[cfe-dev] Plugin: Rewriter does not work?

[Marcel Schaible via cfe-dev]

Hi,

in my clang plugin I want to rewrite certain parts of the translation 
unit. In the MyVisitor I'll setup a rewriter and try to replace for e.g. 
the name of a function decl:

TheRewriter.ReplaceText(funcDecl->getLocation(), funcName.length(), 
"myreturn");

This code is excecuted but the chnage is not visible in the generated 
assmebler file.

Any idea what I am doing wrong?

Thanks

Marcel

<---snippet--->

Rewriter    TheRewriter;

namespace {

     class MyVisitor : public RecursiveASTVisitor<MyVisitor> {
     private:
         ASTContext *astContext;

     public:
         explicit MyVisitor(CompilerInstance *CI) : 
m_diag(CI->getDiagnostics()),
             astContext(&(CI->getASTContext()))
         {
TheRewriter.setSourceMgr(astContext->getSourceManager(), 
astContext->getLangOpts());
         }

         bool VisitFunctionDecl(const FunctionDecl *funcDecl) {
             string funcName = 
funcDecl->getNameInfo().getName().getAsString();
             if (funcName == "return_fourtytwo") {
TheRewriter.ReplaceText(funcDecl->getLocation(), funcName.length(), 
"myreturn");
                 errs() << "Rewrote function def: " << funcName << "\n";
             }

     private:
         DiagnosticsEngine &m_diag;
     };

     class FuncDeclConsumer : public ASTConsumer {
     public:
         explicit FuncDeclConsumer(CompilerInstance *CI)
             : m_visitor(MyVisitor(CI)) {}

         // Called by the parser for each top-level declaration group.
         // Returns true to continue parsing, or false to abort parsing.
         virtual bool HandleTopLevelDecl(DeclGroupRef dg) override {
             for (Decl *decl : dg) {
                 m_visitor.TraverseDecl(decl);
             }
             return true;
         }

     private:
         MyVisitor m_visitor;
     };

     class MyInstrumentation : public PluginASTAction {
     protected:
         std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance 
&ci,
             llvm::StringRef) override {
             return llvm::make_unique<FuncDeclConsumer>(&ci);
         }

         PluginASTAction::ActionType getActionType() override {
             return AddAfterMainAction;
         }
     };
} // end namespace

static FrontendPluginRegistry::Add<MyInstrumentation>
X("check-parameter-names", "check for parameter names mismatch");