gcc/crtstuff.c

   1 /* Specialized bits of code needed to support construction and
   2    destruction of file-scope objects in C++ code.
   3    Copyright (C) 1991, 1994, 1995, 1996, 1997, 1998,
   4    1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   5    Contributed by Ron Guilmette (rfg@monkeys.com).
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify it under
  10 the terms of the GNU General Public License as published by the Free
  11 Software Foundation; either version 2, or (at your option) any later
  12 version.
  13
  14 In addition to the permissions in the GNU General Public License, the
  15 Free Software Foundation gives you unlimited permission to link the
  16 compiled version of this file into combinations with other programs,
  17 and to distribute those combinations without any restriction coming
  18 from the use of this file.  (The General Public License restrictions
  19 do apply in other respects; for example, they cover modification of
  20 the file, and distribution when not linked into a combine
  21 executable.)
  22
  23 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  24 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  25 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  26 for more details.
  27
  28 You should have received a copy of the GNU General Public License
  29 along with GCC; see the file COPYING.  If not, write to the Free
  30 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  31 02111-1307, USA.  */
  32
  33 /* This file is a bit like libgcc2.c in that it is compiled
  34    multiple times and yields multiple .o files.
  35
  36    This file is useful on target machines where the object file format
  37    supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE).  On
  38    such systems, this file allows us to avoid running collect (or any
  39    other such slow and painful kludge).  Additionally, if the target
  40    system supports a .init section, this file allows us to support the
  41    linking of C++ code with a non-C++ main program.
  42
  43    Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
  44    this file *will* make use of the .init section.  If that symbol is
  45    not defined however, then the .init section will not be used.
  46
  47    Currently, only ELF and COFF are supported.  It is likely however that
  48    ROSE could also be supported, if someone was willing to do the work to
  49    make whatever (small?) adaptations are needed.  (Some work may be
  50    needed on the ROSE assembler and linker also.)
  51
  52    This file must be compiled with gcc.  */
  53
  54 /* It is incorrect to include config.h here, because this file is being
  55    compiled for the target, and hence definitions concerning only the host
  56    do not apply.  */
  57
  58 /* We include auto-host.h here to get HAVE_GAS_HIDDEN.  This is
  59    supposedly valid even though this is a "target" file.  */
  60 #include "auto-host.h"
  61 #include "tconfig.h"
  62 #include "tsystem.h"
  63 #include "coretypes.h"
  64 #include "tm.h"
  65 #include "unwind-dw2-fde.h"
  66
  67 #ifndef FORCE_CODE_SECTION_ALIGN
  68 # define FORCE_CODE_SECTION_ALIGN
  69 #endif
  70
  71 #ifndef CRT_CALL_STATIC_FUNCTION
  72 # define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC)     \
  73 static void __attribute__((__used__))                   \
  74 call_ ## FUNC (void)                                    \
  75 {                                                       \
  76   asm (SECTION_OP);                                     \
  77   FUNC ();                                              \
  78   FORCE_CODE_SECTION_ALIGN                              \
  79   asm (TEXT_SECTION_ASM_OP);                            \
  80 }
  81 #endif
  82
  83 #if defined(OBJECT_FORMAT_ELF) && defined(HAVE_LD_EH_FRAME_HDR) \
  84     && !defined(inhibit_libc) && !defined(CRTSTUFFT_O) \
  85     && defined(__GLIBC__) && __GLIBC__ >= 2
  86 #include <link.h>
  87 # if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
  88      || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
  89 #  define USE_PT_GNU_EH_FRAME
  90 # endif
  91 #endif
  92 #if defined(EH_FRAME_SECTION_NAME) && !defined(USE_PT_GNU_EH_FRAME)
  93 # define USE_EH_FRAME_REGISTRY
  94 #endif
  95 #if defined(EH_FRAME_SECTION_NAME) && defined(HAVE_LD_RO_RW_SECTION_MIXING)
  96 # define EH_FRAME_SECTION_CONST const
  97 #else
  98 # define EH_FRAME_SECTION_CONST
  99 #endif
 100
 101 /* We do not want to add the weak attribute to the declarations of these
 102    routines in unwind-dw2-fde.h because that will cause the definition of
 103    these symbols to be weak as well.
 104
 105    This exposes a core issue, how to handle creating weak references vs
 106    how to create weak definitions.  Either we have to have the definition
 107    of TARGET_WEAK_ATTRIBUTE be conditional in the shared header files or
 108    have a second declaration if we want a function's references to be weak,
 109    but not its definition.
 110
 111    Making TARGET_WEAK_ATTRIBUTE conditional seems like a good solution until
 112    one thinks about scaling to larger problems -- ie, the condition under
 113    which TARGET_WEAK_ATTRIBUTE is active will eventually get far too
 114    complicated.
 115
 116    So, we take an approach similar to #pragma weak -- we have a second
 117    declaration for functions that we want to have weak references.
 118
 119    Neither way is particularly good.  */
 120
 121 /* References to __register_frame_info and __deregister_frame_info should
 122    be weak in this file if at all possible.  */
 123 extern void __register_frame_info (const void *, struct object *)
 124                                   TARGET_ATTRIBUTE_WEAK;
 125 extern void __register_frame_info_bases (const void *, struct object *,
 126                                          void *, void *)
 127                                   TARGET_ATTRIBUTE_WEAK;
 128 extern void *__deregister_frame_info (const void *)
 129                                      TARGET_ATTRIBUTE_WEAK;
 130 extern void *__deregister_frame_info_bases (const void *)
 131                                      TARGET_ATTRIBUTE_WEAK;
 132 extern void __do_global_ctors_1 (void);
 133
 134 /* Likewise for _Jv_RegisterClasses.  */
 135 extern void _Jv_RegisterClasses (void *) TARGET_ATTRIBUTE_WEAK;
 136
 137 #ifdef OBJECT_FORMAT_ELF
 138
 139 /*  Declare a pointer to void function type.  */
 140 typedef void (*func_ptr) (void);
 141 #define STATIC static
 142
 143 #else  /* OBJECT_FORMAT_ELF */
 144
 145 #include "gbl-ctors.h"
 146
 147 #define STATIC
 148
 149 #endif /* OBJECT_FORMAT_ELF */
 150
 151 #ifdef CRT_BEGIN
 152
 153 /* NOTE:  In order to be able to support SVR4 shared libraries, we arrange
 154    to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__,
 155    __DTOR_END__ } per root executable and also one set of these symbols
 156    per shared library.  So in any given whole process image, we may have
 157    multiple definitions of each of these symbols.  In order to prevent
 158    these definitions from conflicting with one another, and in order to
 159    ensure that the proper lists are used for the initialization/finalization
 160    of each individual shared library (respectively), we give these symbols
 161    only internal (i.e. `static') linkage, and we also make it a point to
 162    refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__
 163    symbol in crtbegin.o, where they are defined.  */
 164
 165 /* The -1 is a flag to __do_global_[cd]tors indicating that this table
 166    does not start with a count of elements.  */
 167 #ifdef CTOR_LIST_BEGIN
 168 CTOR_LIST_BEGIN;
 169 #elif defined(CTORS_SECTION_ASM_OP)
 170 /* Hack: force cc1 to switch to .data section early, so that assembling
 171    __CTOR_LIST__ does not undo our behind-the-back change to .ctors.  */
 172 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
 173 asm (CTORS_SECTION_ASM_OP);
 174 STATIC func_ptr __CTOR_LIST__[1]
 175   __attribute__ ((__unused__, aligned(sizeof(func_ptr))))
 176   = { (func_ptr) (-1) };
 177 #else
 178 STATIC func_ptr __CTOR_LIST__[1]
 179   __attribute__ ((__unused__, section(".ctors"), aligned(sizeof(func_ptr))))
 180   = { (func_ptr) (-1) };
 181 #endif /* __CTOR_LIST__ alternatives */
 182
 183 #ifdef DTOR_LIST_BEGIN
 184 DTOR_LIST_BEGIN;
 185 #elif defined(DTORS_SECTION_ASM_OP)
 186 asm (DTORS_SECTION_ASM_OP);
 187 STATIC func_ptr __DTOR_LIST__[1]
 188   __attribute__ ((aligned(sizeof(func_ptr))))
 189   = { (func_ptr) (-1) };
 190 #else
 191 STATIC func_ptr __DTOR_LIST__[1]
 192   __attribute__((section(".dtors"), aligned(sizeof(func_ptr))))
 193   = { (func_ptr) (-1) };
 194 #endif /* __DTOR_LIST__ alternatives */
 195
 196 #ifdef USE_EH_FRAME_REGISTRY
 197 /* Stick a label at the beginning of the frame unwind info so we can register
 198    and deregister it with the exception handling library code.  */
 199 STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
 200      __attribute__((section(EH_FRAME_SECTION_NAME), aligned(4)))
 201      = { };
 202 #endif /* USE_EH_FRAME_REGISTRY */
 203
 204 #ifdef JCR_SECTION_NAME
 205 /* Stick a label at the beginning of the java class registration info
 206    so we can register them properly.  */
 207 STATIC void *__JCR_LIST__[]
 208   __attribute__ ((unused, section(JCR_SECTION_NAME), aligned(sizeof(void*))))
 209   = { };
 210 #endif /* JCR_SECTION_NAME */
 211
 212 #ifdef INIT_SECTION_ASM_OP
 213
 214 #ifdef OBJECT_FORMAT_ELF
 215
 216 /* Declare the __dso_handle variable.  It should have a unique value
 217    in every shared-object; in a main program its value is zero.  The
 218    object should in any case be protected.  This means the instance
 219    in one DSO or the main program is not used in another object.  The
 220    dynamic linker takes care of this.  */
 221
 222 #ifdef HAVE_GAS_HIDDEN
 223 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
 224 #endif
 225 #ifdef CRTSTUFFS_O
 226 void *__dso_handle = &__dso_handle;
 227 #else
 228 void *__dso_handle = 0;
 229 #endif
 230
 231 /* The __cxa_finalize function may not be available so we use only a
 232    weak declaration.  */
 233 extern void __cxa_finalize (void *) TARGET_ATTRIBUTE_WEAK;
 234
 235 /* Run all the global destructors on exit from the program.  */
 236
 237 /* Some systems place the number of pointers in the first word of the
 238    table.  On SVR4 however, that word is -1.  In all cases, the table is
 239    null-terminated.  On SVR4, we start from the beginning of the list and
 240    invoke each per-compilation-unit destructor routine in order
 241    until we find that null.
 242
 243    Note that this function MUST be static.  There will be one of these
 244    functions in each root executable and one in each shared library, but
 245    although they all have the same code, each one is unique in that it
 246    refers to one particular associated `__DTOR_LIST__' which belongs to the
 247    same particular root executable or shared library file.
 248
 249    On some systems, this routine is run more than once from the .fini,
 250    when exit is called recursively, so we arrange to remember where in
 251    the list we left off processing, and we resume at that point,
 252    should we be re-invoked.  */
 253
 254 static void __attribute__((used))
 255 __do_global_dtors_aux (void)
 256 {
 257   static func_ptr *p = __DTOR_LIST__ + 1;
 258   static _Bool completed;
 259   func_ptr f;
 260
 261   if (__builtin_expect (completed, 0))
 262     return;
 263
 264 #ifdef CRTSTUFFS_O
 265   if (__cxa_finalize)
 266     __cxa_finalize (__dso_handle);
 267 #endif
 268
 269   while ((f = *p))
 270     {
 271       p++;
 272       f ();
 273     }
 274
 275 #ifdef USE_EH_FRAME_REGISTRY
 276 #ifdef CRT_GET_RFIB_DATA
 277   /* If we used the new __register_frame_info_bases interface,
 278      make sure that we deregister from the same place.  */
 279   if (__deregister_frame_info_bases)
 280     __deregister_frame_info_bases (__EH_FRAME_BEGIN__);
 281 #else
 282   if (__deregister_frame_info)
 283     __deregister_frame_info (__EH_FRAME_BEGIN__);
 284 #endif
 285 #endif
 286
 287   completed = 1;
 288 }
 289
 290 /* Stick a call to __do_global_dtors_aux into the .fini section.  */
 291 CRT_CALL_STATIC_FUNCTION (FINI_SECTION_ASM_OP, __do_global_dtors_aux)
 292
 293 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
 294 /* Stick a call to __register_frame_info into the .init section.  For some
 295    reason calls with no arguments work more reliably in .init, so stick the
 296    call in another function.  */
 297
 298 static void __attribute__((used))
 299 frame_dummy (void)
 300 {
 301 #ifdef USE_EH_FRAME_REGISTRY
 302   static struct object object;
 303 #ifdef CRT_GET_RFIB_DATA
 304   void *tbase, *dbase;
 305   tbase = 0;
 306   CRT_GET_RFIB_DATA (dbase);
 307   if (__register_frame_info_bases)
 308     __register_frame_info_bases (__EH_FRAME_BEGIN__, &object, tbase, dbase);
 309 #else
 310   if (__register_frame_info)
 311     __register_frame_info (__EH_FRAME_BEGIN__, &object);
 312 #endif /* CRT_GET_RFIB_DATA */
 313 #endif /* USE_EH_FRAME_REGISTRY */
 314 #ifdef JCR_SECTION_NAME
 315   if (__JCR_LIST__[0] && _Jv_RegisterClasses)
 316     _Jv_RegisterClasses (__JCR_LIST__);
 317 #endif /* JCR_SECTION_NAME */
 318 }
 319
 320 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, frame_dummy)
 321 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
 322
 323 #else  /* OBJECT_FORMAT_ELF */
 324
 325 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
 326    and once in crtend.o).  It must be declared static to avoid a link
 327    error.  Here, we define __do_global_ctors as an externally callable
 328    function.  It is externally callable so that __main can invoke it when
 329    INVOKE__main is defined.  This has the additional effect of forcing cc1
 330    to switch to the .text section.  */
 331
 332 static void __do_global_ctors_aux (void);
 333 void
 334 __do_global_ctors (void)
 335 {
 336 #ifdef INVOKE__main
 337   /* If __main won't actually call __do_global_ctors then it doesn't matter
 338      what's inside the function.  The inside of __do_global_ctors_aux is
 339      called automatically in that case.  And the Alliant fx2800 linker
 340      crashes on this reference.  So prevent the crash.  */
 341   __do_global_ctors_aux ();
 342 #endif
 343 }
 344
 345 asm (INIT_SECTION_ASM_OP);      /* cc1 doesn't know that we are switching! */
 346
 347 /* A routine to invoke all of the global constructors upon entry to the
 348    program.  We put this into the .init section (for systems that have
 349    such a thing) so that we can properly perform the construction of
 350    file-scope static-storage C++ objects within shared libraries.  */
 351
 352 static void __attribute__((used))
 353 __do_global_ctors_aux (void)    /* prologue goes in .init section */
 354 {
 355   FORCE_CODE_SECTION_ALIGN      /* explicit align before switch to .text */
 356   asm (TEXT_SECTION_ASM_OP);    /* don't put epilogue and body in .init */
 357   DO_GLOBAL_CTORS_BODY;
 358   atexit (__do_global_dtors);
 359 }
 360
 361 #endif /* OBJECT_FORMAT_ELF */
 362
 363 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
 364
 365 /* This case is used by the Irix 6 port, which supports named sections but
 366    not an SVR4-style .fini section.  __do_global_dtors can be non-static
 367    in this case because we protect it with -hidden_symbol.  */
 368
 369 void
 370 __do_global_dtors (void)
 371 {
 372   func_ptr *p, f;
 373   for (p = __DTOR_LIST__ + 1; (f = *p); p++)
 374     f ();
 375
 376 #ifdef USE_EH_FRAME_REGISTRY
 377   if (__deregister_frame_info)
 378     __deregister_frame_info (__EH_FRAME_BEGIN__);
 379 #endif
 380 }
 381
 382 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
 383 /* A helper function for __do_global_ctors, which is in crtend.o.  Here
 384    in crtbegin.o, we can reference a couple of symbols not visible there.
 385    Plus, since we're before libgcc.a, we have no problems referencing
 386    functions from there.  */
 387 void
 388 __do_global_ctors_1(void)
 389 {
 390 #ifdef USE_EH_FRAME_REGISTRY
 391   static struct object object;
 392   if (__register_frame_info)
 393     __register_frame_info (__EH_FRAME_BEGIN__, &object);
 394 #endif
 395 #ifdef JCR_SECTION_NAME
 396   if (__JCR_LIST__[0] && _Jv_RegisterClasses)
 397     _Jv_RegisterClasses (__JCR_LIST__);
 398 #endif
 399 }
 400 #endif /* USE_EH_FRAME_REGISTRY || JCR_SECTION_NAME */
 401
 402 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
 403 #error "What are you doing with crtstuff.c, then?"
 404 #endif
 405
 406 #elif defined(CRT_END) /* ! CRT_BEGIN */
 407
 408 /* Put a word containing zero at the end of each of our two lists of function
 409    addresses.  Note that the words defined here go into the .ctors and .dtors
 410    sections of the crtend.o file, and since that file is always linked in
 411    last, these words naturally end up at the very ends of the two lists
 412    contained in these two sections.  */
 413
 414 #ifdef CTOR_LIST_END
 415 CTOR_LIST_END;
 416 #elif defined(CTORS_SECTION_ASM_OP)
 417 /* Hack: force cc1 to switch to .data section early, so that assembling
 418    __CTOR_LIST__ does not undo our behind-the-back change to .ctors.  */
 419 static func_ptr force_to_data[1] __attribute__ ((__unused__)) = { };
 420 asm (CTORS_SECTION_ASM_OP);
 421 STATIC func_ptr __CTOR_END__[1]
 422   __attribute__((aligned(sizeof(func_ptr))))
 423   = { (func_ptr) 0 };
 424 #else
 425 STATIC func_ptr __CTOR_END__[1]
 426   __attribute__((section(".ctors"), aligned(sizeof(func_ptr))))
 427   = { (func_ptr) 0 };
 428 #endif
 429
 430 #ifdef DTOR_LIST_END
 431 DTOR_LIST_END;
 432 #elif defined(DTORS_SECTION_ASM_OP)
 433 asm (DTORS_SECTION_ASM_OP);
 434 STATIC func_ptr __DTOR_END__[1]
 435   __attribute__ ((unused, aligned(sizeof(func_ptr))))
 436   = { (func_ptr) 0 };
 437 #else
 438 STATIC func_ptr __DTOR_END__[1]
 439   __attribute__((unused, section(".dtors"), aligned(sizeof(func_ptr))))
 440   = { (func_ptr) 0 };
 441 #endif
 442
 443 #ifdef EH_FRAME_SECTION_NAME
 444 /* Terminate the frame unwind info section with a 4byte 0 as a sentinel;
 445    this would be the 'length' field in a real FDE.  */
 446 STATIC EH_FRAME_SECTION_CONST int __FRAME_END__[]
 447      __attribute__ ((unused, mode(SI), section(EH_FRAME_SECTION_NAME),
 448                      aligned(4)))
 449      = { 0 };
 450 #endif /* EH_FRAME_SECTION_NAME */
 451
 452 #ifdef JCR_SECTION_NAME
 453 /* Null terminate the .jcr section array.  */
 454 STATIC void *__JCR_END__[1]
 455    __attribute__ ((unused, section(JCR_SECTION_NAME),
 456                    aligned(sizeof(void *))))
 457    = { 0 };
 458 #endif /* JCR_SECTION_NAME */
 459
 460 #ifdef INIT_SECTION_ASM_OP
 461
 462 #ifdef OBJECT_FORMAT_ELF
 463 static void __attribute__((used))
 464 __do_global_ctors_aux (void)
 465 {
 466   func_ptr *p;
 467   for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
 468     (*p) ();
 469 }
 470
 471 /* Stick a call to __do_global_ctors_aux into the .init section.  */
 472 CRT_CALL_STATIC_FUNCTION (INIT_SECTION_ASM_OP, __do_global_ctors_aux)
 473 #else  /* OBJECT_FORMAT_ELF */
 474
 475 /* Stick the real initialization code, followed by a normal sort of
 476    function epilogue at the very end of the .init section for this
 477    entire root executable file or for this entire shared library file.
 478
 479    Note that we use some tricks here to get *just* the body and just
 480    a function epilogue (but no function prologue) into the .init
 481    section of the crtend.o file.  Specifically, we switch to the .text
 482    section, start to define a function, and then we switch to the .init
 483    section just before the body code.
 484
 485    Earlier on, we put the corresponding function prologue into the .init
 486    section of the crtbegin.o file (which will be linked in first).
 487
 488    Note that we want to invoke all constructors for C++ file-scope static-
 489    storage objects AFTER any other possible initialization actions which
 490    may be performed by the code in the .init section contributions made by
 491    other libraries, etc.  That's because those other initializations may
 492    include setup operations for very primitive things (e.g. initializing
 493    the state of the floating-point coprocessor, etc.) which should be done
 494    before we start to execute any of the user's code.  */
 495
 496 static void
 497 __do_global_ctors_aux (void)    /* prologue goes in .text section */
 498 {
 499   asm (INIT_SECTION_ASM_OP);
 500   DO_GLOBAL_CTORS_BODY;
 501   atexit (__do_global_dtors);
 502 }                               /* epilogue and body go in .init section */
 503
 504 FORCE_CODE_SECTION_ALIGN
 505 asm (TEXT_SECTION_ASM_OP);
 506
 507 #endif /* OBJECT_FORMAT_ELF */
 508
 509 #elif defined(HAS_INIT_SECTION) /* ! INIT_SECTION_ASM_OP */
 510
 511 /* This case is used by the Irix 6 port, which supports named sections but
 512    not an SVR4-style .init section.  __do_global_ctors can be non-static
 513    in this case because we protect it with -hidden_symbol.  */
 514 void
 515 __do_global_ctors (void)
 516 {
 517   func_ptr *p;
 518 #if defined(USE_EH_FRAME_REGISTRY) || defined(JCR_SECTION_NAME)
 519   __do_global_ctors_1();
 520 #endif
 521   for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
 522     (*p) ();
 523 }
 524
 525 #else /* ! INIT_SECTION_ASM_OP && ! HAS_INIT_SECTION */
 526 #error "What are you doing with crtstuff.c, then?"
 527 #endif
 528
 529 #else /* ! CRT_BEGIN && ! CRT_END */
 530 #error "One of CRT_BEGIN or CRT_END must be defined."
 531 #endif