[llvm-dev] LLD COFF library: crashes when lld::coff::link is called twice

[Andrew Kelley via llvm-dev]

If you call lld::coff::link twice, the second time gives this backtrace:

     msvcp140d.dll!00007ffc35830806()    Unknown
>    zig.exe!std::_Debug_pointer<lld::coff::Chunk * __ptr64
const>(lld::coff::Chunk * const * _Ptr, const wchar_t * _File, unsigned int
_Line) Line 926    C++
     zig.exe!std::_Debug_range2<lld::coff::Chunk * __ptr64 const *
__ptr64>(lld::coff::Chunk * const * _First, lld::coff::Chunk * const *
_Last, const wchar_t * _File, unsigned int _Line,
std::random_access_iterator_tag __formal) Line 958    C++
     zig.exe!std::_Debug_range<lld::coff::Chunk * __ptr64 const *
__ptr64>(lld::coff::Chunk * const * _First, lld::coff::Chunk * const *
_Last, const wchar_t * _File, unsigned int _Line) Line 968    C++
     zig.exe!std::vector<lld::coff::Chunk *
__ptr64,std::allocator<lld::coff::Chunk * __ptr64>
>::_Insert<lld::coff::Chunk * __ptr64 const *
__ptr64>(std::_Vector_const_iterator<std::_Vector_val<std::_Simple_types<lld::coff::Chunk
*> > > _Where, lld::coff::Chunk * const * _First, lld::coff::Chunk * const
* _Last, std::forward_iterator_tag __formal) Line 1421    C++
     zig.exe!std::vector<lld::coff::Chunk *
__ptr64,std::allocator<lld::coff::Chunk * __ptr64>
>::insert<lld::coff::Chunk * __ptr64 const *
__ptr64>(std::_Vector_const_iterator<std::_Vector_val<std::_Simple_types<lld::coff::Chunk
*> > > _Where, lld::coff::Chunk * const * _First, lld::coff::Chunk * const
* _Last) Line 1376    C++
     zig.exe!lld::coff::SymbolTable::getChunks() Line 311    C++
     zig.exe!`anonymous namespace'::Writer::createSections() Line 340    C++
     zig.exe!`anonymous namespace'::Writer::run() Line 288    C++
     zig.exe!lld::coff::writeResult() Line 166    C++
     zig.exe!lld::coff::LinkerDriver::link(llvm::ArrayRef<char const *>
ArgsArr) Line 1331    C++
     zig.exe!lld::coff::link(llvm::ArrayRef<char const *> Args, bool
CanExitEarly, llvm::raw_ostream & Diag) Line 71    C++
     zig.exe!ZigLLDLink(ZigLLVM_ObjectFormatType oformat, const char * *
args, unsigned __int64 arg_count, void(*)(void *, const char *, unsigned
__int64) append_diagnostic, void * context) Line 837    C++
     zig.exe!zig_lld_link(ZigLLVM_ObjectFormatType oformat, const char * *
args, unsigned __int64 arg_count, Buf * diag) Line 435    C++
     zig.exe!codegen_link(CodeGen * g, const char * out_file) Line 1020
C++
     zig.exe!main(int argc, char * * argv) Line 909    C++
     [External Code]

It appears that in this code, ObjFile::Instance is garbage data:

std::vector<Chunk *> SymbolTable::getChunks() {
  std::vector<Chunk *> Res;
  for (ObjFile *File : ObjFile::Instances) {
    ArrayRef<Chunk *> V = File->getChunks();
    Res.insert(Res.end(), V.begin(), V.end());
  }
  return Res;
}

When I go to the definition of ObjFile::Instances, it appears to be static
data:

  static std::vector<ObjFile *> Instances;

It appears that LLD is not resetting this data between calls. On the other
hand, lld::elf::link and lld::macho::link work no problem when called
multiple times in the same process.

My understanding is that there is supposed to be an arena allocator, which
is freed here:

bool link(ArrayRef<const char *> Args, bool CanExitEarly, raw_ostream
&Diag) {
  // ...

  Driver = make<LinkerDriver>();
  Driver->link(Args);

  // Call exit() if we can to avoid calling destructors.
  if (CanExitEarly)
    exitLld(errorCount() ? 1 : 0);

  freeArena();  // <------ here
  return !errorCount();
}

Is there a simple fix for this?

Downstream issue reference: https://github.com/ziglang/zig/issues/1289

Thanks,
Andrew
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180725/2dfc2505/attachment.html>