[llvm-dev] writing a pass, questions

[Preston Briggs via llvm-dev]

I'm moving a couple of dynamically loaded passes
from an older version of LLVM to a newer one.
I fixed various small compilation errors, and things compile now,
but the resulting .so won't load without error.

So I re-read the manual (Writing an LLVM Pass) and tried the
first example, Hello.cpp which produces LLVMHello.cpp
The code's already there in the source tree and it builds
and loads correctly. So I tried copying the directory
and doing a little editing. It builds but again fails to load.

Here's what I type

opt -load LLVMZap.so -help


and here's what I see

Error opening 'LLVMZap.so':
/home/briggs/llvm-cilk/new_install/bin/../lib/LLVMZap.so: undefined symbol:
_ZNK4llvm12FunctionPass17createPrinterPassERNS_11raw_ostreamERKNSt3__112basic_stringIcNS3_11char_traitsIcEENS3_9allocatorIcEEEE
  -load request ignored.


The error message is quite similar to what I see when I'm experimenting
with my old pass.

Any ideas?

Here's the contents of CMake.txt

# If we don't need RTTI or EH, there's no reason to export anything
# from the hello plugin.
if( NOT LLVM_REQUIRES_RTTI )
  if( NOT LLVM_REQUIRES_EH )
    set(LLVM_EXPORTED_SYMBOL_FILE ${CMAKE_CURRENT_SOURCE_DIR}/Zap.exports)
  endif()
endif()

add_llvm_loadable_module( LLVMZap
  Zap.cpp

  DEPENDS
  intrinsics_gen
  PLUGIN_TOOL
  opt
  )


And the contents of Zap.cpp


#include "llvm/IR/Function.h"
#include "llvm/Pass.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

namespace {
  struct Zap : public FunctionPass {
    static char ID; // Pass identification, replacement for typeid
    Zap() : FunctionPass(ID) {}

    bool runOnFunction(Function &F) override {
      errs() << "Zap! ";
      errs().write_escaped(F.getName()) << '\n';
      return false;
    }
  };
}

char Zap::ID = 0;
static RegisterPass<Zap> X("zap", "Zap Pass");


Thanks,
Preston
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