CodeGen

I’m learning the clang source code,try to understand how llvm translate .cpp to .ll
when I read the CodeGenModule.cpp

02271 if (GV->getType()->getElementType() != Ty) {
02272 // If the types mismatch then we have to rewrite the definition.
02273 assert(GV->isDeclaration() && “Shouldn’t replace non-declaration”);
02274
02275 // F is the Function* for the one with the wrong type, we must make a new
02276 // Function* and update everything that used F (a declaration) with the new
02277 // Function* (which will be a definition).
02278 //
02279 // This happens if there is a prototype for a function
02280 // (e.g. “int f()”) and then a definition of a different type
02281 // (e.g. “int f(int x)”). Move the old function aside so that it
02282 // doesn’t interfere with GetAddrOfFunction.
02283 GV->setName(StringRef());
02284 auto *NewFn = castllvm::Function(GetAddrOfFunction(GD, Ty));
02285
02286 // This might be an implementation of a function without a
02287 // prototype, in which case, try to do special replacement of
02288 // calls which match the new prototype. The really key thing here
02289 // is that we also potentially drop arguments from the call site
02290 // so as to make a direct call, which makes the inliner happier
02291 // and suppresses a number of optimizer warnings (!) about
02292 // dropping arguments.
02293 if (!GV->use_empty()) {
02294 ReplaceUsesOfNonProtoTypeWithRealFunction(GV, NewFn);
02295 GV->removeDeadConstantUsers();
02296 }
02297
02298 // Replace uses of F with the Function we will endow with a body.
02299 if (!GV->use_empty()) {
02300 llvm::Constant *NewPtrForOldDecl =
02301 llvm::ConstantExpr::getBitCast(NewFn, GV->getType());
02302 GV->replaceAllUsesWith(NewPtrForOldDecl);
02303 }
02304
02305 // Ok, delete the old function now, which is dead.
02306 GV->eraseFromParent();
02307
02308 GV = NewFn;
02309 }

I have a test

//aa.c

#include <stdio.h>

void fun(int a,int b);

void fun()
{
printf(“no parameters\n”);
}
int main()
{
fun();
return 0;
}

compiler using clang

aa.c:11:6: error: too few arguments to function call, expected 2, have 0
fun();

aa.c:5:1: note: 'fun' declared here
void fun()
^
1 error generated.

This Is it right?

There is no function overloading in C. Change your file’s extension to cpp.