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353 lines
13 KiB
C
353 lines
13 KiB
C
/* 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) 1995,1996,1997,1998,2000,2001 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 Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#ifndef _LIBC_SYMBOLS_H
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#define _LIBC_SYMBOLS_H 1
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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_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'.
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* ASM_GLOBAL_DIRECTIVE with `.globl' or `.global'.
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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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* HAVE_ELF if using ELF, which supports weak symbols using `.weak'.
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* HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'.
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* HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'.
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*/
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/* This is defined for the compilation of all C library code. features.h
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tests this to avoid inclusion of stubs.h while compiling the library,
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before stubs.h has been generated. Some library code that is shared
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with other packages also tests this symbol to see if it is being
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compiled as part of the C library. We must define this before including
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config.h, because it makes some definitions conditional on whether libc
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itself is being compiled, or just some generator program. */
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#define _LIBC 1
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/* Enable declarations of GNU extensions, since we are compiling them. */
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#define _GNU_SOURCE 1
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/* And we also need the data for the reentrant functions. */
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#define _REENTRANT 1
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#include <config.h>
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/* The symbols in all the user (non-_) macros are C symbols.
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HAVE_GNU_LD without HAVE_ELF implies a.out. */
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#if defined HAVE_ASM_WEAK_DIRECTIVE || defined HAVE_ASM_WEAKEXT_DIRECTIVE
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# define HAVE_WEAK_SYMBOLS
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#endif
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#ifndef __SYMBOL_PREFIX
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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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#ifndef ASM_LINE_SEP
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# define ASM_LINE_SEP ;
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#endif
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#ifndef C_SYMBOL_DOT_NAME
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# define C_SYMBOL_DOT_NAME(name) .##name
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#endif
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#ifndef __ASSEMBLER__
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/* GCC understands weak symbols and aliases; use its interface where
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possible, instead of embedded assembly language. */
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/* Define ALIASNAME as a strong alias for NAME. */
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# define strong_alias(name, aliasname) _strong_alias(name, aliasname)
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# define _strong_alias(name, aliasname) \
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extern __typeof (name) aliasname __attribute__ ((__alias__ (#name)));
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/* This comes between the return type and function name in
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a function definition to make that definition weak. */
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# define weak_function __attribute__ ((__weak__))
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# define weak_const_function __attribute__ ((__weak__, __const__))
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# ifdef HAVE_WEAK_SYMBOLS
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/* Define ALIASNAME as a weak alias for NAME.
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If weak aliases are not available, this defines a strong alias. */
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# define weak_alias(name, aliasname) _weak_alias (name, aliasname)
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# define _weak_alias(name, aliasname) \
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extern __typeof (name) aliasname __attribute__ ((__weak__, __alias__ (#name)));
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/* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */
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# define weak_extern(symbol) _weak_extern (symbol)
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# ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
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# define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol);
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# else
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# define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol);
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# endif
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# else
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# define weak_alias(name, aliasname) strong_alias(name, aliasname)
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# define weak_extern(symbol) /* Nothing. */
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# endif
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#else /* __ASSEMBLER__ */
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# ifdef HAVE_ASM_SET_DIRECTIVE
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# define strong_alias(original, alias) \
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ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \
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.set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
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# else
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# ifdef HAVE_ASM_GLOBAL_DOT_NAME
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# define strong_alias(original, alias) \
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ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \
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ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
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# else
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# define strong_alias(original, alias) \
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ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
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# endif
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# endif
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# ifdef HAVE_WEAK_SYMBOLS
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# ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
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# define weak_alias(original, alias) \
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.weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
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# define weak_extern(symbol) \
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.weakext C_SYMBOL_NAME (symbol)
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# else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
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# ifdef HAVE_ASM_GLOBAL_DOT_NAME
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# define weak_alias(original, alias) \
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.weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \
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ASM_GLOBAL_DIRECTIVE C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
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# else
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# define weak_alias(original, alias) \
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.weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
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C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
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# endif
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# define weak_extern(symbol) \
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.weak C_SYMBOL_NAME (symbol)
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# endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
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# else /* ! HAVE_WEAK_SYMBOLS */
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# define weak_alias(original, alias) strong_alias(original, alias)
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# define weak_extern(symbol) /* Nothing */
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# endif /* ! HAVE_WEAK_SYMBOLS */
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#endif /* __ASSEMBLER__ */
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/* On some platforms we can make internal function calls (i.e., calls of
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functions not exported) a bit faster by using a different calling
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convention. */
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#ifndef internal_function
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# define internal_function /* empty */
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#endif
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/* Prepare for the case that `__builtin_expect' is not available. */
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#ifndef HAVE_BUILTIN_EXPECT
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# define __builtin_expect(expr, val) (expr)
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#endif
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/* Determine the return address. */
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#define RETURN_ADDRESS(nr) \
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__builtin_extract_return_addr (__builtin_return_address (nr))
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/* When a reference to SYMBOL is encountered, the linker will emit a
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warning message MSG. */
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#ifdef HAVE_GNU_LD
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# ifdef HAVE_ELF
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/* We want the .gnu.warning.SYMBOL section to be unallocated. */
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# ifdef HAVE_ASM_PREVIOUS_DIRECTIVE
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# define __make_section_unallocated(section_string) \
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asm (".section " section_string "\n\t.previous");
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# elif defined HAVE_ASM_POPSECTION_DIRECTIVE
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# define __make_section_unallocated(section_string) \
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asm (".pushsection " section_string "\n\t.popsection");
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# else
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# define __make_section_unallocated(section_string)
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# endif
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/* Tacking on "\n\t#" to the section name makes gcc put it's bogus
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section attributes on what looks like a comment to the assembler. */
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# ifdef HAVE_SECTION_QUOTES
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# define link_warning(symbol, msg) \
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__make_section_unallocated (".gnu.warning." #symbol) \
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static const char __evoke_link_warning_##symbol[] \
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__attribute__ ((__section__ (".gnu.warning." #symbol "\"\n\t#\""))) = msg;
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# else
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# define link_warning(symbol, msg) \
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__make_section_unallocated (".gnu.warning." #symbol) \
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static const char __evoke_link_warning_##symbol[] \
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__attribute__ ((__section__ (".gnu.warning." #symbol "\n\t#"))) = msg;
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# endif
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# else /* Not ELF: a.out */
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# ifdef HAVE_XCOFF
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/* XCOFF does not support .stabs.
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The native aix linker will remove the .stab and .stabstr sections
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The gnu linker will have a fatal error if there is a relocation for
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symbol in the .stab section. Silently disable this macro. */
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# define link_warning(symbol, msg)
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# else
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# define link_warning(symbol, msg) \
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asm (".stabs \"" msg "\",30,0,0,0\n\t" \
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".stabs \"" __SYMBOL_PREFIX #symbol "\",1,0,0,0\n");
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# endif /* XCOFF */
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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(symbol, 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 (name, \
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"warning: " #name " is not implemented and will always fail")
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/*
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*/
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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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# ifdef SHARED
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/* When building a shared library, make the set section writable,
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because it will need to be relocated at run time anyway. */
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# define _elf_set_element(set, symbol) \
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static const void *__elf_set_##set##_element_##symbol##__ \
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__attribute__ ((__unused__, __section__ (#set))) = &(symbol)
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# else
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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__ ((__unused__, __section__ (#set))) = &(symbol)
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# endif
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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 __attribute__ ((__weak__)); \
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extern void *const __stop_##set __attribute__ ((__weak__)); \
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weak_extern (__start_##set) weak_extern (__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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# ifdef HAVE_XCOFF
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/* XCOFF does not support .stabs.
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The native aix linker will remove the .stab and .stabstr sections
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The gnu linker will have a fatal error if there is a relocation for
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symbol in the .stab section. Silently disable these macros. */
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# define text_set_element(set, symbol)
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# define data_set_element(set, symbol)
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# define bss_set_element(set, symbol)
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# else
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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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# endif /* XCOFF */
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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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#else
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/* We cannot do anything in generial. */
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# define text_set_element(set, symbol) asm ("")
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# define data_set_element(set, symbol) asm ("")
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# define bss_set_element(set, symbol) asm ("")
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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 /* Have GNU ld. */
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#if DO_VERSIONING
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# define symbol_version(real, name, version) \
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_symbol_version(real, name, version)
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# define default_symbol_version(real, name, version) \
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_default_symbol_version(real, name, version)
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# ifdef __ASSEMBLER__
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# define _symbol_version(real, name, version) \
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.symver real, name##@##version
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# define _default_symbol_version(real, name, version) \
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.symver real, name##@##@##version
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# else
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# define _symbol_version(real, name, version) \
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__asm__ (".symver " #real "," #name "@" #version)
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# define _default_symbol_version(real, name, version) \
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__asm__ (".symver " #real "," #name "@@" #version)
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# endif
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#else
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# define symbol_version(real, name, version)
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# define default_symbol_version(real, name, version) \
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strong_alias(real, name)
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#endif
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#endif /* libc-symbols.h */
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