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Fix for --gc-sections on NetBSD

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This patch fixes http://bugs.ntp.org/1844, works around
http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=40401, by
improving the test for support of --gc-sections to run a program which
reads a file using stdio built with --gc-sections, instead of simply
link the binary.  This catches the buggy linker as the garbage
collection removes a tag NetBSD uses to distinguish its own elf
binaries from Linux ones, causing it to treat conftest as a Linux
binary and run it with the wrong syscall table.
This commit is contained in:
Dave Hart 2011-03-23 16:22:57 -04:00 committed by Nick Mathewson
parent b5a1f9f74b
commit 6bb23e4bb1
1 changed files with 45 additions and 7 deletions
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52
configure.in
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@ -662,26 +662,64 @@ LIBEVENT_GC_SECTIONS=
if test "$GCC" = yes && test "$enable_function_sections" = yes ; then if test "$GCC" = yes && test "$enable_function_sections" = yes ; then
AC_CACHE_CHECK( AC_CACHE_CHECK(
[if linker supports omitting unused code and data], [if linker supports omitting unused code and data],
[libevent_cv_gc_sections_works], [libevent_cv_gc_sections_runs],
[ [
dnl NetBSD will link but likely not run with --gc-sections
dnl http://bugs.ntp.org/1844
dnl http://gnats.netbsd.org/40401
dnl --gc-sections causes attempt to load as linux elf, with
dnl wrong syscalls in place. Test a little gauntlet of
dnl simple stdio read code checking for errors, expecting
dnl enough syscall differences that the NetBSD code will
dnl fail even with Linux emulation working as designed.
dnl A shorter test could be refined by someone with access
dnl to a NetBSD host with Linux emulation working.
origCFLAGS="$CFLAGS" origCFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Wl,--gc-sections" CFLAGS="$CFLAGS -Wl,--gc-sections"
AC_LINK_IFELSE( AC_LINK_IFELSE(
[AC_LANG_PROGRAM([[]], [[]])], [AC_LANG_PROGRAM(
[[
#include <stdlib.h>
#include <stdio.h>
]],
[[
FILE * fpC;
char buf[32];
size_t cch;
int read_success_once;
fpC = fopen("conftest.c", "r");
if (NULL == fpC)
exit(1);
do {
cch = fread(buf, sizeof(buf), 1, fpC);
read_success_once |= (0 != cch);
} while (0 != cch);
if (!read_success_once)
exit(2);
if (!feof(fpC))
exit(3);
if (0 != fclose(fpC))
exit(4);
exit(EXIT_SUCCESS);
]]
)],
[ [
if grep gc-sections conftest.err ; then if test "X$cross_compiling" = "Xyes" || grep gc-sections conftest.err ; then
libevent_cv_gc_sections_works=no libevent_cv_gc_sections_runs=no
else else
libevent_cv_gc_sections_works=yes libevent_cv_gc_sections_runs=no
./conftest >/dev/null 2>&1 && libevent_cv_gc_sections_runs=yes
fi fi
], ],
[libevent_cv_gc_sections_works=no] [libevent_cv_gc_sections_runs=no]
) )
CFLAGS="$origCFLAGS" CFLAGS="$origCFLAGS"
AS_UNSET([origCFLAGS]) AS_UNSET([origCFLAGS])
] ]
) )
case "$libevent_cv_gc_sections_works" in case "$libevent_cv_gc_sections_runs" in
yes) yes)
CFLAGS="-ffunction-sections -fdata-sections $CFLAGS" CFLAGS="-ffunction-sections -fdata-sections $CFLAGS"
LIBEVENT_GC_SECTIONS="-Wl,--gc-sections" LIBEVENT_GC_SECTIONS="-Wl,--gc-sections"