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

[Hans Wennborg via llvm-dev]

Ah, I see it's r338042. I'll get that merged to 7.0.

On Wed, Aug 8, 2018 at 4:58 PM, Andrew Kelley <superjoe30 at gmail.com> wrote:
> Hans,
>
> Apologies for not updating the list. I went through the formal
> reviews.llvm.org process, and this has already been merged into trunk, I
> believe.
>
> Regards,
> Andrew
>
> On Wed, Aug 8, 2018, 10:50 AM Hans Wennborg <hans at chromium.org> wrote:
>>
>> +Rui and Peter
>>
>> On Wed, Jul 25, 2018 at 8:34 AM, Andrew Kelley via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> > Here's a fix:
>> >
>> > --- a/lld/COFF/Driver.cpp
>> > +++ b/lld/COFF/Driver.cpp
>> > @@ -72,6 +72,9 @@ bool link(ArrayRef<const char *> Args, bool
>> > CanExitEarly,
>> > raw_ostream &Diag) {
>> >      exitLld(errorCount() ? 1 : 0);
>> >
>> >    freeArena();
>> > +  ObjFile::Instances.clear();
>> > +  ImportFile::Instances.clear();
>> > +  BitcodeFile::Instances.clear();
>> >    return !errorCount();
>> >  }
>> >
>> > I don't know how to make a test for this, since it depends on running
>> > LLD
>> > twice in the same process.
>> >
>> > Can I get some assistance trying to get this fix upstreamed?
>> >
>> > On Wed, Jul 25, 2018 at 2:18 AM, Andrew Kelley <superjoe30 at gmail.com>
>> > wrote:
>> >>
>> >> 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
>> >
>> >
>> >
>> > _______________________________________________
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>> >