+2001-09-12 Paul Sokolovsky <Paul.Sokolovsky@technologist.com>
+
+ * emultempl/pe.em(make_import_fixup): change signature to
+ take asection as well as arelec; we need this for proper
+ error reporting. Only call pe_create_import_fixup() if
+ there is no attempt to add a constant addend to the reloc;
+ otherwise, report error condition.
+ * pe-dll.c(pe_walk_relocs_of_symbol): change signature,
+ since final argument is a pointer to make_import_fixup().
+ Change call to cb() to match make_import_fixup() signature.
+ (make_import_fixup_mark): make buffer_len unsigned.
+ * pe-dll.h: change signature of pe_walk_relocs_of_symbol.
+
+2001-09-12 Charles Wilson <cwilson@ece.gatech.edu>
+
+ * ld.texinfo: add verbose documentation for auto-import
+ direct-addressing workaround, to compliment the terse
+ error message.
+
2001-09-12 Andrew MacLeod <amacleod@redhat.com>
* scripttempl/v850.sc: Add gcc_except_table sections.
static boolean pe_undef_cdecl_match
PARAMS ((struct bfd_link_hash_entry *, PTR));
static void pe_fixup_stdcalls PARAMS ((void));
-static int make_import_fixup PARAMS ((arelent *));
+static int make_import_fixup PARAMS ((arelent *, asection *));
static void pe_find_data_imports PARAMS ((void));
#endif
}
static int
-make_import_fixup (rel)
+make_import_fixup (rel, s)
arelent *rel;
+ asection *s;
{
struct symbol_cache_entry *sym = *rel->sym_ptr_ptr;
-/*
- bfd *b;
-*/
if (pe_dll_extra_pe_debug)
{
printf ("arelent: %s@%#x: add=%li\n", sym->name,
(int) rel->address, rel->addend);
}
- pe_create_import_fixup (rel);
+
+ {
+ int addend = 0;
+ if (!bfd_get_section_contents(s->owner, s, &addend, rel->address, sizeof(addend)))
+ {
+ einfo (_("%C: Cannot get section contents - auto-import exception\n"),
+ s->owner, s, rel->address);
+ }
+
+ if (addend == 0)
+ pe_create_import_fixup (rel);
+ else
+ {
+ einfo (_("%C: variable '%T' can't be auto-imported. Please read the documentation for ld's --enable-auto-import for details.\n"),
+ s->owner, s, rel->address, sym->name);
+ einfo ("%X");
+ }
+ }
+
return 1;
}
@kindex --enable-auto-import
@item --enable-auto-import
-Do sophisticalted linking of @code{_symbol} to @code{__imp__symbol} for
+Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for
DATA imports from DLLs, and create the necessary thunking symbols when
-building the DLLs with those DATA exports.
+building the DLLs with those DATA exports. This generally will 'just
+work' -- but sometimes you may see this message:
+
+"variable '<var>' can't be auto-imported. Please read the
+documentation for ld's @code{--enable-auto-import} for details."
+
+This message occurs when some (sub)expression accesses an address
+ultimately given by the sum of two constants (Win32 import tables only
+allow one). Instances where this may occur include accesses to member
+fields of struct variables imported from a DLL, as well as using a
+constant index into an array variable imported from a DLL. There are
+several ways to address this difficulty.
+
+One solution is to force one of the 'constants' to be a variable --
+that is, unknown and un-optimizable at compile time. For arrays,
+there are two possibilities: a) make the indexee (the array's address)
+a variable, or b) make the 'constant' index a variable. Thus:
+
+@example
+extern type extern_array[];
+extern_array[1] -->
+ @{ volatile type *t=extern_array; t[1] @}
+@end example
+
+or
+
+@example
+extern type extern_array[];
+extern_array[1] -->
+ @{ volatile int t=1; extern_array[t] @}
+@end example
+
+For structs, the only option is to make the struct itself variable:
+
+@example
+extern struct s extern_struct;
+extern_struct.field -->
+ @{ volatile struct s *t=&extern_struct; t->field @}
+@end example
+
+A second method of dealing with this difficulty is to abandon
+'auto-import' for the offending symbol and mark it with
+@code{__declspec(dllimport)}. However, in practice that
+requires using compile-time #defines to indicate whether you are
+building a DLL, building client code that will link to the DLL, or
+merely building/linking to a static library. In making the choice
+between the various methods of resolving the 'direct address with
+constant offset' problem, you should consider typical real-world usage:
+
+Original:
+@example
+--foo.h
+extern int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ printf("%d\n",arr[1]);
+@}
+@end example
+
+Solution 1:
+@example
+--foo.h
+extern int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ /* This workaround is for win32 and cygwin; do not "optimize" */
+ volatile int *parr = arr;
+ printf("%d\n",parr[1]);
+@}
+@end example
+
+Solution 2:
+@example
+--foo.h
+/* Note: auto-export is assumed (no __declspec(dllexport)) */
+#if (defined(_WIN32) || defined(__CYGWIN__)) && \
+ !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
+#define FOO_IMPORT __declspec(dllimport)
+#else
+#define FOO_IMPORT
+#endif
+extern FOO_IMPORT int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ printf("%d\n",arr[1]);
+@}
+@end example
+
+A third way to avoid this problem is to re-code your
+library to use a functional interface rather than a data interface
+for the offending variables (e.g. set_foo() and get_foo() accessor
+functions).
@kindex --disable-auto-import
@item --disable-auto-import
pe_walk_relocs_of_symbol (info, name, cb)
struct bfd_link_info *info;
CONST char *name;
- int (*cb) (arelent *);
+ int (*cb) (arelent *, asection *);
{
bfd *b;
- struct sec *s;
+ asection *s;
for (b = info->input_bfds; b; b = b->link_next)
{
&& s->output_section == bfd_abs_section_ptr)
continue;
- current_sec=s;
+ current_sec = s;
symsize = bfd_get_symtab_upper_bound (b);
symbols = (asymbol **) xmalloc (symsize);
for (i = 0; i < nrelocs; i++)
{
struct symbol_cache_entry *sym = *relocs[i]->sym_ptr_ptr;
- if (!strcmp(name,sym->name)) cb(relocs[i]);
+ if (!strcmp(name,sym->name)) cb(relocs[i], s);
}
free (relocs);
/* Warning: the allocated symbols are remembered in BFD and reused
/* we convert reloc to symbol, for later reference */
static int counter;
static char *fixup_name = NULL;
- static int buffer_len = 0;
+ static unsigned int buffer_len = 0;
struct symbol_cache_entry *sym = *rel->sym_ptr_ptr;
extern void pe_walk_relocs_of_symbol PARAMS ((struct bfd_link_info * info,
CONST char *name,
- int (*cb) (arelent *)));
+ int (*cb) (arelent *, asection *)));
extern void pe_create_import_fixup PARAMS ((arelent * rel));
#endif /* PE_DLL_H */
projects / binutils-gdb.git / commitdiff