Hi again, This may be a GOLD bug, or at least an interaction between GOLD and GCC. If I remove my "-fuse-ld=gold" line from the linker I get the correct results too: Dump of assembler code for function std::_List_node<std::function<void ()> >::~_List_node(): 0x000000000077ca80 <+0>: push %rbp 0x000000000077ca81 <+1>: mov %rsp,%rbp 0x000000000077ca84 <+4>: sub $0x10,%rsp 0x000000000077ca88 <+8>: mov %rdi,-0x8(%rbp) 0x000000000077ca8c <+12>: mov -0x8(%rbp),%rax 0x000000000077ca90 <+16>: add $0x10,%rax 0x000000000077ca94 <+20>: mov %rax,%rdi 0x000000000077ca97 <+23>: callq 0x4ff6f0 <std::function<void ()>::~function()@plt> 0x000000000077ca9c <+28>: nop 0x000000000077ca9d <+29>: leaveq 0x000000000077ca9e <+30>: retq End of assembler dump. Can a gold expert (@ilt?) help me gather the information needed to file a bug? Thanks so much in advance, Matt On Wed, Mar 16, 2016 at 3:34 PM, Matt Godbolt <matt@xxxxxxxxxxx> wrote: > Hi all, > > I've just lost a day to tracking down an unusual crash which I've > traced back to what seems to be an LTO issue. > > I'm linking a large application against some open source libraries. > All are built with the same version of GCC (5.2.0). We have been using > LTO for a long time, since 4.9.x, without issue. > > Recently I upgraded one of our dependencies > (https://github.com/mattgodbolt/seasocks). One change was that this > dependency now uses std::function<void()> in its API. This library is > built *without* LTO. > > In our application we now get a crash when the destructor for > std::function<void()> is called. We have a std::list<> of such > functions and the code generated now looks like this: > > gdb out/dist/lib-haswell/hippo -ex "disassemble > 'std::_List_node<std::function<void ()> >::~_List_node()'" > Dump of assembler code for function std::_List_node<std::function<void > ()> >::~_List_node(): > 0x0000000000763a40 <+0>: push %rbp > 0x0000000000763a41 <+1>: mov %rsp,%rbp > 0x0000000000763a44 <+4>: sub $0x10,%rsp > 0x0000000000763a48 <+8>: mov %rdi,-0x8(%rbp) > 0x0000000000763a4c <+12>: mov -0x8(%rbp),%rax > 0x0000000000763a50 <+16>: add $0x10,%rax > 0x0000000000763a54 <+20>: mov %rax,%rdi > 0x0000000000763a57 <+23>: callq 0x0 > 0x0000000000763a5c <+28>: nop > 0x0000000000763a5d <+29>: leaveq > 0x0000000000763a5e <+30>: retq > End of assembler dump. > > The spot where the "call std::function::~function<void()>" should be > has a "callq 0x0". If I build with LTO off globally, the callq is > indeed correctly generated/linked. > > It's as if the linker has just plain not done its job there with LTO on. > > If I take the source of Seasocks and bring it into the project (and > thus the files are built with LTO), all compiles fine. We run using > -fuse-ld=gold -flto -fuse-linker-plugin, amongst many other options. > > Despite trying my hardest I was unable to reproduce this issue using > two files calling each other (one with LTO on, one not). Can anyone > give suggestions as to what I might try to figure out what's going on? > I have just tried with GCC 5.3 too, and have had no success either. > > Many thanks in advance, > > Matt -- Matt
