From http://sources.redhat.com/ml/binutils/2004-08/msg00190.html Date: Tue, 17 Aug 2004 12:04:29 +0200 From: Jakub Jelinek To: binutils at sources dot redhat dot com Subject: [PATCH] Fix `defined in discarded section' errors when building ia64 gcc Message-ID: <20040817100429.GL30497@sunsite.ms.mff.cuni.cz> Reply-To: Jakub Jelinek References: <20040817090201.GK30497@sunsite.ms.mff.cuni.cz> In-Reply-To: <20040817090201 dot GK30497 at sunsite dot ms dot mff dot cuni dot cz> On Tue, Aug 17, 2004 at 11:02:01AM +0200, Jakub Jelinek wrote: > Current gcc 3.4.x (at least gcc-3_4-rhl-branch) doesn't build with CVS > binutils (nor 2.15.91.0.2). > The problem is that libstdc++.so linking fails with: > `.gnu.linkonce.t._ZNSdD2Ev' referenced in section `.gnu.linkonce.ia64unw._ZNSdD2Ev' of .libs/sstream-inst.o: defined in discarded section `.gnu.linkonce.t._ZNSdD2Ev' of .libs/sstream-inst.o > The problem is that both io-inst.s and sstream-inst.s have > .gnu.linkonce.t._ZNSdD2Ev definition, but because io-inst.cc > also instantiates some templates sstream-inst.cc doesn't instantiate, > the inliner can do a better job in io-inst.cc. > The result is that _ZNSdD2Ev in io-inst.cc is a leaf routine, while > it is not in sstream-inst.cc (in assembly, > _ZNSdD2Ev in io-inst.s starts with .prologue and no .save directives, > while _ZNSdD2Ev] in sstream-inst.s has .prologue 12, 35 and some > .save directives. > IA-64 ABI allows leaf routines to have no unwind section at all, > which means .gnu.linkonce.ia64unw._ZNSdD2Ev is not created in > io-inst.o at all and as .gnu.linkonce.t._ZNSdD2Ev comes first > and wins, .gnu.linkonce.ia64unw._ZNSdD2Ev in sstream.o suddenly > references a discarded section. > > Not sure what should be done here, but certainly the compiler > isn't at fault here, it is a binutils problem. > One fix could be to create empty .gnu.linkonce.ia64unw.* section > in assembler, another special case ia64 unwind sections in the linker. Here is a patch for the first possibility. It certainly makes libstdc++.so to link and even the unwind info looks good on brief skimming. 2004-08-17 Jakub Jelinek * config/tc-ia64.c (start_unwind_section): Add linkonce_empty argument, don't do anything if current section is not .gnu.linkonce.t.* and linkonce_empty is set. (generate_unwind_image, dot_endp): Adjust callers, call start_unwind_section (*, 1) if nothing will be put into the section. --- binutils/gas/config/tc-ia64.c.jj 2004-07-30 11:42:24.000000000 +0200 +++ binutils/gas/config/tc-ia64.c 2004-08-17 13:45:04.288173205 +0200 @@ -1,5 +1,6 @@ /* tc-ia64.c -- Assembler for the HP/Intel IA-64 architecture. - Copyright 1998, 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc. + Copyright 1998, 1999, 2000, 2001, 2002, 2003, 2004 + Free Software Foundation, Inc. Contributed by David Mosberger-Tang This file is part of GAS, the GNU Assembler. @@ -3297,7 +3298,7 @@ static char *special_linkonce_name[] = }; static void -start_unwind_section (const segT text_seg, int sec_index) +start_unwind_section (const segT text_seg, int sec_index, int linkonce_empty) { /* Use a slightly ugly scheme to derive the unwind section names from @@ -3359,6 +3360,8 @@ start_unwind_section (const segT text_se prefix = special_linkonce_name [sec_index - SPECIAL_SECTION_UNWIND]; suffix += sizeof (".gnu.linkonce.t.") - 1; } + else if (linkonce_empty) + return; prefix_len = strlen (prefix); suffix_len = strlen (suffix); @@ -3444,7 +3447,7 @@ generate_unwind_image (const segT text_s expressionS exp; bfd_reloc_code_real_type reloc; - start_unwind_section (text_seg, SPECIAL_SECTION_UNWIND_INFO); + start_unwind_section (text_seg, SPECIAL_SECTION_UNWIND_INFO, 0); /* Make sure the section has 4 byte alignment for ILP32 and 8 byte alignment for LP64. */ @@ -3485,6 +3488,8 @@ generate_unwind_image (const segT text_s unwind.personality_routine = 0; } } + else + start_unwind_section (text_seg, SPECIAL_SECTION_UNWIND_INFO, 1); free_saved_prologue_counts (); unwind.list = unwind.tail = unwind.current_entry = NULL; @@ -4164,7 +4169,7 @@ dot_endp (dummy) subseg_set (md.last_text_seg, 0); unwind.proc_end = expr_build_dot (); - start_unwind_section (saved_seg, SPECIAL_SECTION_UNWIND); + start_unwind_section (saved_seg, SPECIAL_SECTION_UNWIND, 0); /* Make sure that section has 4 byte alignment for ILP32 and 8 byte alignment for LP64. */ @@ -4204,6 +4209,9 @@ dot_endp (dummy) bytes_per_address); } + else + start_unwind_section (saved_seg, SPECIAL_SECTION_UNWIND, 1); + subseg_set (saved_seg, saved_subseg); /* Parse names of main and alternate entry points and set symbol sizes. */ Jakub