Clang plugin that rewrites PostTask(_, NewRunnableMethod(...)) to PostTask(_, base::Bind(...));

tools/clang/BindMigrate/PostTaskTransform.cpp

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "PostTaskTransform.h"
+
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/Rewrite/Rewriter.h"
+
+#include "DiagnosticEmitter.h"
+
+using namespace std;
+
+namespace clang {
+
+PostTaskTransform::PostTaskTransform(ASTContext* context, Rewriter* rewriter,
+                                     DiagnosticEmitter* emitter)
+    : context_(context), rewriter_(rewriter), error_emitter_(emitter) {
+  interesting_classes_.insert("MessageLoop");
+  interesting_classes_.insert("MessageLoopProxy");
+}
+
+bool PostTaskTransform::WouldTransformStmt(Stmt* statement) {
+  return IsPostTaskNRMExpr(statement);
+}
+
+void PostTaskTransform::TransformStmt(Stmt* statement) {
+  if (!IsPostTaskNRMExpr(statement)) return;
+
+  // Catch the MessageLoop and MessageLoopProxy calls.
+  CXXMemberCallExpr* mce = dyn_cast<CXXMemberCallExpr>(statement);
+  RewriteIfNewRunnableSomething(mce->getArgs()[1]);
+}
+
+bool PostTaskTransform::IsPostTaskNRMExpr(Stmt* statement) {
+  CXXMemberCallExpr* call = dyn_cast_or_null<CXXMemberCallExpr>(statement);
+  if (!call) return false;
+  CXXMethodDecl* method_decl = call->getMethodDecl();
+  if (!method_decl) return false;
+  method_decl = method_decl->getCanonicalDecl();
+  if ("PostTask" != method_decl->getNameAsString()) {
+    return false;
+  }
+
+  string classname = method_decl->getThisType(*context_)
+      .getBaseTypeIdentifier()->getName();
+
+  if (interesting_classes_.find(classname) == interesting_classes_.end())
+    return false;
+
+  if (call->getNumArgs() < 2) {
+    error_emitter_->EmitError(
+        statement->getLocStart(),
+        "PostTask with less than 2 args?!  Inconceivable!");
+    return false;
+  }
+
+  // Check that PostTask second arg is actually the ::NewRunnableMethod() call.
+  CallExpr* nrm_ce = dyn_cast<CallExpr>(call->getArgs()[1]);
+  if (!nrm_ce) return false;
+  if (dyn_cast<CXXMemberCallExpr>(nrm_ce)) return false;
+  FunctionDecl *nrm_fd = nrm_ce->getDirectCallee();
+  if (!nrm_fd) return false;
+  std::string nrm_function_name =
+      nrm_fd->getNameInfo().getName().getAsIdentifierInfo()->getName();
+  if ("NewRunnableMethod" != nrm_function_name) {
+    return false;
+  }
+
+  if (nrm_ce->getNumArgs() < 2) {
+    error_emitter_->EmitWarning(
+        nrm_ce->getLocStart(),
+        "NewRunnableMethod with less than 2 args?!  Inconceivable!");
+    return false;
+  }
+
+  return true;
+}
+
+static bool NoAddrefRelease(const CXXRecordDecl *record, void *user_data) {
+  bool found_addref = false;
+  bool found_release = false;
+
+  for (CXXRecordDecl::method_iterator it = record->method_begin(),
+       end = record->method_end(); it != end; ++it) {
+    if (it->getAccess() == AS_public) {
+      found_addref |= "AddRef" == it->getNameAsString();
+      found_release |= "Release"  == it->getNameAsString();
+    }
+  }
+
+  return !(found_addref && found_release);
+}
+
+bool PostTaskTransform::IsRefcountedType(QualType type) {
+  CXXRecordDecl* record = type->getAsCXXRecordDecl();
+  return !(NoAddrefRelease(record, NULL) &&
+      record->forallBases(&NoAddrefRelease, NULL, true));
+}
+
+bool PostTaskTransform::RewriteIfNewRunnableSomething(Expr* post_task_arg) {
+  // Skip any implicit conversions and any casts. We wantz the function!!
+  post_task_arg = post_task_arg->IgnoreImplicit()->IgnoreParenCasts();
+
+  CallExpr* ce = dyn_cast<CallExpr>(post_task_arg);
+  if (!ce) return false;
+  FunctionDecl *fd = ce->getDirectCallee();
+  if (!fd) return false;
+
+  // Okay, here's where it gets fun.  We need to
+  // (1) replace the NRM identifier text with base::Bind.
+  // (2) Swap positions of the first two arguments.
+  // (3) If we're calling a method, and the class is not refcounted, then
+  //     a DISABLE_RUNNABLE_METHOD_REFCOUNT or similar must have been used
+  //     to disable refcounting.  Insert a base::Unretained().
+
+  // NewRunnableMethod -> base::Bind
+  bool failure = rewriter_->ReplaceText(
+      ce->getCallee()->getSourceRange(), "base::Bind");
+
+  Expr* arg1 = ce->getArgs()[0];
+  Expr* arg2 = ce->getArgs()[1];
+
+
+  // Swap args, and add unretained to the object if needed.
+  failure |= rewriter_->ReplaceStmt(arg1, arg2);
+  if (arg2->getType()->isMemberFunctionPointerType() &&
+      arg1->getType()->isPointerType() &&
+      arg1->getType()->getPointeeType()->isStructureOrClassType() &&
+      !IsRefcountedType(arg1->getType()->getPointeeType())) {
+    // The rewriter works in the context of the soruce buffer.  Though it
+    // tries to be smart about mapping the source location into the
+    // destination over multiple rewrites, it can get confused if you try
+    // to modify the same region of text multiple times.  Doing things in
+    // order from "left to right" seems to keep the Rewritter happier.
+    //
+    // TODO(ajwong): See if the ARCMigrate source transaction system that
+    // batches and combines modificaitons to be applied at the end can
+    // be generalized and reused here.
+    std::string unretained_arg("base::Unretained(");
+    unretained_arg += rewriter_->ConvertToString(arg1);
+    unretained_arg += ")";
+    failure |= rewriter_->ReplaceText(arg2->getSourceRange(), unretained_arg);
+  } else {
+    failure |= rewriter_->ReplaceStmt(arg2, arg1);
+  }
+  return failure;
+}
+
+}  // namespace clang