On 2/14/2011 6:10 AM, Ian Lance Taylor wrote:
The test in gcc/configure.ac is unfortunately rather misleading. That
result of that test is currently only used on Solaris.
The relevant code can be found in two places: gcc/unwind-dw2-fde-glibc.c
and gcc/crtstuff.c. In unwind-dw2-fde-glibc.c it looks like this:
#if !defined(inhibit_libc)&& defined(HAVE_LD_EH_FRAME_HDR) \
&& (__GLIBC__> 2 || (__GLIBC__ == 2&& __GLIBC_MINOR__> 2) \
|| (__GLIBC__ == 2&& __GLIBC_MINOR__ == 2&& defined(DT_CONFIG)))
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc)&& defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(__FreeBSD__)&& __FreeBSD__>= 7
# define ElfW __ElfN
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc)&& defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(TARGET_DL_ITERATE_PHDR) \
&& defined(__sun__)&& defined(__svr4__)
# define USE_PT_GNU_EH_FRAME
#endif
The idea is that USE_PT_GNU_EH_FRAME should be defined on any system for
which the linker supports --eh-frame-hdr and the library supports
dl_iterate_phdr. As you can see, the test is being done based on the
library version. It is done this way because when gcc is being used to
build the C library, particularly when building a cross-compiler, there
is no way to test the features that the C library supports.
Ian
Thanks Ian. If I understand the code in those two files correctly, only
Solaris, Linux, and FreeBSD is being considered. If I want to use this
on Dragonfly 2.9+, NetBSD 5.99+, and/or OpenBSD, I'll have to patch
these files will the appropriate code.
My FSF copyright assignment papers should have arrived to FSF by now, so
I will pass along these patches with the others.
For the others, I am waiting for gcc 4.6 to get branched. Would a
configuration patch to these files make it into trunk before it's
branched? If you take the words "regression fixes and documentation
only" literally then the answer would be no, it has to wait for 4.7 stage 1.
Regards,
John
