createLocalVariable not generated in LLVM.cs

[yowl]

If I understand correctly LLVM.cs is autogenerated ? The debug function createLocalVariable from DIBuilder.cpp is not present, perhaps because of the SmallVector in the signature?

static DILocalVariable *createLocalVariable(
    LLVMContext &VMContext,
    DenseMap<MDNode *, SmallVector<TrackingMDNodeRef, 1>> &PreservedVariables,
    DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
    unsigned LineNo, DIType *Ty, bool AlwaysPreserve, DINode::DIFlags Flags,
    uint32_t AlignInBits) {

[tannergooding]

createLocalVariable is a private method that is part of the source files and isn't even available to normal C++ code.

LLVMSharp only exposes method signatures exported from the llvm-c public header files, notably: https://github.com/llvm/llvm-project/tree/master/llvm/include/llvm-c

[tannergooding]

C++ code has access to more, generally covering the public header files available here: https://github.com/llvm/llvm-project/tree/master/llvm/include/llvm

However, due to ABI differences and name mangling, consuming those from C#/.NET is non-trivial.

[yowl]

This one is important for getting access to locals in the debugger. I think this parameter, which seems to be to do with preventing a variable getting inlined, could be null for now and if AlwaysPreseve == false, then its not used:

static DILocalVariable *createLocalVariable(
    LLVMContext &VMContext,
    DenseMap<MDNode *, SmallVector<TrackingMDNodeRef, 1>> &PreservedVariables,
    DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
    unsigned LineNo, DIType *Ty, bool AlwaysPreserve, DINode::DIFlags Flags,
    uint32_t AlignInBits) {
  // FIXME: Why getNonCompileUnitScope()?
  // FIXME: Why is "!Context" okay here?
  // FIXME: Why doesn't this check for a subprogram or lexical block (AFAICT
  // the only valid scopes)?
  DIScope *Context = getNonCompileUnitScope(Scope);

  auto *Node =
      DILocalVariable::get(VMContext, cast_or_null<DILocalScope>(Context), Name,
                           File, LineNo, Ty, ArgNo, Flags, AlignInBits);
  if (AlwaysPreserve) {
    // The optimizer may remove local variables. If there is an interest
    // to preserve variable info in such situation then stash it in a
    // named mdnode.
    DISubprogram *Fn = getDISubprogram(Scope);
    assert(Fn && "Missing subprogram for local variable");
    PreservedVariables[Fn].emplace_back(Node);
  }
  return Node;
}

I'm going to try that with a local DllImport to see if I can get locals displaying, if it works maybe we could think about how to incorporate it, perhaps just without support for AlwaysPreserve?

[tannergooding]

I'm fairly certain you aren't meant to use that function and are instead meant to use things like DIBuilder::createAutoVariable and DIBuilder::createParameterVariable.

These are exposed via the C API as LLVMDIBuilderCreateAutoVariable and LLVMDIBuilderCreateParameterVariable, respectively.

[yowl]

Ah, you may be right, I was reading https://llvm.org/devmtg/2014-10/Slides/Christopher-DebugInfoTutorial.pdf which is very old. I'll do some more investigation on LLVMDIBuilderCreateAutoVariable