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Roland McGrath
182
libc-symbols.h
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182
libc-symbols.h
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/* Support macros for making weak and strong aliases for symbols,
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and for using symbol sets and linker warnings with GNU ld.
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Copyright (C) 1995 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#ifndef _LIBC_SYMBOLS_H
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#define _LIBC_SYMBOLS_H
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/* This file's macros are included implicitly in the compilation of every
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file in the C library by -imacros.
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We include config.h which is generated by configure.
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It should define for us the following symbols:
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* HAVE_GNU_LD if using GNU ld, with support for weak symbols in a.out,
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and for symbol set and warning messages extensions in a.out and ELF.
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This implies HAVE_WEAK_SYMBOLS; set by --with-gnu-ld.
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* HAVE_ELF if using ELF, which supports weak symbols.
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This implies HAVE_WEAK_SYMBOLS; set by --with-elf.
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* HAVE_WEAK_SYMBOLS if weak symbols are available in the assembler and
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linker being used. Set by --with-weak-symbols.
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*/
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#include <config.h>
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/* This is defined for the compilation of all C library code.
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features.h tests this to avoid inclusion of stubs.h while
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compiling the library, before stubs.h has been generated.
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Some library code that is shared with other packages also
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tests this symbol to see if it is being compiled as part
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of the C library. */
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#define _LIBC
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/* The symbols in all the user (non-_) macros are C symbols. Predefined
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should be HAVE_WEAK_SYMBOLS and/or HAVE_ELF and/or HAVE_GNU_LD.
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HAVE_WEAK_SYMBOLS is implied by the other two. HAVE_GNU_LD without
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HAVE_ELF implies a.out. */
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#ifndef HAVE_WEAK_SYMBOLS
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#if defined (HAVE_ELF) || defined (HAVE_GNU_LD)
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#define HAVE_WEAK_SYMBOLS
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#endif
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#endif
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#ifndef __SYMBOL_PREFIX
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#ifdef HAVE_ELF
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#define NO_UNDERSCORES
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#else
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#include <sysdep.h> /* Should define NO_UNDERSCORES. */
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#endif
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#ifdef NO_UNDERSCORES
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#define __SYMBOL_PREFIX
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#else
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#define __SYMBOL_PREFIX "_"
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#endif
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#endif
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#ifndef C_SYMBOL_NAME
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#ifdef NO_UNDERSCORES
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#define C_SYMBOL_NAME(name) name
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#else
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#define C_SYMBOL_NAME(name) _##name
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#endif
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#endif
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/* Define ALIAS as a strong alias for ORIGINAL. */
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#define strong_alias_asm(original, alias) \
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.set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
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#ifdef ASSEMBLER
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#define strong_alias(original, alias) strong_alias_asm (original, alias)
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#else
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#define strong_alias(original, alias) \
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asm (".set " __SYMBOL_PREFIX #alias "," __SYMBOL_PREFIX #original);
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#endif
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/* Define ALIAS as a weak alias for ORIGINAL.
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If weak aliases are not available, this defines a strong alias. */
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#ifdef HAVE_WEAK_SYMBOLS
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#ifdef ASSEMBLER
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#define weak_alias(original, alias) \
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.weak C_SYMBOL_NAME (alias); \
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C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
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#else
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#define weak_alias(original, alias) \
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asm (".weak " __SYMBOL_PREFIX #alias "\n" \
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__SYMBOL_PREFIX #alias " = " __SYMBOL_PREFIX #original);
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#endif
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#else
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#define weak_alias(original, alias) strong_alias(original, alias)
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#endif
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/* When the file using this macro is linked in, the linker
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will emit a warning message MSG. */
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#ifdef HAVE_GNU_LD
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#ifdef HAVE_ELF
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#define link_warning(msg) \
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static const char __evoke_link_warning__[] \
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__attribute__ ((section (".gnu.warning"))) = msg;
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#else
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#define link_warning(msg) \
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asm(".stabs \"" msg "\",30,0,0,0\n" \
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".stabs \"__evoke_link_warning__\",1,0,0,0\n"\
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".stabs \"__evoke_link_warning__\",2,0,0,0\n");
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#endif
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#else
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/* We will never be heard; they will all die horribly. */
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#define link_warning(msg)
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#endif
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/* A canned warning for sysdeps/stub functions. */
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#define stub_warning(name) \
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link_warning ("warning: " #name " is not implemented and will always fail")
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#ifdef HAVE_GNU_LD
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/* Symbol set support macros. */
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#ifdef HAVE_ELF
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/* Make SYMBOL, which is in the text segment, an element of SET. */
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#define text_set_element(set, symbol) _elf_set_element(set, symbol)
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/* Make SYMBOL, which is in the data segment, an element of SET. */
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#define data_set_element(set, symbol) _elf_set_element(set, symbol)
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/* Make SYMBOL, which is in the bss segment, an element of SET. */
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#define bss_set_element(set, symbol) _elf_set_element(set, symbol)
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/* These are all done the same way in ELF.
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There is a new section created for each set. */
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#define _elf_set_element(set, symbol) \
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static const void *const __elf_set_##set##_element_##symbol##__ \
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__attribute__ ((section (#set))) = &(symbol)
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/* Define SET as a symbol set. This may be required (it is in a.out) to
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be able to use the set's contents. */
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#define symbol_set_define(set) symbol_set_declare(set)
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/* Declare SET for use in this module, if defined in another module. */
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#define symbol_set_declare(set) \
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extern void *const __start_##set, *const __stop_##set;
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/* Return a pointer (void *const *) to the first element of SET. */
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#define symbol_set_first_element(set) (&__start_##set)
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/* Return true iff PTR (a void *const *) has been incremented
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past the last element in SET. */
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#define symbol_set_end_p(set, ptr) ((ptr) >= &__stop_##set)
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#else /* Not ELF: a.out. */
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#define text_set_element(set, symbol) \
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asm(".stabs \"" __SYMBOL_PREFIX #set "\",23,0,0," __SYMBOL_PREFIX #symbol)
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#define data_set_element(set, symbol) \
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asm(".stabs \"" __SYMBOL_PREFIX #set "\",25,0,0," __SYMBOL_PREFIX #symbol)
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#define bss_set_element(set, symbol) ?error Must use initialized data.
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#define symbol_set_define(set) void *const (set)[1];
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#define symbol_set_declare(set) extern void *const (set)[1];
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#define symbol_set_first_element(set) &(set)[1]
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#define symbol_set_end_p(set, ptr) (*(ptr) == 0)
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#endif /* ELF. */
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#endif /* Have GNU ld. */
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#endif /* libc-symbols.h */
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