Hi, you need the following fix to GCC to output symbol table correctly. I will commit it after testing. Index: ipa.c =================================================================== --- ipa.c (revision 175350) +++ ipa.c (working copy) @@ -542,13 +542,13 @@ { int i; struct ipa_ref *ref; - for (i = 0; ipa_ref_list_reference_iterate (&node->ref_list, i, ref); i++) + for (i = 0; ipa_ref_list_refering_iterate (&node->ref_list, i, ref); i++) if (ref->use == IPA_REF_ADDR) { struct varpool_node *node; - if (ref->refered_type == IPA_REF_CGRAPH) + if (ref->refering_type == IPA_REF_CGRAPH) return true; - node = ipa_ref_varpool_node (ref); + node = ipa_ref_refering_varpool_node (ref); if (!DECL_VIRTUAL_P (node->decl)) return true; } With fixed GCC the following testcase fails with GNU LD but not with Gold: evans:/abuild/jh/dealIIb/:[0]# cat a.h inline int test (void) { } typedef int (*test_t) (void); evans:/abuild/jh/dealIIb/:[0]# cat a.cc #include "a.h" extern "C" void abort (); test_t b(void); int main(void) { if (test != b ()) abort (); } evans:/abuild/jh/dealIIb/:[0]# cat b.cc #include <stdio.h> #include "a.h" test_t b(void) { return test; } evans:/abuild/jh/dealIIb/:[0]# /abuild/jh/trunk-install/bin/g++ a.cc -flto -c -O2 evans:/abuild/jh/dealIIb/:[0]# /abuild/jh/trunk-install/bin/g++ b.cc -c -O2 evans:/abuild/jh/dealIIb/:[0]# /abuild/jh/trunk-install/bin/g++ a.o b.o -save-temps -O2 -flto -fuse-linker-plugin [Leaving LTRANS /tmp/cc7tSz5y.args] [Leaving LTRANS /tmp/ccAl4bQf.ltrans.out] [Leaving LTRANS /tmp/cc0AoaEb.args] [Leaving LTRANS /tmp/ccAl4bQf.ltrans0.o] evans:/abuild/jh/dealIIb/:[0]# ./a.out Aborted (core dumped) evans:/abuild/jh/dealIIb/:[134]# /abuild/jh/trunk-install/bin/g++ a.o b.o -save-temps -O2 evans:/abuild/jh/dealIIb/:[0]# ./a.out evans:/abuild/jh/dealIIb/:[0]# more ./-lm.res 1 a.o 3 164 623d5db5 PREVAILING_DEF_IRONLY _Z4testv 170 623d5db5 PREVAILING_DEF main 181 623d5db5 RESOLVED_EXEC _Z1bv I.e. with LTO compilation the _Z4testv is not merged. Golds variant of -lm.res is: 1 a.o 3 164 623d5db5 PREVAILING_DEF _Z4testv 170 623d5db5 PREVAILING_DEF main 181 623d5db5 RESOLVED_EXEC _Z1bv
Works for me with the current bfd linker: [hjl@gnu-6 pr12942]$ make /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -O2 -flto -c -o a.o a.cc /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -O2 -c -o b.o b.cc /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -O2 -flto -fuse-linker-plugin -o x a.o b.o ./x [hjl@gnu-6 pr12942]$ /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -O2 -fuse-linker-plugin -flto=jobserver -o x a.o b.o --save-temps [Leaving LTRANS /tmp/ccyenCIi.args] [Leaving LTRANS x.ltrans.out] [Leaving LTRANS /tmp/ccLMrqHc.mk] [Leaving LTRANS x.ltrans0.o] [hjl@gnu-6 pr12942]$ cat ./-lm.res 1 a.o 3 164 18e9d954 PREEMPTED_REG _Z4testv 170 18e9d954 PREVAILING_DEF main 181 18e9d954 RESOLVED_EXEC _Z1bv [hjl@gnu-6 pr12942]$
Here is the real testcase: [hjl@gnu-6 pr12942]$ cat a.h extern void link_error (); inline int test (void) { int exp = -1; if ((exp < 2 ? 2U : (unsigned int) exp) != 2) link_error (); return 0; } typedef int (*test_t) (void); [hjl@gnu-6 pr12942]$ cat a.cc #include "a.h" extern "C" void abort (); test_t b(void); int main(void) { if (test != b ()) abort (); } [hjl@gnu-6 pr12942]$ cat b.cc #include <stdio.h> #include "a.h" test_t b(void) { return test; } [hjl@gnu-6 pr12942]$ make /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -flto -c -o a.o a.cc /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -c -o b.o b.cc /export/build/gnu/gcc/build-x86_64-linux/gcc/../../release/usr/gcc-4.7.0/bin/g++ -O2 -flto -fuse-linker-plugin -B./ -o x a.o b.o b.o: In function `test()': b.cc:(.text._Z4testv[test()]+0x16): undefined reference to `link_error()' collect2: error: ld returned 1 exit status make: *** [x] Error 1 [hjl@gnu-6 pr12942]$ Gold works fine. The problem is BFD linker failed to pick the correct definition.
There are at least 2 problems: 1. plugin totally ignores comdat_key. 2. section for plugin symbol with comdat_key should override other sections with the same comdat_key.
CVSROOT: /cvs/src Module name: src Changes by: amodra@sourceware.org 2011-07-09 06:20:52 Modified files: bfd : ChangeLog elflink.c cofflink.c elf-bfd.h libbfd-in.h libbfd.h linker.c targets.c bfd-in2.h include : ChangeLog bfdlink.h ld : ChangeLog ldlang.c plugin.c Log message: PR ld/12942 bfd/ * elflink.c (elf_link_add_object_symbols): Use elf_discarded_section rather than kept_section to determine whether a symbol is from a discarded section. * cofflink.c (coff_link_add_symbols): Make symbols from discarded sections appear undefined. * elf-bfd.h (_bfd_elf_section_already_linked): Replace "asection *" with "struct already_linked *". * libbfd-in.h (_bfd_nolink_section_already_linked): Likewise. (_bfd_generic_section_already_linked): Likewise. (bfd_section_already_linked_table_insert): Likewise. (struct already_linked): New. (struct bfd_section_already_linked): Use it. * elflink.c (_bfd_elf_section_already_linked): Replace. "asection *" with "struct already_linked *". Replace the plugin dummy with the LTO output. * linker.c (_bfd_generic_section_already_linked): Likewise. * targets.c (struct already_linked): Add forward declaration. (bfd_target): Replace "struct bfd_section *" with "struct already_linked *" in _section_already_linked. * bfd-in2.h: Regenerate. * libbfd.h: Regenerate. include/ * bfdlink.h (bfd_link_info): Add loading_lto_outputs. ld/ * ldlang.c (section_already_linked): Pass "struct already_linked *" to bfd_section_already_linked. (lang_process): Set link_info.loading_lto_outputs before loading LTO outputs. * plugin.c: Include "libbfd.h". (add_symbols): Call bfd_section_already_linked with comdat_key. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/ChangeLog.diff?cvsroot=src&r1=1.5417&r2=1.5418 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elflink.c.diff?cvsroot=src&r1=1.412&r2=1.413 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/cofflink.c.diff?cvsroot=src&r1=1.77&r2=1.78 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf-bfd.h.diff?cvsroot=src&r1=1.323&r2=1.324 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/libbfd-in.h.diff?cvsroot=src&r1=1.88&r2=1.89 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/libbfd.h.diff?cvsroot=src&r1=1.253&r2=1.254 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/linker.c.diff?cvsroot=src&r1=1.85&r2=1.86 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/targets.c.diff?cvsroot=src&r1=1.202&r2=1.203 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/bfd-in2.h.diff?cvsroot=src&r1=1.540&r2=1.541 http://sourceware.org/cgi-bin/cvsweb.cgi/src/include/ChangeLog.diff?cvsroot=src&r1=1.541&r2=1.542 http://sourceware.org/cgi-bin/cvsweb.cgi/src/include/bfdlink.h.diff?cvsroot=src&r1=1.88&r2=1.89 http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/ChangeLog.diff?cvsroot=src&r1=1.2350&r2=1.2351 http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/ldlang.c.diff?cvsroot=src&r1=1.372&r2=1.373 http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/plugin.c.diff?cvsroot=src&r1=1.35&r2=1.36
Works in 2.23.
CVSROOT: /cvs/src Module name: src Changes by: amodra@sourceware.org 2013-04-03 11:44:41 Modified files: ld/testsuite : ChangeLog ld/testsuite/ld-plugin: lto.exp pr12942a.cc Log message: PR ld/15227 * ld-plugin/lto.exp (PR ld/12942 (3)): Remove file name and line number from regexp. (PR ld/15146 (2)): Similarly. * ld-plugin/pr12942a.cc (main): Use __builtin_abort. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/testsuite/ChangeLog.diff?cvsroot=src&r1=1.1704&r2=1.1705 http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/testsuite/ld-plugin/lto.exp.diff?cvsroot=src&r1=1.7&r2=1.8 http://sourceware.org/cgi-bin/cvsweb.cgi/src/ld/testsuite/ld-plugin/pr12942a.cc.diff?cvsroot=src&r1=1.1&r2=1.2
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "gdb and binutils". The branch, master has been updated via b53dfeb26ed06e97fff1e8f469e33637ebdf6624 (commit) from a841bdf5d3bfb9c687f938be7388597db2e461de (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b53dfeb26ed06e97fff1e8f469e33637ebdf6624 commit b53dfeb26ed06e97fff1e8f469e33637ebdf6624 Author: Alan Modra <amodra@gmail.com> Date: Sat Oct 18 21:46:48 2014 +1030 PowerPC64 ELFv1 function symbol definition vs LTO and discarded sections When functions are emitted in comdat groups, global symbols defined in duplicates of the group are treated as if they were undefined. That prevents the symbols in the discarded sections from affecting the linker's global symbol hash table or causing duplicate symbol errors. Annoyingly, when gcc emits a function to a comdat group, it does not put *all* of a function's code and data in the comdat group. Typically, constant tables, exception handling info, and debug info are emitted to normal sections outside of the group, which is a perennial source of linker problems due to the special handling needed to deal with the extra-group pieces that ought to be discarded. In the case of powerpc64-gcc, the OPD entry for a function is not put in the group. Since the function symbol is defined on the OPD entry this means we need to handle symbols in .opd specially. To see how this affects LTO in particular, consider the linker testcase PR ld/12942 (1). This testcase links an LTO object file pr12942a.o with a normal (non-LTO) object pr12942b.o. Both objects contain a definition for _Z4testv in a comdat group. On loading pr12942a.o, the linker sees a comdat group (actually linkonce section) for _Z4testv and a weak _Z4testv defined in the IR. On loading pr12942b.o, the linker sees the same comdat group, and thus discards it. However, _Z4testv is a weak symbol defined in .opd, not part of the group, so this weak symbol overrides the weak IR symbol. On (re)loading the LTO version of pr12942a.o, the linker sees another weak _Z4testv, but this one does not override the value we have from pr12942b.o. The result is a linker complaint about "`_Z4testv' ... defined in discarded section `.group' of tmpdir/pr12942b.o". * elf64-ppc.c (ppc64_elf_add_symbol_hook): If function code section for function symbols defined in .opd is discarded, let the symbol appear to be undefined. (opd_entry_value): Ensure the result section is that for the function code section in the same object as the OPD entry. ----------------------------------------------------------------------- Summary of changes: bfd/ChangeLog | 8 ++++ bfd/elf64-ppc.c | 105 ++++++++++++++++++++++++++++++++---------------------- 2 files changed, 70 insertions(+), 43 deletions(-)
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "gdb and binutils". The branch, binutils-2_25-branch has been updated via a809b386e59dfcb3f4dedd8465975dabc55db5db (commit) via 2609fe3d3f84ce62b373daa56ba615465c2d5293 (commit) via 334efb9a97018d8b2f508e5c22e5acb7b824cc76 (commit) via 35ac6b6a54f9be85dd9794fa6645fac3631e510b (commit) from 7cc2a6b6a4c63cba363836475052a71e0387e621 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a809b386e59dfcb3f4dedd8465975dabc55db5db commit a809b386e59dfcb3f4dedd8465975dabc55db5db Author: Alan Modra <amodra@gmail.com> Date: Tue Oct 21 20:44:38 2014 +1030 Relax ppc64_elf_tls_optimize assertion The code in ppc64_elf_tls_optimize looking at the .toc is only interested in .toc entries that are addresses. .toc can contain more than just an array of addresses, so if we have items that aren't 8-byte aligned, ignore them. * elf64-ppc.c (ppc64_elf_tls_optimize): Ignore relocs against toc entries that aren't a multiple of 8 rather than failing assertion. https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2609fe3d3f84ce62b373daa56ba615465c2d5293 commit 2609fe3d3f84ce62b373daa56ba615465c2d5293 Author: Jan Beulich <jbeulich@novell.com> Date: Tue Oct 21 09:56:38 2014 +0200 ppc: enable msgclr and msgsnd on Power8 According to my reading of the spec it was an oversight for them to not having got enabled when Power8 support got added. https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=334efb9a97018d8b2f508e5c22e5acb7b824cc76 commit 334efb9a97018d8b2f508e5c22e5acb7b824cc76 Author: Alan Modra <amodra@gmail.com> Date: Tue Oct 21 17:06:01 2014 +1030 Add gcc-4.9 libgomp symbols requiring --plt-thread-safe for power7 powerpc64 ld builds plt call stubs with a read barrier to provide thread safety on lazy plt updates, necessary on multi-threaded apps with power7 or later weakly ordered memory. gcc-4.9 libgomp introduced more functions that could call pthread_create, which means we have more functions that if referenced in an executable should cause a default of --plt-thread-safe. bfd/ * elf64-ppc.c (ppc64_elf_size_stubs): Add gcc-4.9 libgomp functions to thread_starter. gold/ * powerpc.cc (do_relax): Add gcc-4.9 libgomp functions to thread_starter. https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=35ac6b6a54f9be85dd9794fa6645fac3631e510b commit 35ac6b6a54f9be85dd9794fa6645fac3631e510b Author: Alan Modra <amodra@gmail.com> Date: Sat Oct 18 21:46:48 2014 +1030 PowerPC64 ELFv1 function symbol definition vs LTO and discarded sections When functions are emitted in comdat groups, global symbols defined in duplicates of the group are treated as if they were undefined. That prevents the symbols in the discarded sections from affecting the linker's global symbol hash table or causing duplicate symbol errors. Annoyingly, when gcc emits a function to a comdat group, it does not put *all* of a function's code and data in the comdat group. Typically, constant tables, exception handling info, and debug info are emitted to normal sections outside of the group, which is a perennial source of linker problems due to the special handling needed to deal with the extra-group pieces that ought to be discarded. In the case of powerpc64-gcc, the OPD entry for a function is not put in the group. Since the function symbol is defined on the OPD entry this means we need to handle symbols in .opd specially. To see how this affects LTO in particular, consider the linker testcase PR ld/12942 (1). This testcase links an LTO object file pr12942a.o with a normal (non-LTO) object pr12942b.o. Both objects contain a definition for _Z4testv in a comdat group. On loading pr12942a.o, the linker sees a comdat group (actually linkonce section) for _Z4testv and a weak _Z4testv defined in the IR. On loading pr12942b.o, the linker sees the same comdat group, and thus discards it. However, _Z4testv is a weak symbol defined in .opd, not part of the group, so this weak symbol overrides the weak IR symbol. On (re)loading the LTO version of pr12942a.o, the linker sees another weak _Z4testv, but this one does not override the value we have from pr12942b.o. The result is a linker complaint about "`_Z4testv' ... defined in discarded section `.group' of tmpdir/pr12942b.o". * elf64-ppc.c (ppc64_elf_add_symbol_hook): If function code section for function symbols defined in .opd is discarded, let the symbol appear to be undefined. (opd_entry_value): Ensure the result section is that for the function code section in the same object as the OPD entry. ----------------------------------------------------------------------- Summary of changes: bfd/ChangeLog | 15 +++++ bfd/elf64-ppc.c | 116 +++++++++++++++++++++++++--------------- gas/testsuite/ChangeLog | 4 ++ gas/testsuite/gas/ppc/power8.d | 2 + gas/testsuite/gas/ppc/power8.s | 2 + gold/ChangeLog | 7 +++ gold/powerpc.cc | 6 ++ opcodes/ChangeLog | 6 ++ opcodes/ppc-opc.c | 4 +- 9 files changed, 116 insertions(+), 46 deletions(-)