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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Changing the subject line and reposting the question.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Bumping up to make sure that this post was not lost during the holidays ;)<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Appreciate any feedback.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Balaram<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu] <b>On Behalf Of </b>Balaram Makam<br><b>Sent:</b> Saturday, May 24, 2014 10:04 AM<br><b>To:</b> llvmdev@cs.uiuc.edu<br><b>Subject:</b> [LLVMdev] gold linker failing to resolve weak undefined symbol<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hi,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am experimenting with an inline strategy wherein I postpone inlining to link time rather than inlining at compile time, but I am facing runtime failure and wonder if anyone else saw this.<o:p></o:p></p><p class=MsoNormal>Here is my sample test case:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>$ cat test.cpp<o:p></o:p></p><p class=MsoNormal>#include <sstream><o:p></o:p></p><p class=MsoNormal>int main() {<o:p></o:p></p><p class=MsoNormal> std::stringstream ss;<o:p></o:p></p><p class=MsoNormal> ss << "hello";<o:p></o:p></p><p class=MsoNormal> ss.str();<o:p></o:p></p><p class=MsoNormal>}<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>To test my inline strategy, I compile at O1 and use flto with gold plugin as below:<o:p></o:p></p><p class=MsoNormal>clang -O1 -flto -Wl,-fuse-ld=gold -static test.cpp –o test.exe<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>But the executable segfaults due to a weak undefined symbol:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Program received signal SIGSEGV, Segmentation fault.<o:p></o:p></p><p class=MsoNormal>0x00000000 in ?? ()<o:p></o:p></p><p class=MsoNormal>(gdb) bt<o:p></o:p></p><p class=MsoNormal>#0 0x00000000 in ?? ()<o:p></o:p></p><p class=MsoNormal>#1 0x000221e6 in std::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >::str() const ()<o:p></o:p></p><p class=MsoNormal>#2 0x00009020 in main ()<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>$ nm test.exe|grep _ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag<o:p></o:p></p><p class=MsoNormal> w _ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Note that the symbol value is null for the symbol _ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag in the symbol table.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>However, when I compile at O3 and use flto with gold plugin, the linker is able to resolve the symbol correctly and there is no runtime failure:<o:p></o:p></p><p class=MsoNormal>clang –O3 -flto -Wl,-fuse-ld=gold -static test.cpp –o test.exe<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>$ nm test.exe|grep _ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag<o:p></o:p></p><p class=MsoNormal>00030139 W _ZNSs12_S_constructIPcEES0_T_S1_RKSaIcESt20forward_iterator_tag<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Has anyone seen this issue before? Could this be an issue with the gold linker? <o:p></o:p></p><p class=MsoNormal>Is it a bad design strategy to postpone inlining to link stage?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks,<o:p></o:p></p><p class=MsoNormal>Balaram<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>