llvm dev - Apr 2017 - Compiling a simple pass skeleton inside LLVM fails

Hi folks,

I wanted to add a function pass inside the compiler. Therefore, I added the
following pass skeleton to the compiler (which works for an out-of-tree
compilation):

#include "llvm/Pass.h"

using namespace llvm;

namespace {
  class FooPass : public FunctionPass {
  public:
    static char ID;

    FooPass() : FunctionPass(ID) {
    }

    bool runOnFunction(Function &F) override;
  };
}

bool FooPass::runOnFunction(Function &F) {
  return false;
}

char FooPass::ID = 0;
INITIALIZE_PASS_BEGIN(FooPass, "foo",
                      "My little Foo Pass", false, false)
INITIALIZE_PASS_END(FooPass, "foo",
                    "My little Foo Pass", false, false)

FunctionPass *llvm::createFooPass() {
  return new FooPass();
}

However, when compiling the compiler, the initialization of the pass seems
not to be working because I get the following error messages:

In file included from /home/work/gitprojects/llvm/include/llvm/Pass.h:377:0,
                 from
/home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:1:
/home/work/gitprojects/llvm/include/llvm/PassSupport.h:81:63: error: ‘void
llvm::initializeFooPassPass(llvm::PassRegistry&)’ should have been declared
inside ‘llvm’
   void llvm::initialize##passName##Pass(PassRegistry &Registry) { \
                                                               ^
/home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:24:1: note:
in expansion of macro ‘INITIALIZE_PASS_END’
 INITIALIZE_PASS_END(FooPass, "foo",
 ^
/home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:27:35:
error: ‘llvm::FunctionPass* llvm::createFooPass()’ should have been
declared inside ‘llvm’
 FunctionPass *llvm::createFooPass() {
                                   ^

I already looked up other passes within the compiler, but do not see the
difference why it is working there and not here.

Can someone guide me how to fix this error?

Thanks and Cheers,
Max
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Max Muster via llvm-dev <llvm-dev at lists.llvm.org>
writes:
> I wanted to add a function pass inside the compiler. Therefore, I added the
> following pass skeleton to the compiler (which works for an out-of-tree
> compilation):
>
> #include "llvm/Pass.h"
>
> using namespace llvm;
>
> namespace {
>   class FooPass : public FunctionPass {
>   public:
>     static char ID;
>
>     FooPass() : FunctionPass(ID) {
>     }
>
>     bool runOnFunction(Function &F) override;
>   };
> }
>
> bool FooPass::runOnFunction(Function &F) {
>   return false;
> }
>
> char FooPass::ID = 0;
> INITIALIZE_PASS_BEGIN(FooPass, "foo",
>                       "My little Foo Pass", false, false)
> INITIALIZE_PASS_END(FooPass, "foo",
>                     "My little Foo Pass", false, false)
>
> FunctionPass *llvm::createFooPass() {
>   return new FooPass();
> }
>
> However, when compiling the compiler, the initialization of the pass seems
> not to be working because I get the following error messages:
>
> In file included from
/home/work/gitprojects/llvm/include/llvm/Pass.h:377:0,
>                  from
> /home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:1:
> /home/work/gitprojects/llvm/include/llvm/PassSupport.h:81:63: error: ‘void
> llvm::initializeFooPassPass(llvm::PassRegistry&)’ should have been
declared
> inside ‘llvm’
>    void llvm::initialize##passName##Pass(PassRegistry &Registry) { \
>                                                                ^
> /home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:24:1: note:
> in expansion of macro ‘INITIALIZE_PASS_END’
>  INITIALIZE_PASS_END(FooPass, "foo",
>  ^
> /home/work/gitprojects/llvm/lib/Transforms/ancoder/foo_pass.cpp:27:35:
> error: ‘llvm::FunctionPass* llvm::createFooPass()’ should have been
> declared inside ‘llvm’
>  FunctionPass *llvm::createFooPass() {
>                                    ^
>
> I already looked up other passes within the compiler, but do not see the
> difference why it is working there and not here.
>
> Can someone guide me how to fix this error?
I think you're missing a forward declaration of the pass initializer in
the llvm namespace. See the declarations in "llvm/InitializePasses.h"
for where in-tree pass initializers are declared.