[llvm-dev] llvm/clang 7.0 crash

[Christophe Duvernois via llvm-dev]

Hi,

I'm just trying to create a TargetMachine.  I'm using llvm 7.0
The following snippet works as expected with gcc on Ubuntu 16.04 and 18.04
but I have a crash with clang.
Am I doing something wrong here or is it a clang issue?

#include <memory>
#include <llvm/ADT/Triple.h>
#include <llvm/CodeGen/CommandFlags.inc>
#include <llvm/Support/CodeGen.h>
#include <llvm/InitializePasses.h>
#include <llvm/LinkAllIR.h>
#include <llvm/LinkAllPasses.h>
#include <llvm/MC/SubtargetFeature.h>
#include <llvm/Support/TargetRegistry.h>
#include <llvm/Support/TargetSelect.h>
#include <llvm/Target/TargetMachine.h>

using namespace llvm;

// Returns the TargetMachine instance or zero if no triple is provided.
static TargetMachine* GetTargetMachine(Triple TheTriple, StringRef CPUStr,
StringRef FeaturesStr,
const TargetOptions &Options) {
std::string Error;
const Target *TheTarget = TargetRegistry::lookupTarget(MArch, TheTriple,
Error);
// Some modules don't specify a triple, and this is okay.
if (!TheTarget) {
return nullptr;
}

return TheTarget->createTargetMachine(TheTriple.getTriple(), CPUStr,
FeaturesStr, Options, getRelocModel(),
getCodeModel(), CodeGenOpt::Default);
}

//-----------------------------------------------------------------------------
int main(int argc, const char** argv) {
    InitializeAllTargets();
    InitializeAllTargetMCs();
    InitializeAllAsmPrinters();
    InitializeAllAsmParsers();

    Triple ModuleTriple(sys::getProcessTriple());
    std::string CPUStr, FeaturesStr;
    TargetMachine* Machine = nullptr;
    const TargetOptions Options = InitTargetOptionsFromCodeGenFlags();

    if (ModuleTriple.getArch()) {
        CPUStr = getCPUStr();
        FeaturesStr = getFeaturesStr();
        Machine = GetTargetMachine(ModuleTriple, CPUStr, FeaturesStr,
Options);
    }
    std::unique_ptr<TargetMachine> TM(Machine);
    fprintf(stderr, "%s:%d %p\n", __FUNCTION__, __LINE__, TM.get());

    return 0;
}

OK : g++ -std=c++11 crash.cpp -ocrash -I`llvm-config --includedir`
-L`llvm-config --libdir` `llvm-config --libs` `llvm-config --system-libs`
CRASH : clang++ -std=c++11 crash.cpp -ocrash -I`llvm-config --includedir`
-L`llvm-config --libdir` `llvm-config --libs` `llvm-config --system-libs`

Here is the valgrind output in case of binary built with clang:
==3931== Memcheck, a memory error detector
==3931== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==3931== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==3931== Command: ./crash
==3931==
==3931== Use of uninitialised value of size 8
==3931==    at 0xF04483:
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
llvm::Optional<llvm::CodeModel::Model>, llv
m::CodeGenOpt::Level, bool) (in /home/christophe/crash)
==3931==    by 0x4D52AF: llvm::Target::createTargetMachine(llvm::StringRef,
llvm::StringRef, llvm::StringRef, llvm::TargetOptions const&,
llvm::Optional<llvm::Reloc::Model>, llvm::Optional<llvm::CodeModel::Model>,
llvm::CodeGenOpt::Level, bool) const (in /home/christophe
/crash)
==3931==    by 0x4C027C: GetTargetMachine(llvm::Triple, llvm::StringRef,
llvm::StringRef, llvm::TargetOptions const&) (in /home/christophe/crash)
==3931==    by 0x4BF492: main (in /home/christophe/crash)
==3931==
==3931== Invalid read of size 1
==3931==    at 0xF04483:
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
llvm::Optional<llvm::CodeModel::Model>, llv
m::CodeGenOpt::Level, bool) (in /home/christophe/crash)
==3931==    by 0x4D52AF: llvm::Target::createTargetMachine(llvm::StringRef,
llvm::StringRef, llvm::StringRef, llvm::TargetOptions const&,
llvm::Optional<llvm::Reloc::Model>, llvm::Optional<llvm::CodeModel::Model>,
llvm::CodeGenOpt::Level, bool) const (in /home/christophe
/crash)
==3931==    by 0x4C027C: GetTargetMachine(llvm::Triple, llvm::StringRef,
llvm::StringRef, llvm::TargetOptions const&) (in /home/christophe/crash)
==3931==    by 0x4BF492: main (in /home/christophe/crash)
==3931==  Address 0xfefffd04 is not stack'd, malloc'd or (recently) free'd
==3931==
==3931==
==3931== Process terminating with default action of signal 11 (SIGSEGV)
==3931==  Access not within mapped region at address 0xFEFFFD04
==3931==    at 0xF04483:
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
llvm::Optional<llvm::CodeModel::Model>, llv
m::CodeGenOpt::Level, bool) (in /home/christophe/crash)
==3931==    by 0x4D52AF: llvm::Target::createTargetMachine(llvm::StringRef,
llvm::StringRef, llvm::StringRef, llvm::TargetOptions const&,
llvm::Optional<llvm::Reloc::Model>, llvm::Optional<llvm::CodeModel::Model>,
llvm::CodeGenOpt::Level, bool) const (in /home/christophe
/crash)
==3931==    by 0x4C027C: GetTargetMachine(llvm::Triple, llvm::StringRef,
llvm::StringRef, llvm::TargetOptions const&) (in /home/christophe/crash)
==3931==    by 0x4BF492: main (in /home/christophe/crash)
==3931==  If you believe this happened as a result of a stack
==3931==  overflow in your program's main thread (unlikely but
==3931==  possible), you can try to increase the size of the
==3931==  main thread stack using the --main-stacksize= flag.
==3931==  The main thread stack size used in this run was 8388608.
==3931==

Best regards,
Christpohe
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