This patch implements the C/C++ requirement that falling off main
returns zero. The easiest way to do this is to simply initialize the
return-value alloca to zero at the start of the function.
This is a pretty obvious patch, but this is my first foray into codegen,
so maybe I'm doing this horridly wrong.
John.
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp (revision 77045)
+++ lib/CodeGen/CGCall.cpp (working copy)
@@ -505,6 +505,13 @@ void CodeGenModule::ConstructAttributeLi
void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
llvm::Function *Fn,
const FunctionArgList &Args) {
+
+ // If this is main, initialize the return value to zero.
+ // Implements C++ [basic.start.main]p5 and C99 5.1.2.2.3.
+ if (const FunctionDecl* FD = dyn_cast<FunctionDecl>(CurFuncDecl))
+ if (FD->isMain())
+ Builder.CreateStore(llvm::ConstantInt::get(LLVMIntTy, 0), ReturnValue);
+
// FIXME: We no longer need the types from FunctionArgList; lift up and
// simplify.
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