[LLVMdev] Global variable initializer type does not match global variable type

Peter Zotov whitequark at whitequark.org
Wed Jan 9 07:59:06 PST 2013


I've managed to create a bitcode file (attached; also available at [1]) 
which produces
a series of identical errors when verified:

| Global variable initializer type does not match global variable type!
| %i.NilClass* @nil

When ran through llvm-dis and recompiled, through, it verifies 
successfully. If I
disassemble it one more time, the result is identical to the first 
disassembly. The
recompiled bitcode file is slightly smaller.

I suspect that the problem is with aggregate type uniqueing. I use 
ruby-llvm bindings,
LLVM 3.2 to generate the file; the following code demonstrates what I 
deem the incorrect

    # llvm_ty is an LLVM struct type with 2 elements.
    a, b = llvm_ty.element_types
    # Here, I decompose the type and verify that the types of elements
    # match my expectations:
    p a == @types[Monotype.of(VI::Class)] # true
    p b == emit_class_body_type(klass)    # true

    # I attempt to reconstruct the type using the elements
    # and check if it's still the same.
    p llvm_ty == LLVM::Type.struct([
      ], false)                           # false. Why?

Ruby-LLVM bindings compare underlying LLVM pointers when the Type 
objects are compared
with ==.

The problem manifests itself when the following code contains the 
initializer assignment:

     datum = @llvm.globals.add llvm_ty, name
     datum.initializer = LLVM::ConstantStruct.const([
         emit_object(klass, klass_name).bitcast_to(

LLVM::ConstantStruct.const eventually calls the LLVMConstStruct method 
with the
appropriate arguments; LLVM::Constant.null corresponds to 

Any hints are greatly appreciated.

   WBR, Peter Zotov.

   [1]: http://fehu.whitequark.org/files/gvar-init.bc
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