end)
     char *scan;
     char *end;
{
  struct type *typep = NULL;
  struct type *nexttype;
  int format;
  short fundtype;
  long lowbound;
  long highbound;
  
  format = *scan++;
  switch (format)
    {
    case FMT_ET:
      typep = decode_array_element_type (scan, end);
      break;
    case FMT_FT_C_C:
      (void) memcpy (&fundtype, scan, sizeof (short));
      scan += sizeof (short);
      if (fundtype != FT_integer && fundtype != FT_signed_integer
          && fundtype != FT_unsigned_integer)
        {
          SQUAWK (("array subscripts must be integral types, not type 0x%x",
                     fundtype));
        }
      else
        {
          (void) memcpy (&lowbound, scan, sizeof (long));
          scan += sizeof (long);
          (void) memcpy (&highbound, scan, sizeof (long));
          scan += sizeof (long);
          nexttype = decode_subscr_data (scan, end);
          if (nexttype != NULL)
            {
              typep = (struct type *)
                obstack_alloc (&current_objfile -> type_obstack,
                               sizeof (struct type));
              (void) memset (typep, 0, sizeof (struct type));
              TYPE_OBJFILE (typep) = current_objfile;
              TYPE_CODE (typep) = TYPE_CODE_ARRAY;
              TYPE_LENGTH (typep) = TYPE_LENGTH (nexttype);
              TYPE_LENGTH (typep) *= lowbound + highbound + 1;
              TYPE_TARGET_TYPE (typep) = nexttype;
            }               
        }
      break;
    case FMT_FT_C_X:
    case FMT_FT_X_C:
    case FMT_FT_X_X:
    case FMT_UT_C_C:
    case FMT_UT_C_X:
    case FMT_UT_X_C:
    case FMT_UT_X_X:
      SQUAWK (("array subscript format 0x%x not handled yet", format));
      break;
    default:
      SQUAWK (("unknown array subscript format %x", format));
      break;
    }
  return (typep);
}

/*

LOCAL FUNCTION

        dwarf_read_array_type -- read TAG_array_type DIE

SYNOPSIS

        static void dwarf_read_array_type (struct dieinfo *dip)

DESCRIPTION

        Extract all information from a TAG_array_type DIE and add to
        the user defined type vector.
 */

static void
dwarf_read_array_type (dip)
     struct dieinfo *dip;
{
  struct type *type;
  struct type *utype;
  char *sub;
  char *subend;
  short temp;
  
  if (dip -> at_ordering != ORD_row_major)
    {
      /* FIXME:  Can gdb even handle column major arrays? */
      SQUAWK (("array not row major; not handled correctly"));
    }
  if ((sub = dip -> at_subscr_data) != NULL)
    {
      (void) memcpy (&temp, sub, sizeof (short));
      subend = sub + sizeof (short) + temp;
      sub += sizeof (short);
      type = decode_subscr_data (sub, subend);
      if (type == NULL)
        {
          if ((utype = lookup_utype (dip -> dieref)) == NULL)
            {
              utype = alloc_utype (dip -> dieref, NULL);
            }
          TYPE_CODE (utype) = TYPE_CODE_ARRAY;
          TYPE_TARGET_TYPE (utype) = 
            lookup_fundamental_type (current_objfile, FT_INTEGER);
          TYPE_LENGTH (utype) = 1 * TYPE_LENGTH (TYPE_TARGET_TYPE (utype));
        }
      else
        {
          if ((utype = lookup_utype (dip -> dieref)) == NULL)
            {
              (void) alloc_utype (dip -> dieref, type);
            }
          else
            {
              TYPE_CODE (utype) = TYPE_CODE_ARRAY;
              TYPE_LENGTH (utype) = TYPE_LENGTH (type);
              TYPE_TARGET_TYPE (utype) = TYPE_TARGET_TYPE (type);
            }
        }
    }
}

/*

LOCAL FUNCTION

        read_tag_pointer_type -- read TAG_pointer_type DIE

SYNOPSIS

        static void read_tag_pointer_type (struct dieinfo *dip)

DESCRIPTION

        Extract all information from a TAG_pointer_type DIE and add to
        the user defined type vector.
 */

static void
read_tag_pointer_type (dip)
     struct dieinfo *dip;
{
  struct type *type;
  struct type *utype;
  char *sub;
  char *subend;
  short temp;
  
  type = decode_die_type (dip);
  if ((utype = lookup_utype (dip -> dieref)) == NULL)
    {
      utype = lookup_pointer_type (type);
      (void) alloc_utype (dip -> dieref, utype);
    }
  else
    {
      TYPE_TARGET_TYPE (utype) = type;
      TYPE_POINTER_TYPE (type) = utype;

      /* We assume the machine has only one representation for pointers!  */
      /* FIXME:  This confuses host<->target data representations, and is a
         poor assumption besides. */
      
      TYPE_LENGTH (utype) = sizeof (char *);
      TYPE_CODE (utype) = TYPE_CODE_PTR;
    }
}

/*

LOCAL FUNCTION

        read_subroutine_type -- process TAG_subroutine_type dies

SYNOPSIS

        static void read_subroutine_type (struct dieinfo *dip, char thisdie,
                char *enddie)

DESCRIPTION

        Handle DIES due to C code like:

        struct foo {
            int (*funcp)(int a, long l);  (Generates TAG_subroutine_type DIE)
            int b;
        };

NOTES

        The parameter DIES are currently ignored.  See if gdb has a way to
        include this info in it's type system, and decode them if so.  Is
        this what the type structure's "arg_types" field is for?  (FIXME)
 */

static void
read_subroutine_type (dip, thisdie, enddie)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
{
  struct type *type;            /* Type that this function returns */
  struct type *ftype;           /* Function that returns above type */
  
  /* Decode the type that this subroutine returns */

  type = decode_die_type (dip);

  /* Check to see if we already have a partially constructed user
     defined type for this DIE, from a forward reference. */

  if ((ftype = lookup_utype (dip -> dieref)) == NULL)
    {
      /* This is the first reference to one of these types.  Make
         a new one and place it in the user defined types. */
      ftype = lookup_function_type (type);
      (void) alloc_utype (dip -> dieref, ftype);
    }
  else
    {
      /* We have an existing partially constructed type, so bash it
         into the correct type. */
      TYPE_TARGET_TYPE (ftype) = type;
      TYPE_FUNCTION_TYPE (type) = ftype;
      TYPE_LENGTH (ftype) = 1;
      TYPE_CODE (ftype) = TYPE_CODE_FUNC;
    }
}

/*

LOCAL FUNCTION

        read_enumeration -- process dies which define an enumeration

SYNOPSIS

        static void read_enumeration (struct dieinfo *dip, char *thisdie,
                char *enddie, struct objfile *objfile)

DESCRIPTION

        Given a pointer to a die which begins an enumeration, process all
        the dies that define the members of the enumeration.

NOTES

        Note that we need to call enum_type regardless of whether or not we
        have a symbol, since we might have an enum without a tag name (thus
        no symbol for the tagname).
 */

static void
read_enumeration (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  struct type *type;
  struct symbol *sym;
  
  type = enum_type (dip, objfile);
  if ((sym = new_symbol (dip, objfile)) != NULL)
    {
      SYMBOL_TYPE (sym) = type;
    }
}

/*

LOCAL FUNCTION

        enum_type -- decode and return a type for an enumeration

SYNOPSIS

        static type *enum_type (struct dieinfo *dip, struct objfile *objfile)

DESCRIPTION

        Given a pointer to a die information structure for the die which
        starts an enumeration, process all the dies that define the members
        of the enumeration and return a type pointer for the enumeration.

        At the same time, for each member of the enumeration, create a
        symbol for it with namespace VAR_NAMESPACE and class LOC_CONST,
        and give it the type of the enumeration itself.

NOTES

        Note that the DWARF specification explicitly mandates that enum
        constants occur in reverse order from the source program order,
        for "consistency" and because this ordering is easier for many
        compilers to generate. (Draft 6, sec 3.8.5, Enumeration type
        Entries).  Because gdb wants to see the enum members in program
        source order, we have to ensure that the order gets reversed while
        we are processing them.
 */

static struct type *
enum_type (dip, objfile)
     struct dieinfo *dip;
     struct objfile *objfile;
{
  struct type *type;
  struct nextfield {
    struct nextfield *next;
    struct field field;
  };
  struct nextfield *list = NULL;
  struct nextfield *new;
  int nfields = 0;
  int n;
  char *scan;
  char *listend;
  long ltemp;
  short stemp;
  struct symbol *sym;
  
  if ((type = lookup_utype (dip -> dieref)) == NULL)
    {
      /* No forward references created an empty type, so install one now */
      type = alloc_utype (dip -> dieref, NULL);
    }
  TYPE_CODE (type) = TYPE_CODE_ENUM;
  /* Some compilers try to be helpful by inventing "fake" names for
     anonymous enums, structures, and unions, like "~0fake" or ".0fake".
     Thanks, but no thanks... */
  if (dip -> at_name != NULL
      && *dip -> at_name != '~'
      && *dip -> at_name != '.')
    {
      TYPE_NAME (type) = obconcat (&current_objfile -> type_obstack, "enum",
                                   " ", dip -> at_name);
    }
  if (dip -> at_byte_size != 0)
    {
      TYPE_LENGTH (type) = dip -> at_byte_size;
    }
  if ((scan = dip -> at_element_list) != NULL)
    {
      if (dip -> short_element_list)
        {
          (void) memcpy (&stemp, scan, sizeof (stemp));
          listend = scan + stemp + sizeof (stemp);
          scan += sizeof (stemp);
        }
      else
        {
          (void) memcpy (&ltemp, scan, sizeof (ltemp));
          listend = scan + ltemp + sizeof (ltemp);
          scan += sizeof (ltemp);
        }
      while (scan < listend)
        {
          new = (struct nextfield *) alloca (sizeof (struct nextfield));
          new -> next = list;
          list = new;
          list -> field.type = NULL;
          list -> field.bitsize = 0;
          (void) memcpy (&list -> field.bitpos, scan, sizeof (long));
          scan += sizeof (long);
          list -> field.name = savestring (scan, strlen (scan));
          scan += strlen (scan) + 1;
          nfields++;
          /* Handcraft a new symbol for this enum member. */
          sym = (struct symbol *) obstack_alloc (&objfile->symbol_obstack,
                                                 sizeof (struct symbol));
          (void) memset (sym, 0, sizeof (struct symbol));
          SYMBOL_NAME (sym) = create_name (list -> field.name, &objfile->symbol_obstack);
          SYMBOL_NAMESPACE (sym) = VAR_NAMESPACE;
          SYMBOL_CLASS (sym) = LOC_CONST;
          SYMBOL_TYPE (sym) = type;
          SYMBOL_VALUE (sym) = list -> field.bitpos;
          add_symbol_to_list (sym, list_in_scope);
        }
      /* Now create the vector of fields, and record how big it is. This is
         where we reverse the order, by pulling the members of the list in
         reverse order from how they were inserted.  If we have no fields
         (this is apparently possible in C++) then skip building a field
         vector. */
      if (nfields > 0)
        {
          TYPE_NFIELDS (type) = nfields;
          TYPE_FIELDS (type) = (struct field *)
            obstack_alloc (&objfile->symbol_obstack, sizeof (struct field) * nfields);
          /* Copy the saved-up fields into the field vector.  */
          for (n = 0; (n < nfields) && (list != NULL); list = list -> next)
            {
              TYPE_FIELD (type, n++) = list -> field;
            }   
        }
    }
  return (type);
}

/*

LOCAL FUNCTION

        read_func_scope -- process all dies within a function scope

DESCRIPTION

        Process all dies within a given function scope.  We are passed
        a die information structure pointer DIP for the die which
        starts the function scope, and pointers into the raw die data
        that define the dies within the function scope.

        For now, we ignore lexical block scopes within the function.
        The problem is that AT&T cc does not define a DWARF lexical
        block scope for the function itself, while gcc defines a
        lexical block scope for the function.  We need to think about
        how to handle this difference, or if it is even a problem.
        (FIXME)
 */

static void
read_func_scope (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  register struct context_stack *new;
  
  if (entry_point >= dip -> at_low_pc && entry_point < dip -> at_high_pc)
    {
      entry_scope_lowpc = dip -> at_low_pc;
      entry_scope_highpc = dip -> at_high_pc;
    }
  if (STREQ (dip -> at_name, "main"))   /* FIXME: hardwired name */
    {
      main_scope_lowpc = dip -> at_low_pc;
      main_scope_highpc = dip -> at_high_pc;
    }
  new = push_context (0, dip -> at_low_pc);
  new -> name = new_symbol (dip, objfile);
  list_in_scope = &local_symbols;
  process_dies (thisdie + dip -> dielength, enddie, objfile);
  new = pop_context ();
  /* Make a block for the local symbols within.  */
  finish_block (new -> name, &local_symbols, new -> old_blocks,
                new -> start_addr, dip -> at_high_pc, objfile);
  list_in_scope = &file_symbols;
}

/*

LOCAL FUNCTION

        read_file_scope -- process all dies within a file scope

DESCRIPTION

        Process all dies within a given file scope.  We are passed a
        pointer to the die information structure for the die which
        starts the file scope, and pointers into the raw die data which
        mark the range of dies within the file scope.

        When the partial symbol table is built, the file offset for the line
        number table for each compilation unit is saved in the partial symbol
        table entry for that compilation unit.  As the symbols for each
        compilation unit are read, the line number table is read into memory
        and the variable lnbase is set to point to it.  Thus all we have to
        do is use lnbase to access the line number table for the current
        compilation unit.
 */

static void
read_file_scope (dip, thisdie, enddie, objfile)
     struct dieinfo *dip;
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  struct cleanup *back_to;
  struct symtab *symtab;
  
  if (entry_point >= dip -> at_low_pc && entry_point < dip -> at_high_pc)
    {
      startup_file_start = dip -> at_low_pc;
      startup_file_end = dip -> at_high_pc;
    }
  if (dip -> at_producer != NULL)
    {
      processing_gcc_compilation =
        STREQN (dip -> at_producer, GCC_PRODUCER, strlen (GCC_PRODUCER));
    }
  numutypes = (enddie - thisdie) / 4;
  utypes = (struct type **) xmalloc (numutypes * sizeof (struct type *));
  back_to = make_cleanup (free, utypes);
  (void) memset (utypes, 0, numutypes * sizeof (struct type *));
  start_symtab (dip -> at_name, NULL, dip -> at_low_pc);
  decode_line_numbers (lnbase);
  process_dies (thisdie + dip -> dielength, enddie, objfile);
  symtab = end_symtab (dip -> at_high_pc, 0, 0, objfile);
  /* FIXME:  The following may need to be expanded for other languages */
  switch (dip -> at_language)
    {
      case LANG_C89:
      case LANG_C:
        symtab -> language = language_c;
        break;
      case LANG_C_PLUS_PLUS:
        symtab -> language = language_cplus;
        break;
      default:
        ;
    }
  do_cleanups (back_to);
  utypes = NULL;
  numutypes = 0;
}

/*

LOCAL FUNCTION

        process_dies -- process a range of DWARF Information Entries

SYNOPSIS

        static void process_dies (char *thisdie, char *enddie,
                                  struct objfile *objfile)

DESCRIPTION

        Process all DIE's in a specified range.  May be (and almost
        certainly will be) called recursively.
 */

static void
process_dies (thisdie, enddie, objfile)
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  char *nextdie;
  struct dieinfo di;
  
  while (thisdie < enddie)
    {
      basicdieinfo (&di, thisdie);
      if (di.dielength < sizeof (long))
        {
          break;
        }
      else if (di.dietag == TAG_padding)
        {
          nextdie = thisdie + di.dielength;
        }
      else
        {
          completedieinfo (&di);
          if (di.at_sibling != 0)
            {
              nextdie = dbbase + di.at_sibling - dbroff;
            }
          else
            {
              nextdie = thisdie + di.dielength;
            }
          switch (di.dietag)
            {
            case TAG_compile_unit:
              read_file_scope (&di, thisdie, nextdie, objfile);
              break;
            case TAG_global_subroutine:
            case TAG_subroutine:
              if (di.has_at_low_pc)
                {
                  read_func_scope (&di, thisdie, nextdie, objfile);
                }
              break;
            case TAG_lexical_block:
              read_lexical_block_scope (&di, thisdie, nextdie, objfile);
              break;
            case TAG_structure_type:
            case TAG_union_type:
              read_structure_scope (&di, thisdie, nextdie, objfile);
              break;
            case TAG_enumeration_type:
              read_enumeration (&di, thisdie, nextdie, objfile);
              break;
            case TAG_subroutine_type:
              read_subroutine_type (&di, thisdie, nextdie);
              break;
            case TAG_array_type:
              dwarf_read_array_type (&di);
              break;
            case TAG_pointer_type:
              read_tag_pointer_type (&di);
              break;
            default:
              (void) new_symbol (&di, objfile);
              break;
            }
        }
      thisdie = nextdie;
    }
}

/*

LOCAL FUNCTION

        decode_line_numbers -- decode a line number table fragment

SYNOPSIS

        static void decode_line_numbers (char *tblscan, char *tblend,
                long length, long base, long line, long pc)

DESCRIPTION

        Translate the DWARF line number information to gdb form.

        The ".line" section contains one or more line number tables, one for
        each ".line" section from the objects that were linked.

        The AT_stmt_list attribute for each TAG_source_file entry in the
        ".debug" section contains the offset into the ".line" section for the
        start of the table for that file.

        The table itself has the following structure:

        <table length><base address><source statement entry>
        4 bytes       4 bytes       10 bytes

        The table length is the total size of the table, including the 4 bytes
        for the length information.

        The base address is the address of the first instruction generated
        for the source file.

        Each source statement entry has the following structure:

        <line number><statement position><address delta>
        4 bytes      2 bytes             4 bytes

        The line number is relative to the start of the file, starting with
        line 1.

        The statement position either -1 (0xFFFF) or the number of characters
        from the beginning of the line to the beginning of the statement.

        The address delta is the difference between the base address and
        the address of the first instruction for the statement.

        Note that we must copy the bytes from the packed table to our local
        variables before attempting to use them, to avoid alignment problems
        on some machines, particularly RISC processors.

BUGS

        Does gdb expect the line numbers to be sorted?  They are now by
        chance/luck, but are not required to be.  (FIXME)

        The line with number 0 is unused, gdb apparently can discover the
        span of the last line some other way. How?  (FIXME)
 */

static void
decode_line_numbers (linetable)
     char *linetable;
{
  char *tblscan;
  char *tblend;
  long length;
  long base;
  long line;
  long pc;
  
  if (linetable != NULL)
    {
      tblscan = tblend = linetable;
      (void) memcpy (&length, tblscan, sizeof (long));
      tblscan += sizeof (long);
      tblend += length;
      (void) memcpy (&base, tblscan, sizeof (long));
      base += baseaddr;
      tblscan += sizeof (long);
      while (tblscan < tblend)
        {
          (void) memcpy (&line, tblscan, sizeof (long));
          tblscan += sizeof (long) + sizeof (short);
          (void) memcpy (&pc, tblscan, sizeof (long));
          tblscan += sizeof (long);
          pc += base;
          if (line > 0)
            {
              record_line (current_subfile, line, pc);
            }
        }
    }
}

/*

LOCAL FUNCTION

        locval -- compute the value of a location attribute

SYNOPSIS

        static int locval (char *loc)

DESCRIPTION

        Given pointer to a string of bytes that define a location, compute
        the location and return the value.

        When computing values involving the current value of the frame pointer,
        the value zero is used, which results in a value relative to the frame
        pointer, rather than the absolute value.  This is what GDB wants
        anyway.
    
        When the result is a register number, the global isreg flag is set,
        otherwise it is cleared.  This is a kludge until we figure out a better
        way to handle the problem.  Gdb's design does not mesh well with the
        DWARF notion of a location computing interpreter, which is a shame
        because the flexibility goes unused.

NOTES

        Note that stack[0] is unused except as a default error return.
        Note that stack overflow is not yet handled.
 */

static int
locval (loc)
     char *loc;
{
  unsigned short nbytes;
  auto int stack[64];
  int stacki;
  char *end;
  long regno;
  
  (void) memcpy (&nbytes, loc, sizeof (short));
  end = loc + sizeof (short) + nbytes;
  stacki = 0;
  stack[stacki] = 0;
  isreg = 0;
  offreg = 0;
  for (loc += sizeof (short); loc < end; loc += sizeof (long))
    {
      switch (*loc++) {
      case 0:
        /* error */
        loc = end;
        break;
      case OP_REG:
        /* push register (number) */
        (void) memcpy (&stack[++stacki], loc, sizeof (long));
        isreg = 1;
        break;
      case OP_BASEREG:
        /* push value of register (number) */
        /* Actually, we compute the value as if register has 0 */
        offreg = 1;
        (void) memcpy (&regno, loc, sizeof (long));
        if (regno == R_FP)
          {
            stack[++stacki] = 0;
          }
        else
          {
            stack[++stacki] = 0;
            SQUAWK (("BASEREG %d not handled!", regno));
          }
        break;
      case OP_ADDR:
        /* push address (relocated address) */
        (void) memcpy (&stack[++stacki], loc, sizeof (long));
        break;
      case OP_CONST:
        /* push constant (number) */
        (void) memcpy (&stack[++stacki], loc, sizeof (long));
        break;
      case OP_DEREF2:
        /* pop, deref and push 2 bytes (as a long) */
        SQUAWK (("OP_DEREF2 address %#x not handled", stack[stacki]));
        break;
      case OP_DEREF4:   /* pop, deref and push 4 bytes (as a long) */
        SQUAWK (("OP_DEREF4 address %#x not handled", stack[stacki]));
        break;
      case OP_ADD:      /* pop top 2 items, add, push result */
        stack[stacki - 1] += stack[stacki];
        stacki--;
        break;
      }
    }
  return (stack[stacki]);
}

/*

LOCAL FUNCTION

        read_ofile_symtab -- build a full symtab entry from chunk of DIE's

SYNOPSIS

        static struct symtab *read_ofile_symtab (struct partial_symtab *pst)

DESCRIPTION

        When expanding a partial symbol table entry to a full symbol table
        entry, this is the function that gets called to read in the symbols
        for the compilation unit.

        Returns a pointer to the newly constructed symtab (which is now
        the new first one on the objfile's symtab list).
 */

static struct symtab *
read_ofile_symtab (pst)
     struct partial_symtab *pst;
{
  struct cleanup *back_to;
  long lnsize;
  int foffset;
  bfd *abfd;

  abfd = pst -> objfile -> obfd;
  current_objfile = pst -> objfile;

  /* Allocate a buffer for the entire chunk of DIE's for this compilation
     unit, seek to the location in the file, and read in all the DIE's. */

  diecount = 0;
  dbbase = xmalloc (DBLENGTH(pst));
  dbroff = DBROFF(pst);
  foffset = DBFOFF(pst) + dbroff;
  baseaddr = pst -> addr;
  if (bfd_seek (abfd, foffset, 0) ||
      (bfd_read (dbbase, DBLENGTH(pst), 1, abfd) != DBLENGTH(pst)))
    {
      free (dbbase);
      error ("can't read DWARF data");
    }
  back_to = make_cleanup (free, dbbase);

  /* If there is a line number table associated with this compilation unit
     then read the first long word from the line number table fragment, which
     contains the size of the fragment in bytes (including the long word
     itself).  Allocate a buffer for the fragment and read it in for future
     processing. */

  lnbase = NULL;
  if (LNFOFF (pst))
    {
      if (bfd_seek (abfd, LNFOFF (pst), 0) ||
          (bfd_read (&lnsize, sizeof(long), 1, abfd) != sizeof(long)))
        {
          error ("can't read DWARF line number table size");
        }
      lnbase = xmalloc (lnsize);
      if (bfd_seek (abfd, LNFOFF (pst), 0) ||
          (bfd_read (lnbase, lnsize, 1, abfd) != lnsize))
        {
          free (lnbase);
          error ("can't read DWARF line numbers");
        }
      make_cleanup (free, lnbase);
    }

  process_dies (dbbase, dbbase + DBLENGTH(pst), pst -> objfile);
  do_cleanups (back_to);
  current_objfile = NULL;
  return (pst -> objfile -> symtabs);
}

/*

LOCAL FUNCTION

        psymtab_to_symtab_1 -- do grunt work for building a full symtab entry

SYNOPSIS

        static void psymtab_to_symtab_1 (struct partial_symtab *pst)

DESCRIPTION

        Called once for each partial symbol table entry that needs to be
        expanded into a full symbol table entry.

*/

static void
psymtab_to_symtab_1 (pst)
     struct partial_symtab *pst;
{
  int i;
  
  if (pst != NULL)
    {
      if (pst->readin)
        {
          warning ("Psymtab for %s already read in.  Shouldn't happen.",
                   pst -> filename);
        }
      else
        {
          /* Read in all partial symtabs on which this one is dependent */
          for (i = 0; i < pst -> number_of_dependencies; i++)
            {
              if (!pst -> dependencies[i] -> readin)
                {
                  /* Inform about additional files that need to be read in. */
                  if (info_verbose)
                    {
                      fputs_filtered (" ", stdout);
                      wrap_here ("");
                      fputs_filtered ("and ", stdout);
                      wrap_here ("");
                      printf_filtered ("%s...",
                                       pst -> dependencies[i] -> filename);
                      wrap_here ("");
                      fflush (stdout);          /* Flush output */
                    }
                  psymtab_to_symtab_1 (pst -> dependencies[i]);
                }
            }     
          if (DBLENGTH (pst))           /* Otherwise it's a dummy */
            {
              pst -> symtab = read_ofile_symtab (pst);
              if (info_verbose)
                {
                  printf_filtered ("%d DIE's, sorting...", diecount);
                  wrap_here ("");
                  fflush (stdout);
                }
              sort_symtab_syms (pst -> symtab);
            }
          pst -> readin = 1;
        }
    }
}

/*

LOCAL FUNCTION

        dwarf_psymtab_to_symtab -- build a full symtab entry from partial one

SYNOPSIS

        static void dwarf_psymtab_to_symtab (struct partial_symtab *pst)

DESCRIPTION

        This is the DWARF support entry point for building a full symbol
        table entry from a partial symbol table entry.  We are passed a
        pointer to the partial symbol table entry that needs to be expanded.

*/

static void
dwarf_psymtab_to_symtab (pst)
     struct partial_symtab *pst;
{

  if (pst != NULL)
    {
      if (pst -> readin)
        {
          warning ("Psymtab for %s already read in.  Shouldn't happen.",
                   pst -> filename);
        }
      else
        {
          if (DBLENGTH (pst) || pst -> number_of_dependencies)
            {
              /* Print the message now, before starting serious work, to avoid
                 disconcerting pauses.  */
              if (info_verbose)
                {
                  printf_filtered ("Reading in symbols for %s...",
                                   pst -> filename);
                  fflush (stdout);
                }
              
              psymtab_to_symtab_1 (pst);
              
#if 0         /* FIXME:  Check to see what dbxread is doing here and see if
                 we need to do an equivalent or is this something peculiar to
                 stabs/a.out format.
                 Match with global symbols.  This only needs to be done once,
                 after all of the symtabs and dependencies have been read in.
                 */
              scan_file_globals (pst -> objfile);
#endif
              
              /* Finish up the verbose info message.  */
              if (info_verbose)
                {
                  printf_filtered ("done.\n");
                  fflush (stdout);
                }
            }
        }
    }
}

/*

LOCAL FUNCTION

        init_psymbol_list -- initialize storage for partial symbols

SYNOPSIS

        static void init_psymbol_list (struct objfile *objfile, int total_symbols)

DESCRIPTION

        Initializes storage for all of the partial symbols that will be
        created by dwarf_build_psymtabs and subsidiaries.
 */

static void
init_psymbol_list (objfile, total_symbols)
     struct objfile *objfile;
     int total_symbols;
{
  /* Free any previously allocated psymbol lists.  */
  
  if (objfile -> global_psymbols.list)
    {
      (*objfile -> free) (objfile -> global_psymbols.list);
    }
  if (objfile -> static_psymbols.list)
    {
      (*objfile -> free) (objfile -> static_psymbols.list);
    }
  
  /* Current best guess is that there are approximately a twentieth
     of the total symbols (in a debugging file) are global or static
     oriented symbols */
  
  objfile -> global_psymbols.size = total_symbols / 10;
  objfile -> static_psymbols.size = total_symbols / 10;
  objfile -> global_psymbols.next =
    objfile -> global_psymbols.list = (struct partial_symbol *)
      (*objfile -> xmalloc) (objfile -> global_psymbols.size
                             * sizeof (struct partial_symbol));
  objfile -> static_psymbols.next =
    objfile -> static_psymbols.list = (struct partial_symbol *)
      (*objfile -> xmalloc) (objfile -> static_psymbols.size
                             * sizeof (struct partial_symbol));
}

/*

LOCAL FUNCTION

        add_enum_psymbol -- add enumeration members to partial symbol table

DESCRIPTION

        Given pointer to a DIE that is known to be for an enumeration,
        extract the symbolic names of the enumeration members and add
        partial symbols for them.
*/

static void
add_enum_psymbol (dip, objfile)
     struct dieinfo *dip;
     struct objfile *objfile;
{
  char *scan;
  char *listend;
  long ltemp;
  short stemp;
  
  if ((scan = dip -> at_element_list) != NULL)
    {
      if (dip -> short_element_list)
        {
          (void) memcpy (&stemp, scan, sizeof (stemp));
          listend = scan + stemp + sizeof (stemp);
          scan += sizeof (stemp);
        }
      else
        {
          (void) memcpy (&ltemp, scan, sizeof (ltemp));
          listend = scan + ltemp + sizeof (ltemp);
          scan += sizeof (ltemp);
        }
      while (scan < listend)
        {
          scan += sizeof (long);
          ADD_PSYMBOL_TO_LIST (scan, strlen (scan), VAR_NAMESPACE, LOC_CONST,
                               objfile -> static_psymbols, 0);
          scan += strlen (scan) + 1;
        }
    }
}

/*

LOCAL FUNCTION

        add_partial_symbol -- add symbol to partial symbol table

DESCRIPTION

        Given a DIE, if it is one of the types that we want to
        add to a partial symbol table, finish filling in the die info
        and then add a partial symbol table entry for it.

*/

static void
add_partial_symbol (dip, objfile)
     struct dieinfo *dip;
     struct objfile *objfile;
{
  switch (dip -> dietag)
    {
    case TAG_global_subroutine:
      record_minimal_symbol (dip -> at_name, dip -> at_low_pc, mst_text,
                            objfile);
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           VAR_NAMESPACE, LOC_BLOCK,
                           objfile -> global_psymbols,
                           dip -> at_low_pc);
      break;
    case TAG_global_variable:
      record_minimal_symbol (dip -> at_name, locval (dip -> at_location),
                            mst_data, objfile);
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           VAR_NAMESPACE, LOC_STATIC,
                           objfile -> global_psymbols,
                           0);
      break;
    case TAG_subroutine:
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           VAR_NAMESPACE, LOC_BLOCK,
                           objfile -> static_psymbols,
                           dip -> at_low_pc);
      break;
    case TAG_local_variable:
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           VAR_NAMESPACE, LOC_STATIC,
                           objfile -> static_psymbols,
                           0);
      break;
    case TAG_typedef:
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           VAR_NAMESPACE, LOC_TYPEDEF,
                           objfile -> static_psymbols,
                           0);
      break;
    case TAG_structure_type:
    case TAG_union_type:
      ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                           STRUCT_NAMESPACE, LOC_TYPEDEF,
                           objfile -> static_psymbols,
                           0);
      break;
    case TAG_enumeration_type:
      if (dip -> at_name)
        {
          ADD_PSYMBOL_TO_LIST (dip -> at_name, strlen (dip -> at_name),
                               STRUCT_NAMESPACE, LOC_TYPEDEF,
                               objfile -> static_psymbols,
                               0);
        }
      add_enum_psymbol (dip, objfile);
      break;
    }
}

/*

LOCAL FUNCTION

        scan_partial_symbols -- scan DIE's within a single compilation unit

DESCRIPTION

        Process the DIE's within a single compilation unit, looking for
        interesting DIE's that contribute to the partial symbol table entry
        for this compilation unit.  Since we cannot follow any sibling
        chains without reading the complete DIE info for every DIE,
        it is probably faster to just sequentially check each one to
        see if it is one of the types we are interested in, and if so,
        then extract all the attributes info and generate a partial
        symbol table entry.

NOTES

        Don't attempt to add anonymous structures or unions since they have
        no name.  Anonymous enumerations however are processed, because we
        want to extract their member names (the check for a tag name is
        done later).

        Also, for variables and subroutines, check that this is the place
        where the actual definition occurs, rather than just a reference
        to an external.
 */

static void
scan_partial_symbols (thisdie, enddie, objfile)
     char *thisdie;
     char *enddie;
     struct objfile *objfile;
{
  char *nextdie;
  struct dieinfo di;
  
  while (thisdie < enddie)
    {
      basicdieinfo (&di, thisdie);
      if (di.dielength < sizeof (long))
        {
          break;
        }
      else
        {
          nextdie = thisdie + di.dielength;
          /* To avoid getting complete die information for every die, we
             only do it (below) for the cases we are interested in. */
          switch (di.dietag)
            {
            case TAG_global_subroutine:
            case TAG_subroutine:
            case TAG_global_variable:
            case TAG_local_variable:
              completedieinfo (&di);
              if (di.at_name && (di.has_at_low_pc || di.at_location))
                {
                  add_partial_symbol (&di, objfile);
                }
              break;
            case TAG_typedef:
            case TAG_structure_type:
            case TAG_union_type:
              completedieinfo (&di);
              if (di.at_name)
                {
                  add_partial_symbol (&di, objfile);
                }
              break;
            case TAG_enumeration_type:
              completedieinfo (&di);
              add_partial_symbol (&di, objfile);
              break;
            }
        }
      thisdie = nextdie;
    }
}

/*

LOCAL FUNCTION

        scan_compilation_units -- build a psymtab entry for each compilation

DESCRIPTION

        This is the top level dwarf parsing routine for building partial
        symbol tables.

        It scans from the beginning of the DWARF table looking for the first
        TAG_compile_unit DIE, and then follows the sibling chain to locate
        each additional TAG_compile_unit DIE.
   
        For each TAG_compile_unit DIE it creates a partial symtab structure,
        calls a subordinate routine to collect all the compilation unit's
        global DIE's, file scope DIEs, typedef DIEs, etc, and then links the
        new partial symtab structure into the partial symbol table.  It also
        records the appropriate information in the partial symbol table entry
        to allow the chunk of DIE's and line number table for this compilation
        unit to be located and re-read later, to generate a complete symbol
        table entry for the compilation unit.

        Thus it effectively partitions up a chunk of DIE's for multiple
        compilation units into smaller DIE chunks and line number tables,
        and associates them with a partial symbol table entry.

NOTES

        If any compilation unit has no line number table associated with
        it for some reason (a missing at_stmt_list attribute, rather than
        just one with a value of zero, which is valid) then we ensure that
        the recorded file offset is zero so that the routine which later
        reads line number table fragments knows that there is no fragment
        to read.

RETURNS

        Returns no value.

 */

static void
scan_compilation_units (filename, thisdie, enddie, dbfoff, lnoffset, objfile)
     char *filename;
     char *thisdie;
     char *enddie;
     unsigned int dbfoff;
     unsigned int lnoffset;
     struct objfile *objfile;
{
  char *nextdie;
  struct dieinfo di;
  struct partial_symtab *pst;
  int culength;
  int curoff;
  int curlnoffset;

  while (thisdie < enddie)
    {
      basicdieinfo (&di, thisdie);
      if (di.dielength < sizeof (long))
        {
          break;
        }
      else if (di.dietag != TAG_compile_unit)
        {
          nextdie = thisdie + di.dielength;
        }
      else
        {
          completedieinfo (&di);
          if (di.at_sibling != 0)
            {
              nextdie = dbbase + di.at_sibling - dbroff;
            }
          else
            {
              nextdie = thisdie + di.dielength;
            }
          curoff = thisdie - dbbase;
          culength = nextdie - thisdie;
          curlnoffset = di.has_at_stmt_list ? lnoffset + di.at_stmt_list : 0;

          /* First allocate a new partial symbol table structure */

          pst = start_psymtab_common (objfile, baseaddr, di.at_name,
                                      di.at_low_pc,
                                      objfile -> global_psymbols.next,
                                      objfile -> static_psymbols.next);

          pst -> texthigh = di.at_high_pc;
          pst -> read_symtab_private = (char *)
              obstack_alloc (&objfile -> psymbol_obstack,
                             sizeof (struct dwfinfo));
          DBFOFF (pst) = dbfoff;
          DBROFF (pst) = curoff;
          DBLENGTH (pst) = culength;
          LNFOFF (pst)  = curlnoffset;
          pst -> read_symtab = dwarf_psymtab_to_symtab;

          /* Now look for partial symbols */

          scan_partial_symbols (thisdie + di.dielength, nextdie, objfile);

          pst -> n_global_syms = objfile -> global_psymbols.next -
            (objfile -> global_psymbols.list + pst -> globals_offset);
          pst -> n_static_syms = objfile -> static_psymbols.next - 
            (objfile -> static_psymbols.list + pst -> statics_offset);
          sort_pst_symbols (pst);
          /* If there is already a psymtab or symtab for a file of this name,
             remove it. (If there is a symtab, more drastic things also
             happen.)  This happens in VxWorks.  */
          free_named_symtabs (pst -> filename);
        }
      thisdie = nextdie;      
    }
}

/*

LOCAL FUNCTION

        new_symbol -- make a symbol table entry for a new symbol

SYNOPSIS

        static struct symbol *new_symbol (struct dieinfo *dip,
                                          struct objfile *objfile)

DESCRIPTION

        Given a pointer to a DWARF information entry, figure out if we need
        to make a symbol table entry for it, and if so, create a new entry
        and return a pointer to it.
 */

static struct symbol *
new_symbol (dip, objfile)
     struct dieinfo *dip;
     struct objfile *objfile;
{
  struct symbol *sym = NULL;
  
  if (dip -> at_name != NULL)
    {
      sym = (struct symbol *) obstack_alloc (&objfile -> symbol_obstack,
                                             sizeof (struct symbol));
      (void) memset (sym, 0, sizeof (struct symbol));
      SYMBOL_NAME (sym) = create_name (dip -> at_name, &objfile->symbol_obstack);
      /* default assumptions */
      SYMBOL_NAMESPACE (sym) = VAR_NAMESPACE;
      SYMBOL_CLASS (sym) = LOC_STATIC;
      SYMBOL_TYPE (sym) = decode_die_type (dip);
      switch (dip -> dietag)
        {
        case TAG_label:
          SYMBOL_VALUE (sym) = dip -> at_low_pc;
          SYMBOL_CLASS (sym) = LOC_LABEL;
          break;
        case TAG_global_subroutine:
        case TAG_subroutine:
          SYMBOL_VALUE (sym) = dip -> at_low_pc;
          SYMBOL_TYPE (sym) = lookup_function_type (SYMBOL_TYPE (sym));
          SYMBOL_CLASS (sym) = LOC_BLOCK;
          if (dip -> dietag == TAG_global_subroutine)
            {
              add_symbol_to_list (sym, &global_symbols);
            }
          else
            {
              add_symbol_to_list (sym, list_in_scope);
            }
          break;
        case TAG_global_variable:
          if (dip -> at_location != NULL)
            {
              SYMBOL_VALUE (sym) = locval (dip -> at_location);
              add_symbol_to_list (sym, &global_symbols);
              SYMBOL_CLASS (sym) = LOC_STATIC;
              SYMBOL_VALUE (sym) += baseaddr;
            }
          break;
        case TAG_local_variable:
          if (dip -> at_location != NULL)
            {
              SYMBOL_VALUE (sym) = locval (dip -> at_location);
              add_symbol_to_list (sym, list_in_scope);
              if (isreg)
                {
                  SYMBOL_CLASS (sym) = LOC_REGISTER;
                }
              else if (offreg)
                {
                  SYMBOL_CLASS (sym) = LOC_LOCAL;
                }
              else
                {
                  SYMBOL_CLASS (sym) = LOC_STATIC;
                  SYMBOL_VALUE (sym) += baseaddr;
                }
            }
          break;
        case TAG_formal_parameter:
          if (dip -> at_location != NULL)
            {
              SYMBOL_VALUE (sym) = locval (dip -> at_location);
            }
          add_symbol_to_list (sym, list_in_scope);
          if (isreg)
            {
              SYMBOL_CLASS (sym) = LOC_REGPARM;
            }
          else
            {
              SYMBOL_CLASS (sym) = LOC_ARG;
            }
          break;
        case TAG_unspecified_parameters:
          /* From varargs functions; gdb doesn't seem to have any interest in
             this information, so just ignore it for now. (FIXME?) */
          break;
        case TAG_structure_type:
        case TAG_union_type:
        case TAG_enumeration_type:
          SYMBOL_CLASS (sym) = LOC_TYPEDEF;
          SYMBOL_NAMESPACE (sym) = STRUCT_NAMESPACE;
          add_symbol_to_list (sym, list_in_scope);
          break;
        case TAG_typedef:
          SYMBOL_CLASS (sym) = LOC_TYPEDEF;
          SYMBOL_NAMESPACE (sym) = VAR_NAMESPACE;
          add_symbol_to_list (sym, list_in_scope);
          break;
        default:
          /* Not a tag we recognize.  Hopefully we aren't processing trash
             data, but since we must specifically ignore things we don't
             recognize, there is nothing else we should do at this point. */
          break;
        }
    }
  return (sym);
}

/*

LOCAL FUNCTION

        decode_mod_fund_type -- decode a modified fundamental type

SYNOPSIS

        static struct type *decode_mod_fund_type (char *typedata)

DESCRIPTION

        Decode a block of data containing a modified fundamental
        type specification.  TYPEDATA is a pointer to the block,
        which consists of a two byte length, containing the size
        of the rest of the block.  At the end of the block is a
        two byte value that gives the fundamental type.  Everything
        in between are type modifiers.

        We simply compute the number of modifiers and call the general
        function decode_modified_type to do the actual work.
*/

static struct type *
decode_mod_fund_type (typedata)
     char *typedata;
{
  struct type *typep = NULL;
  unsigned short modcount;
  unsigned char *modifiers;
  
  /* Get the total size of the block, exclusive of the size itself */
  (void) memcpy (&modcount, typedata, sizeof (short));
  /* Deduct the size of the fundamental type bytes at the end of the block. */
  modcount -= sizeof (short);
  /* Skip over the two size bytes at the beginning of the block. */
  modifiers = (unsigned char *) typedata + sizeof (short);
  /* Now do the actual decoding */
  typep = decode_modified_type (modifiers, modcount, AT_mod_fund_type);
  return (typep);
}

/*

LOCAL FUNCTION

        decode_mod_u_d_type -- decode a modified user defined type

SYNOPSIS

        static struct type *decode_mod_u_d_type (char *typedata)

DESCRIPTION

        Decode a block of data containing a modified user defined
        type specification.  TYPEDATA is a pointer to the block,
        which consists of a two byte length, containing the size
        of the rest of the block.  At the end of the block is a
        four byte value that gives a reference to a user defined type.
        Everything in between are type modifiers.

        We simply compute the number of modifiers and call the general
        function decode_modified_type to do the actual work.
*/

static struct type *
decode_mod_u_d_type (typedata)
     char *typedata;
{
  struct type *typep = NULL;
  unsigned short modcount;
  unsigned char *modifiers;
  
  /* Get the total size of the block, exclusive of the size itself */
  (void) memcpy (&modcount, typedata, sizeof (short));
  /* Deduct the size of the reference type bytes at the end of the block. */
  modcount -= sizeof (long);
  /* Skip over the two size bytes at the beginning of the block. */
  modifiers = (unsigned char *) typedata + sizeof (short);
  /* Now do the actual decoding */
  typep = decode_modified_type (modifiers, modcount, AT_mod_u_d_type);
  return (typep);
}

/*

LOCAL FUNCTION

        decode_modified_type -- decode modified user or fundamental type

SYNOPSIS

        static struct type *decode_modified_type (unsigned char *modifiers,
            unsigned short modcount, int mtype)

DESCRIPTION

        Decode a modified type, either a modified fundamental type or
        a modified user defined type.  MODIFIERS is a pointer to the
        block of bytes that define MODCOUNT modifiers.  Immediately
        following the last modifier is a short containing the fundamental
        type or a long containing the reference to the user defined
        type.  Which one is determined by MTYPE, which is either
        AT_mod_fund_type or AT_mod_u_d_type to indicate what modified
        type we are generating.

        We call ourself recursively to generate each modified type,`
        until MODCOUNT reaches zero, at which point we have consumed
        all the modifiers and generate either the fundamental type or
        user defined type.  When the recursion unwinds, each modifier
        is applied in turn to generate the full modified type.

NOTES

        If we find a modifier that we don't recognize, and it is not one
        of those reserved for application specific use, then we issue a
        warning and simply ignore the modifier.

BUGS

        We currently ignore MOD_const and MOD_volatile.  (FIXME)

 */

static struct type *
decode_modified_type (modifiers, modcount, mtype)
     unsigned char *modifiers;
     unsigned int modcount;
     int mtype;
{
  struct type *typep = NULL;
  unsigned short fundtype;
  DIEREF dieref;
  unsigned char modifier;
  
  if (modcount == 0)
    {
      switch (mtype)
        {
        case AT_mod_fund_type:
          (void) memcpy (&fundtype, modifiers, sizeof (short));
          typep = decode_fund_type (fundtype);
          break;
        case AT_mod_u_d_type:
          (void) memcpy (&dieref, modifiers, sizeof (DIEREF));
          if ((typep = lookup_utype (dieref)) == NULL)
            {
              typep = alloc_utype (dieref, NULL);
            }
          break;
        default:
          SQUAWK (("botched modified type decoding (mtype 0x%x)", mtype));
          typep = lookup_fundamental_type (current_objfile, FT_INTEGER);
          break;
        }
    }
  else
    {
      modifier = *modifiers++;
      typep = decode_modified_type (modifiers, --modcount, mtype);
      switch (modifier)
        {
        case MOD_pointer_to:
          typep = lookup_pointer_type (typep);
          break;
        case MOD_reference_to:
          typep = lookup_reference_type (typep);
          break;
        case MOD_const:
          SQUAWK (("type modifier 'const' ignored"));   /* FIXME */
          break;
        case MOD_volatile:
          SQUAWK (("type modifier 'volatile' ignored"));        /* FIXME */
          break;
        default:
          if (!(MOD_lo_user <= modifier && modifier <= MOD_hi_user))
            {
              SQUAWK (("unknown type modifier %u", modifier));
            }
          break;
        }
    }
  return (typep);
}

/*

LOCAL FUNCTION

        decode_fund_type -- translate basic DWARF type to gdb base type

DESCRIPTION

        Given an integer that is one of the fundamental DWARF types,
        translate it to one of the basic internal gdb types and return
        a pointer to the appropriate gdb type (a "struct type *").

NOTES

        If we encounter a fundamental type that we are unprepared to
        deal with, and it is not in the range of those types defined
        as application specific types, then we issue a warning and
        treat the type as an "int".
*/

static struct type *
decode_fund_type (fundtype)
     unsigned int fundtype;
{
  struct type *typep = NULL;
  
  switch (fundtype)
    {

    case FT_void:
      typep = lookup_fundamental_type (current_objfile, FT_VOID);
      break;
    
    case FT_boolean:            /* Was FT_set in AT&T version */
      typep = lookup_fundamental_type (current_objfile, FT_BOOLEAN);
      break;

    case FT_pointer:            /* (void *) */
      typep = lookup_fundamental_type (current_objfile, FT_VOID);
      typep = lookup_pointer_type (typep);
      break;
    
    case FT_char:
      typep = lookup_fundamental_type (current_objfile, FT_CHAR);
      break;
    
    case FT_signed_char:
      typep = lookup_fundamental_type (current_objfile, FT_SIGNED_CHAR);
      break;

    case FT_unsigned_char:
      typep = lookup_fundamental_type (current_objfile, FT_UNSIGNED_CHAR);
      break;
    
    case FT_short:
      typep = lookup_fundamental_type (current_objfile, FT_SHORT);
      break;

    case FT_signed_short:
      typep = lookup_fundamental_type (current_objfile, FT_SIGNED_SHORT);
      break;
    
    case FT_unsigned_short:
      typep = lookup_fundamental_type (current_objfile, FT_UNSIGNED_SHORT);
      break;
    
    case FT_integer:
      typep = lookup_fundamental_type (current_objfile, FT_INTEGER);
      break;

    case FT_signed_integer:
      typep = lookup_fundamental_type (current_objfile, FT_SIGNED_INTEGER);
      break;
    
    case FT_unsigned_integer:
      typep = lookup_fundamental_type (current_objfile, FT_UNSIGNED_INTEGER);
      break;
    
    case FT_long:
      typep = lookup_fundamental_type (current_objfile, FT_LONG);
      break;

    case FT_signed_long:
      typep = lookup_fundamental_type (current_objfile, FT_SIGNED_LONG);
      break;
    
    case FT_unsigned_long:
      typep = lookup_fundamental_type (current_objfile, FT_UNSIGNED_LONG);
      break;
    
    case FT_long_long:
      typep = lookup_fundamental_type (current_objfile, FT_LONG_LONG);
      break;

    case FT_signed_long_long:
      typep = lookup_fundamental_type (current_objfile, FT_SIGNED_LONG_LONG);
      break;

    case FT_unsigned_long_long:
      typep = lookup_fundamental_type (current_objfile, FT_UNSIGNED_LONG_LONG);
      break;

    case FT_float:
      typep = lookup_fundamental_type (current_objfile, FT_FLOAT);
      break;
    
    case FT_dbl_prec_float:
      typep = lookup_fundamental_type (current_objfile, FT_DBL_PREC_FLOAT);
      break;
    
    case FT_ext_prec_float:
      typep = lookup_fundamental_type (current_objfile, FT_EXT_PREC_FLOAT);
      break;
    
    case FT_complex:
      typep = lookup_fundamental_type (current_objfile, FT_COMPLEX);
      break;
    
    case FT_dbl_prec_complex:
      typep = lookup_fundamental_type (current_objfile, FT_DBL_PREC_COMPLEX);
      break;
    
    case FT_ext_prec_complex:
      typep = lookup_fundamental_type (current_objfile, FT_EXT_PREC_COMPLEX);
      break;
    
    }

  if ((typep == NULL) && !(FT_lo_user <= fundtype && fundtype <= FT_hi_user))
    {
      SQUAWK (("unexpected fundamental type 0x%x", fundtype));
      typep = lookup_fundamental_type (current_objfile, FT_VOID);
    }
    
  return (typep);
}

/*

LOCAL FUNCTION

        create_name -- allocate a fresh copy of a string on an obstack

DESCRIPTION

        Given a pointer to a string and a pointer to an obstack, allocates
        a fresh copy of the string on the specified obstack.

*/

static char *
create_name (name, obstackp)
     char *name;
     struct obstack *obstackp;
{
  int length;
  char *newname;

  length = strlen (name) + 1;
  newname = (char *) obstack_alloc (obstackp, length);
  (void) strcpy (newname, name);
  return (newname);
}

/*

LOCAL FUNCTION

        basicdieinfo -- extract the minimal die info from raw die data

SYNOPSIS

        void basicdieinfo (char *diep, struct dieinfo *dip)

DESCRIPTION

        Given a pointer to raw DIE data, and a pointer to an instance of a
        die info structure, this function extracts the basic information
        from the DIE data required to continue processing this DIE, along
        with some bookkeeping information about the DIE.

        The information we absolutely must have includes the DIE tag,
        and the DIE length.  If we need the sibling reference, then we
        will have to call completedieinfo() to process all the remaining
        DIE information.

        Note that since there is no guarantee that the data is properly
        aligned in memory for the type of access required (indirection
        through anything other than a char pointer), we use memcpy to
        shuffle data items larger than a char.  Possibly inefficient, but
        quite portable.

        We also take care of some other basic things at this point, such
        as ensuring that the instance of the die info structure starts
        out completely zero'd and that curdie is initialized for use
        in error reporting if we have a problem with the current die.

NOTES

        All DIE's must have at least a valid length, thus the minimum
        DIE size is sizeof (long).  In order to have a valid tag, the
        DIE size must be at least sizeof (short) larger, otherwise they
        are forced to be TAG_padding DIES.

        Padding DIES must be at least sizeof(long) in length, implying that
        if a padding DIE is used for alignment and the amount needed is less
        than sizeof(long) then the padding DIE has to be big enough to align
        to the next alignment boundry.
 */

static void
basicdieinfo (dip, diep)
     struct dieinfo *dip;
     char *diep;
{
  curdie = dip;
  (void) memset (dip, 0, sizeof (struct dieinfo));
  dip -> die = diep;
  dip -> dieref = dbroff + (diep - dbbase);
  (void) memcpy (&dip -> dielength, diep, sizeof (long));
  if (dip -> dielength < sizeof (long))
    {
      dwarfwarn ("malformed DIE, bad length (%d bytes)", dip -> dielength);
    }
  else if (dip -> dielength < (sizeof (long) + sizeof (short)))
    {
      dip -> dietag = TAG_padding;
    }
  else
    {
      (void) memcpy (&dip -> dietag, diep + sizeof (long), sizeof (short));
    }
}

/*

LOCAL FUNCTION

        completedieinfo -- finish reading the information for a given DIE

SYNOPSIS

        void completedieinfo (struct dieinfo *dip)

DESCRIPTION

        Given a pointer to an already partially initialized die info structure,
        scan the raw DIE data and finish filling in the die info structure
        from the various attributes found.
   
        Note that since there is no guarantee that the data is properly
        aligned in memory for the type of access required (indirection
        through anything other than a char pointer), we use memcpy to
        shuffle data items larger than a char.  Possibly inefficient, but
        quite portable.

NOTES

        Each time we are called, we increment the diecount variable, which
        keeps an approximate count of the number of dies processed for
        each compilation unit.  This information is presented to the user
        if the info_verbose flag is set.

 */

static void
completedieinfo (dip)
     struct dieinfo *dip;
{
  char *diep;                   /* Current pointer into raw DIE data */
  char *end;                    /* Terminate DIE scan here */
  unsigned short attr;          /* Current attribute being scanned */
  unsigned short form;          /* Form of the attribute */
  short block2sz;               /* Size of a block2 attribute field */
  long block4sz;                /* Size of a block4 attribute field */
  
  diecount++;
  diep = dip -> die;
  end = diep + dip -> dielength;
  diep += sizeof (long) + sizeof (short);
  while (diep < end)
    {
      (void) memcpy (&attr, diep, sizeof (short));
      diep += sizeof (short);
      switch (attr)
        {
        case AT_fund_type:
          (void) memcpy (&dip -> at_fund_type, diep, sizeof (short));
          break;
        case AT_ordering:
          (void) memcpy (&dip -> at_ordering, diep, sizeof (short));
          break;
        case AT_bit_offset:
          (void) memcpy (&dip -> at_bit_offset, diep, sizeof (short));
          break;
        case AT_visibility:
          (void) memcpy (&dip -> at_visibility, diep, sizeof (short));
          break;
        case AT_sibling:
          (void) memcpy (&dip -> at_sibling, diep, sizeof (long));
          break;
        case AT_stmt_list:
          (void) memcpy (&dip -> at_stmt_list, diep, sizeof (long));
          dip -> has_at_stmt_list = 1;
          break;
        case AT_low_pc:
          (void) memcpy (&dip -> at_low_pc, diep, sizeof (long));
          dip -> at_low_pc += baseaddr;
          dip -> has_at_low_pc = 1;
          break;
        case AT_high_pc:
          (void) memcpy (&dip -> at_high_pc, diep, sizeof (long));
          dip -> at_high_pc += baseaddr;
          break;
        case AT_language:
          (void) memcpy (&dip -> at_language, diep, sizeof (long));
          break;
        case AT_user_def_type:
          (void) memcpy (&dip -> at_user_def_type, diep, sizeof (long));
          break;
        case AT_byte_size:
          (void) memcpy (&dip -> at_byte_size, diep, sizeof (long));
          break;
        case AT_bit_size:
          (void) memcpy (&dip -> at_bit_size, diep, sizeof (long));
          break;
        case AT_member:
          (void) memcpy (&dip -> at_member, diep, sizeof (long));
          break;
        case AT_discr:
          (void) memcpy (&dip -> at_discr, diep, sizeof (long));
          break;
        case AT_import:
          (void) memcpy (&dip -> at_import, diep, sizeof (long));
          break;
        case AT_location:
          dip -> at_location = diep;
          break;
        case AT_mod_fund_type:
          dip -> at_mod_fund_type = diep;
          break;
        case AT_subscr_data:
          dip -> at_subscr_data = diep;
          break;
        case AT_mod_u_d_type:
          dip -> at_mod_u_d_type = diep;
          break;
        case AT_element_list:
          dip -> at_element_list = diep;
          dip -> short_element_list = 0;
          break;
        case AT_short_element_list:
          dip -> at_element_list = diep;
          dip -> short_element_list = 1;
          break;
        case AT_discr_value:
          dip -> at_discr_value = diep;
          break;
        case AT_string_length:
          dip -> at_string_length = diep;
          break;
        case AT_name:
          dip -> at_name = diep;
          break;
        case AT_comp_dir:
          dip -> at_comp_dir = diep;
          break;
        case AT_producer:
          dip -> at_producer = diep;
          break;
        case AT_frame_base:
          (void) memcpy (&dip -> at_frame_base, diep, sizeof (long));
          break;
        case AT_start_scope:
          (void) memcpy (&dip -> at_start_scope, diep, sizeof (long));
          break;
        case AT_stride_size:
          (void) memcpy (&dip -> at_stride_size, diep, sizeof (long));
          break;
        case AT_src_info:
          (void) memcpy (&dip -> at_src_info, diep, sizeof (long));
          break;
        case AT_prototyped:
          (void) memcpy (&dip -> at_prototyped, diep, sizeof (short));
          break;
        default:
          /* Found an attribute that we are unprepared to handle.  However
             it is specifically one of the design goals of DWARF that
             consumers should ignore unknown attributes.  As long as the
             form is one that we recognize (so we know how to skip it),
             we can just ignore the unknown attribute. */
          break;
        }
      form = attr & 0xF;
      switch (form)
        {
        case FORM_DATA2:
          diep += sizeof (short);
          break;
        case FORM_DATA4:
          diep += sizeof (long);
          break;
        case FORM_DATA8:
          diep += 8 * sizeof (char);    /* sizeof (long long) ? */
          break;
        case FORM_ADDR:
        case FORM_REF:
          diep += sizeof (long);
          break;
        case FORM_BLOCK2:
          (void) memcpy (&block2sz, diep, sizeof (short));
          block2sz += sizeof (short);
          diep += block2sz;
          break;
        case FORM_BLOCK4:
          (void) memcpy (&block4sz, diep, sizeof (long));
          block4sz += sizeof (long);
          diep += block4sz;
          break;
        case FORM_STRING:
          diep += strlen (diep) + 1;
          break;
        default:
          SQUAWK (("unknown attribute form (0x%x), skipped rest", form));
          diep = end;
          break;
        }
    }
}