llvm dev - May 2019 - Why does verifyFunction dislike this?

I am programmatically building some functions in intermediate
representation, and trying to verify them, but the verifier always reports
that there is a problem, and I can't see why. Minimal test case:

#ifdef _MSC_VER
#pragma warning(disable : 4141)
#pragma warning(disable : 4530)
#pragma warning(disable : 4624)
#endif

#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/Verifier.h>
using namespace llvm;

int main(int argc, char **argv) {
  LLVMContext context;
  IRBuilder<> builder(context);
  Module module("", context);

  // Function
  auto rty = Type::getInt32Ty(context);
  SmallVector<Type *, 1> pty;
  auto ty = FunctionType::get(rty, pty, false);
  auto f = Function::Create(ty, GlobalValue::CommonLinkage, "f",
module);

  // Entry block
  auto entry = BasicBlock::Create(context, "entry", f);
  builder.SetInsertPoint(entry);

  // return 0
  auto val = ConstantInt::getSigned(rty, 0);
  builder.CreateRet(val);

  // Check
  f->dump();
  outs() << verifyFunction(*f) << '\n';
  return 0;
}

Output:

define common i32 @f() {
entry:
  ret i32 0
}

1

So the verifier says there is a problem, but I don't see anywhere the
problem could be. What am I missing?
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Hi Russell. 
Disclaimer: I haven't created IR from scratch nor have I used IRBuilder or
Verifier before.

There is a second parameter in verifyFunction which is the output stream it
should write error messages to in case errors occur.

Just from looking at the output I see that f is not mangled, maybe that could be
a problem?
Try Mangler::getNameWithPrefix(...) from "llvm/IR/Manger.h"

Regards,
Viktor

On May 13, 2019, 00:55, at 00:55, Russell Wallace via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>I am programmatically building some functions in intermediate
>representation, and trying to verify them, but the verifier always
>reports
>that there is a problem, and I can't see why. Minimal test case:
>
>#ifdef _MSC_VER
>#pragma warning(disable : 4141)
>#pragma warning(disable : 4530)
>#pragma warning(disable : 4624)
>#endif
>
>#include <llvm/IR/IRBuilder.h>
>#include <llvm/IR/Verifier.h>
>using namespace llvm;
>
>int main(int argc, char **argv) {
>  LLVMContext context;
>  IRBuilder<> builder(context);
>  Module module("", context);
>
>  // Function
>  auto rty = Type::getInt32Ty(context);
>  SmallVector<Type *, 1> pty;
>  auto ty = FunctionType::get(rty, pty, false);
>auto f = Function::Create(ty, GlobalValue::CommonLinkage, "f",
module);
>
>  // Entry block
>  auto entry = BasicBlock::Create(context, "entry", f);
>  builder.SetInsertPoint(entry);
>
>  // return 0
>  auto val = ConstantInt::getSigned(rty, 0);
>  builder.CreateRet(val);
>
>  // Check
>  f->dump();
>  outs() << verifyFunction(*f) << '\n';
>  return 0;
>}
>
>Output:
>
>define common i32 @f() {
>entry:
>  ret i32 0
>}
>
>1
>
>So the verifier says there is a problem, but I don't see anywhere the
>problem could be. What am I missing?
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>LLVM Developers mailing list
>llvm-dev at lists.llvm.org
>https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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On Mon, May 13, 2019 at 12:26 AM Viktor Was BSc <gs15m015 at
technikum-wien.at>
wrote:
> Hi Russell.
> Disclaimer: I haven't created IR from scratch nor have I used IRBuilder
or
> Verifier before.
>
> There is a second parameter in verifyFunction which is the output stream
> it should write error messages to in case errors occur.
>
>
Ah, that led to a solution, thanks! Now the verifier reports the specific
problem: functions may not have common linkage. When I change it to
external linkage, the verifier is happy.
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