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yann@1
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Suggested by Jake Page <jake at cs dot stanford dot edu>
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yann@1
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in http://sources.redhat.com/ml/crossgcc/2004-07/msg00169.html
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yann@1
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but the libc-symbols.h fragment has been reworked to fix typos
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yann@1
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and to still work on gcc-2.95.3, which lacks _Pragma.
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yann@1
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5 |
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yann@1
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His comment was:
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yann@1
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Fixes gcc-3.4 optimizing out comparisons to weak external symbols in code
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yann@1
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like:
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yann@1
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if (__pthread_mutex_init != NULL)
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yann@1
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__pthread_mutex_init(...);
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yann@1
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that causes segfaults during libc init when not linked to libpthread
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yann@1
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yann@1
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diff -uNr glibc-2.2.5-orig/resolv/res_libc.c glibc-2.2.5/resolv/res_libc.c
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yann@1
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--- glibc-2.2.5-orig/resolv/res_libc.c 2001-02-12 12:23:34.000000000 -0800
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yann@1
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+++ glibc-2.2.5/resolv/res_libc.c 2004-07-27 22:56:32.000000000 -0700
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yann@1
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@@ -84,7 +84,8 @@
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yann@1
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yann@1
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#if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_2)
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yann@1
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# undef res_init
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yann@1
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-strong_alias (__res_init, __res_init_weak);
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yann@1
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+extern int __res_init_weak (void);
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yann@1
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weak_extern (__res_init_weak);
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yann@1
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+strong_alias (__res_init, __res_init_weak);
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yann@1
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compat_symbol (libc, __res_init_weak, res_init, GLIBC_2_0);
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yann@1
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#endif
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yann@1
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--- glibc-2.2.5/include/libc-symbols.h.old Fri Aug 13 04:20:55 2004
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yann@1
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+++ glibc-2.2.5/include/libc-symbols.h Fri Aug 13 04:37:06 2004
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yann@1
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@@ -108,10 +108,16 @@
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yann@1
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yann@1
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/* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */
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yann@1
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# define weak_extern(symbol) _weak_extern (symbol)
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yann@1
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-# ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
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yann@1
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-# define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol);
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yann@1
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-# else
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yann@1
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-# define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol);
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yann@1
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+# if __GNUC__ >= 3
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yann@1
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+ /* see http://sources.redhat.com/ml/libc-alpha/2003-01/msg00043.html */
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yann@1
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+# define __weak_extern_1(expr) _Pragma(#expr)
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yann@1
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+# define _weak_extern(symbol) __weak_extern_1(weak symbol)
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yann@1
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+# else /* __GNUC__ == 2 */
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yann@1
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+# ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
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yann@1
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+# define _weak_extern(symbol) asm (".weakext " __SYMBOL_PREFIX #symbol);
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yann@1
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+# else
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yann@1
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+# define _weak_extern(symbol) asm (".weak " __SYMBOL_PREFIX #symbol);
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yann@1
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+# endif
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yann@1
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# endif
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yann@1
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yann@1
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# else
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