[LLVMdev] llvmContext::removeModule doesn't remove NamedStructTypes

[Liu Xin]

Hi, LLVM community,

I found an issue in my using scenario.  We deliberately parse a bitcode
file twice. It contains  a named struct type. eg. %struct.cmd = type {
float, float, float, float, float, i32 }. In the second module->dump,
%struct.cmd becomes %struct.cmd0.

my code is simplified like this.

int main()
{
    llvm::LLVMContext &llvmCtx = llvm::getGlobalContext();
    string ErrMsg;
    string filename = "wrapper.bc";
    llvm::OwningPtr<llvm::MemoryBuffer> File;

    if (llvm::MemoryBuffer::getFileOrSTDIN(filename, File)) {
        assert(0);
    }

    llvm::MemoryBuffer * buffer = File.take();
    {
        llvm::OwningPtr<llvm::Module> module(llvm::ParseBitcodeFile(buffer,
llvmCtx, &ErrMsg));
        module->dump();
    }

    {
        llvm::OwningPtr<llvm::Module> module(llvm::ParseBitcodeFile(buffer,
llvmCtx, &ErrMsg));
        module->dump();
    }

}


with smart pointer, the 1st module will be deleted and call removeModule
for the context.  The implementation of removeModule is quite simple. It
just removes the PtrSet.

pImpl->OwnedModules.erase(M);

It doesn't touch LLVMContextImpl's NamedStructTypes.  As a result,
'struct.cmd' is still in the symbol table even the module has destroyed.
 In second ParseBitCodeFile, StructType::setName will introduce struct.cmd0
due to conflict.

should we do thorough cleanup for the method removeModule? or why does llvm
retain NamedStructTypes?

thanks,
--lx
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