replace_ctors_repro

CMakeLists.txt

cmake_minimum_required(VERSION 3.4)
project(repro)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++1z -fPIC -fno-exceptions -fno-rtti -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wcovered-switch-default -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -Werror=date-time")
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -fno-omit-frame-pointer -fsanitize=undefined")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3")

include_directories(~/Projects/llvm/include
                    ~/Projects/llvm/tools/clang/include
                    ~/Projects/build_llvm/include
                    ~/Projects/build_llvm/tools/clang/include)

link_directories(~/Projects/build_llvm/lib)

add_library(repro SHARED repro.cpp)

repro.cpp

#include "clang/AST/AST.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/FrontendPluginRegistry.h"
#include "clang/Sema/Sema.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;
using namespace clang;

namespace {

class Repro : public ASTConsumer {
  CompilerInstance &Instance;
  std::set<std::string> ParsedTemplates;

public:
  Repro(CompilerInstance &Instance, std::set<std::string> ParsedTemplates)
      : Instance(Instance), ParsedTemplates(ParsedTemplates) {}

  bool HandleTopLevelDecl(DeclGroupRef DG) override {
    for (auto it = DG.begin(), e = DG.end(); it != e; ++it) {
      if (auto *VD = dyn_cast<VarDecl>(*it)) {
        if (VD->getName() == "c")
          ChangeCtor(VD);
      }
    }

    return true;
  }

private:
  void ChangeCtor(VarDecl *VD) {
    VD->dump();

    auto &Sema = Instance.getSema();
    auto &Context = Sema.getASTContext();
    auto Loc = VD->getSourceRange().getBegin();
    auto VarQT = VD->getType();

    auto *Zero = clang::IntegerLiteral::Create(Context, llvm::APInt(32, 0),
                                               Context.IntTy, Loc);

    auto *RDecl = VarQT->getAsCXXRecordDecl();
    CXXConstructorDecl *Ctor = nullptr;
    for (auto *CD : RDecl->ctors())
      if (CD->getNumParams() == 2)
        Ctor = CD;

    Expr *Params[] = {Zero, Zero};
    auto *ConstructExpr = CXXConstructExpr::Create(
        Context, VarQT, Loc, Ctor, false, Params, true, true, false, false,
        CXXConstructExpr::CK_Complete, VD->getSourceRange());

    ConstructExpr->dump();
    VD->setInit(ConstructExpr);
    VD->dump();
  }
};

class ReproAction : public PluginASTAction {
  std::set<std::string> ParsedTemplates;

protected:
  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                 llvm::StringRef) override {
    return llvm::make_unique<Repro>(CI, ParsedTemplates);
  }

  bool ParseArgs(const CompilerInstance &,
                 const std::vector<std::string> &) override {
    return true;
  }

  ActionType getActionType() override { return AddBeforeMainAction; }
};
}

static FrontendPluginRegistry::Add<ReproAction> X("repro", "");

test.cpp

template <typename> struct C {
  C() {}
  C(int, int) {}
};

C<void> c = {};
//C<void> d = {0, 0};

int main() {}