Bisect clang

tools/clang/rewrite_scoped_refptr/RewriteScopedRefptr.cpp

+// Copyright (c) 2013 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.
+//
+// This implements a Clang tool to rewrite all instances of
+// scoped_refptr<T>'s implicit cast to T (operator T*) to an explicit call to
+// the .get() method.
+
+#include <assert.h>
+#include <algorithm>
+#include <memory>
+#include <string>
+
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/support/TargetSelect.h"
+
+using namespace clang::ast_matchers;
+using clang::tooling::CommonOptionsParser;
+using clang::tooling::Replacement;
+using clang::tooling::Replacements;
+using llvm::StringRef;
+
+namespace clang {
+namespace ast_matchers {
+
+const internal::VariadicDynCastAllOfMatcher<Decl, CXXConversionDecl>
+    conversionDecl;
+
+AST_MATCHER(QualType, isBoolean) {
+  return Node->isBooleanType();
+}
+
+}  // namespace ast_matchers
+}  // namespace clang
+
+namespace {
+
+// Returns true if expr needs to be put in parens (eg: when it is an operator
+// syntactically).
+bool NeedsParens(const clang::Expr* expr) {
+  if (llvm::dyn_cast<clang::UnaryOperator>(expr) ||
+      llvm::dyn_cast<clang::BinaryOperator>(expr) ||
+      llvm::dyn_cast<clang::ConditionalOperator>(expr)) {
+    return true;
+  }
+  // Calls to an overloaded operator also need parens, except for foo(...) and
+  // foo[...] expressions.
+  if (const clang::CXXOperatorCallExpr* op =
+          llvm::dyn_cast<clang::CXXOperatorCallExpr>(expr)) {
+    return op->getOperator() != clang::OO_Call &&
+           op->getOperator() != clang::OO_Subscript;
+  }
+  return false;
+}
+
+Replacement RewriteImplicitToExplicitConversion(
+    const MatchFinder::MatchResult& result,
+    const clang::Expr* expr) {
+  clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(
+      result.SourceManager->getSpellingLoc(expr->getLocStart()),
+      result.SourceManager->getSpellingLoc(expr->getLocEnd()));
+  assert(range.isValid() && "Invalid range!");
+
+  // Handle cases where an implicit cast is being done by dereferencing a
+  // pointer to a scoped_refptr<> (sadly, it happens...)
+  //
+  // This rewrites both "*foo" and "*(foo)" as "foo->get()".
+  if (const clang::UnaryOperator* op =
+          llvm::dyn_cast<clang::UnaryOperator>(expr)) {
+    if (op->getOpcode() == clang::UO_Deref) {
+      const clang::Expr* const sub_expr =
+          op->getSubExpr()->IgnoreParenImpCasts();
+      clang::CharSourceRange sub_expr_range =
+          clang::CharSourceRange::getTokenRange(
+              result.SourceManager->getSpellingLoc(sub_expr->getLocStart()),
+              result.SourceManager->getSpellingLoc(sub_expr->getLocEnd()));
+      assert(sub_expr_range.isValid() && "Invalid subexpression range!");
+
+      std::string inner_text = clang::Lexer::getSourceText(
+          sub_expr_range, *result.SourceManager, result.Context->getLangOpts());
+      assert(!inner_text.empty() && "No text for subexpression!");
+      if (NeedsParens(sub_expr)) {
+        inner_text.insert(0, "(");
+        inner_text.append(")");
+      }
+      inner_text.append("->get()");
+      return Replacement(*result.SourceManager, range, inner_text);
+    }
+  }
+
+  std::string text = clang::Lexer::getSourceText(
+      range, *result.SourceManager, result.Context->getLangOpts());
+  assert(!text.empty() && "No text for expression!");
+
+  // Unwrap any temporaries - for example, custom iterators that return
+  // scoped_refptr<T> as part of operator*. Any such iterators should also
+  // be declaring a scoped_refptr<T>* operator->, per C++03 24.4.1.1 (Table 72)
+  if (const clang::CXXBindTemporaryExpr* op =
+          llvm::dyn_cast<clang::CXXBindTemporaryExpr>(expr)) {
+    expr = op->getSubExpr();
+  }
+
+  // Handle iterators (which are operator* calls, followed by implicit
+  // conversions) by rewriting *it as it->get()
+  if (const clang::CXXOperatorCallExpr* op =
+          llvm::dyn_cast<clang::CXXOperatorCallExpr>(expr)) {
+    if (op->getOperator() == clang::OO_Star) {
+      // Note that this doesn't rewrite **it correctly, since it should be
+      // rewritten using parens, e.g. (*it)->get(). However, this shouldn't
+      // happen frequently, if at all, since it would likely indicate code is
+      // storing pointers to a scoped_refptr in a container.
+      text.erase(0, 1);
+      text.append("->get()");
+      return Replacement(*result.SourceManager, range, text);
+    }
+  }
+
+  // The only remaining calls should be non-dereferencing calls (eg: member
+  // calls), so a simple ".get()" appending should suffice.
+  if (NeedsParens(expr)) {
+    text.insert(0, "(");
+    text.append(")");
+  }
+  text.append(".get()");
+  return Replacement(*result.SourceManager, range, text);
+}
+
+Replacement RewriteRawPtrToScopedRefptr(const MatchFinder::MatchResult& result,
+                                        clang::SourceLocation begin,
+                                        clang::SourceLocation end) {
+  clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(
+      result.SourceManager->getSpellingLoc(begin),
+      result.SourceManager->getSpellingLoc(end));
+  assert(range.isValid() && "Invalid range!");
+
+  std::string text = clang::Lexer::getSourceText(
+      range, *result.SourceManager, result.Context->getLangOpts());
+  text.erase(text.rfind('*'));
+
+  std::string replacement_text("scoped_refptr<");
+  replacement_text += text;
+  replacement_text += ">";
+
+  return Replacement(*result.SourceManager, range, replacement_text);
+}
+
+class GetRewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  explicit GetRewriterCallback(Replacements* replacements)
+      : replacements_(replacements) {}
+  virtual void run(const MatchFinder::MatchResult& result) override;
+
+ private:
+  Replacements* const replacements_;
+};
+
+void GetRewriterCallback::run(const MatchFinder::MatchResult& result) {
+  const clang::Expr* arg = result.Nodes.getNodeAs<clang::Expr>("arg");
+  assert(arg && "Unexpected match! No Expr captured!");
+  replacements_->insert(RewriteImplicitToExplicitConversion(result, arg));
+}
+
+class VarRewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  explicit VarRewriterCallback(Replacements* replacements)
+      : replacements_(replacements) {}
+  virtual void run(const MatchFinder::MatchResult& result) override;
+
+ private:
+  Replacements* const replacements_;
+};
+
+void VarRewriterCallback::run(const MatchFinder::MatchResult& result) {
+  const clang::DeclaratorDecl* const var_decl =
+      result.Nodes.getNodeAs<clang::DeclaratorDecl>("var");
+  assert(var_decl && "Unexpected match! No VarDecl captured!");
+
+  const clang::TypeSourceInfo* tsi = var_decl->getTypeSourceInfo();
+
+  // TODO(dcheng): This mishandles a case where a variable has multiple
+  // declarations, e.g.:
+  //
+  // in .h:
+  // Foo* my_global_magical_foo;
+  //
+  // in .cc:
+  // Foo* my_global_magical_foo = CreateFoo();
+  //
+  // In this case, it will only rewrite the .cc definition. Oh well. This should
+  // be rare enough that these cases can be manually handled, since the style
+  // guide prohibits globals of non-POD type.
+  replacements_->insert(RewriteRawPtrToScopedRefptr(
+      result, tsi->getTypeLoc().getBeginLoc(), tsi->getTypeLoc().getEndLoc()));
+}
+
+class FunctionRewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  explicit FunctionRewriterCallback(Replacements* replacements)
+      : replacements_(replacements) {}
+  virtual void run(const MatchFinder::MatchResult& result) override;
+
+ private:
+  Replacements* const replacements_;
+};
+
+void FunctionRewriterCallback::run(const MatchFinder::MatchResult& result) {
+  const clang::FunctionDecl* const function_decl =
+      result.Nodes.getNodeAs<clang::FunctionDecl>("fn");
+  assert(function_decl && "Unexpected match! No FunctionDecl captured!");
+
+  // If matched against an implicit conversion to a DeclRefExpr, make sure the
+  // referenced declaration is of class type, e.g. the tool skips trying to
+  // chase pointers/references to determine if the pointee is a scoped_refptr<T>
+  // with local storage. Instead, let a human manually handle those cases.
+  const clang::VarDecl* const var_decl =
+      result.Nodes.getNodeAs<clang::VarDecl>("var");
+  if (var_decl && !var_decl->getTypeSourceInfo()->getType()->isClassType()) {
+    return;
+  }
+
+  for (clang::FunctionDecl* f : function_decl->redecls()) {
+    clang::SourceRange range = f->getReturnTypeSourceRange();
+    replacements_->insert(
+        RewriteRawPtrToScopedRefptr(result, range.getBegin(), range.getEnd()));
+  }
+}
+
+class MacroRewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  explicit MacroRewriterCallback(Replacements* replacements)
+      : replacements_(replacements) {}
+  virtual void run(const MatchFinder::MatchResult& result) override;
+
+ private:
+  Replacements* const replacements_;
+};
+
+void MacroRewriterCallback::run(const MatchFinder::MatchResult& result) {
+  const clang::Expr* const expr = result.Nodes.getNodeAs<clang::Expr>("expr");
+  assert(expr && "Unexpected match! No Expr captured!");
+  replacements_->insert(RewriteImplicitToExplicitConversion(result, expr));
+}
+
+}  // namespace
+
+static llvm::cl::extrahelp common_help(CommonOptionsParser::HelpMessage);
+
+int main(int argc, const char* argv[]) {
+  // TODO(dcheng): Clang tooling should do this itself.
+  // http://llvm.org/bugs/show_bug.cgi?id=21627
+  llvm::InitializeNativeTarget();
+  llvm::InitializeNativeTargetAsmParser();
+  llvm::cl::OptionCategory category("Remove scoped_refptr conversions");
+  CommonOptionsParser options(argc, argv, category);
+  clang::tooling::ClangTool tool(options.getCompilations(),
+                                 options.getSourcePathList());
+
+  MatchFinder match_finder;
+  Replacements replacements;
+
+  auto is_scoped_refptr = recordDecl(isSameOrDerivedFrom("::scoped_refptr"),
+                                     isTemplateInstantiation());
+
+  // Finds all calls to conversion operator member function. This catches calls
+  // to "operator T*", "operator Testable", and "operator bool" equally.
+  auto base_matcher = memberCallExpr(thisPointerType(is_scoped_refptr),
+                                     callee(conversionDecl()),
+                                     on(id("arg", expr())));
+
+  // The heuristic for whether or not converting a temporary is 'unsafe'. An
+  // unsafe conversion is one where a temporary scoped_refptr<T> is converted to
+  // another type. The matcher provides an exception for a temporary
+  // scoped_refptr that is the result of an operator call. In this case, assume
+  // that it's the result of an iterator dereference, and the container itself
+  // retains the necessary reference, since this is a common idiom to see in
+  // loop bodies.
+  auto is_unsafe_temporary_conversion =
+      on(bindTemporaryExpr(unless(has(operatorCallExpr()))));
+
+  // Returning a scoped_refptr<T> as a T* is considered unsafe if either are
+  // true:
+  // - The scoped_refptr<T> is a temporary.
+  // - The scoped_refptr<T> has local lifetime.
+  auto returned_as_raw_ptr = hasParent(
+      returnStmt(hasAncestor(id("fn", functionDecl(returns(pointerType()))))));
+  // This matcher intentionally matches more than it should. For example, this
+  // will match:
+  //   scoped_refptr<Foo>& foo = some_other_foo;
+  //   return foo;
+  // The matcher callback filters out VarDecls that aren't a scoped_refptr<T>,
+  // so those cases can be manually handled.
+  auto is_local_variable =
+      on(declRefExpr(to(id("var", varDecl(hasLocalStorage())))));
+  auto is_unsafe_return =
+      anyOf(allOf(hasParent(implicitCastExpr(returned_as_raw_ptr)),
+                  is_local_variable),
+            allOf(hasParent(implicitCastExpr(
+                      hasParent(exprWithCleanups(returned_as_raw_ptr)))),
+                  is_unsafe_temporary_conversion));
+
+  // This catches both user-defined conversions (eg: "operator bool") and
+  // standard conversion sequence (C++03 13.3.3.1.1), such as converting a
+  // pointer to a bool.
+  auto implicit_to_bool =
+      implicitCastExpr(hasImplicitDestinationType(isBoolean()));
+
+  // Avoid converting calls to of "operator Testable" -> "bool" and calls of
+  // "operator T*" -> "bool".
+  auto bool_conversion_matcher = hasParent(
+      expr(anyOf(implicit_to_bool, expr(hasParent(implicit_to_bool)))));
+
+  auto is_logging_helper =
+      functionDecl(anyOf(hasName("CheckEQImpl"), hasName("CheckNEImpl")));
+  auto is_gtest_helper = functionDecl(
+      anyOf(methodDecl(ofClass(recordDecl(isSameOrDerivedFrom(
+                           hasName("::testing::internal::EqHelper")))),
+                       hasName("Compare")),
+            hasName("::testing::internal::CmpHelperNE")));
+  auto is_gtest_assertion_result_ctor = constructorDecl(ofClass(
+      recordDecl(isSameOrDerivedFrom(hasName("::testing::AssertionResult")))));
+
+  // Find all calls to an operator overload that are 'safe'.
+  //
+  // All bool conversions will be handled with the Testable trick, but that
+  // can only be used once "operator T*" is removed, since otherwise it leaves
+  // the call ambiguous.
+  GetRewriterCallback get_callback(&replacements);
+  match_finder.addMatcher(
+      memberCallExpr(
+          base_matcher,
+          // Excluded since the conversion may be unsafe.
+          unless(anyOf(is_unsafe_temporary_conversion, is_unsafe_return)),
+          // Excluded since the conversion occurs inside a helper function that
+          // the macro wraps. Letting this callback handle the rewrite would
+          // result in an incorrect replacement that changes the helper function
+          // itself. Instead, the right replacement is to rewrite the macro's
+          // arguments.
+          unless(hasAncestor(decl(anyOf(is_logging_helper,
+                                        is_gtest_helper,
+                                        is_gtest_assertion_result_ctor))))),
+      &get_callback);
+
+  // Find temporary scoped_refptr<T>'s being unsafely assigned to a T*.
+  VarRewriterCallback var_callback(&replacements);
+  auto initialized_with_temporary = ignoringImpCasts(exprWithCleanups(
+      has(memberCallExpr(base_matcher, is_unsafe_temporary_conversion))));
+  match_finder.addMatcher(id("var",
+                             varDecl(hasInitializer(initialized_with_temporary),
+                                     hasType(pointerType()))),
+                          &var_callback);
+  match_finder.addMatcher(
+      constructorDecl(forEachConstructorInitializer(
+          allOf(withInitializer(initialized_with_temporary),
+                forField(id("var", fieldDecl(hasType(pointerType()))))))),
+      &var_callback);
+
+  // Rewrite functions that unsafely turn a scoped_refptr<T> into a T* when
+  // returning a value.
+  FunctionRewriterCallback fn_callback(&replacements);
+  match_finder.addMatcher(memberCallExpr(base_matcher, is_unsafe_return),
+                          &fn_callback);
+
+  // Rewrite logging / gtest expressions that result in an implicit conversion.
+  // Luckily, the matchers don't need to handle the case where one of the macro
+  // arguments is NULL, such as:
+  // CHECK_EQ(my_scoped_refptr, NULL)
+  // because it simply doesn't compile--since NULL is actually of integral type,
+  // this doesn't trigger scoped_refptr<T>'s implicit conversion. Since there is
+  // no comparison overload for scoped_refptr<T> and int, this fails to compile.
+  MacroRewriterCallback macro_callback(&replacements);
+  // CHECK_EQ/CHECK_NE helpers.
+  match_finder.addMatcher(
+      callExpr(callee(is_logging_helper),
+               argumentCountIs(3),
+               hasAnyArgument(id("expr", expr(hasType(is_scoped_refptr)))),
+               hasAnyArgument(hasType(pointerType())),
+               hasArgument(2, stringLiteral())),
+      &macro_callback);
+  // ASSERT_EQ/ASSERT_NE/EXPECT_EQ/EXPECT_EQ, which use the same underlying
+  // helper functions. Even though gtest has special handling for pointer to
+  // NULL comparisons, it doesn't trigger in this case, so no special handling
+  // is needed for the replacements.
+  match_finder.addMatcher(
+      callExpr(callee(is_gtest_helper),
+               argumentCountIs(4),
+               hasArgument(0, stringLiteral()),
+               hasArgument(1, stringLiteral()),
+               hasAnyArgument(id("expr", expr(hasType(is_scoped_refptr)))),
+               hasAnyArgument(hasType(pointerType()))),
+      &macro_callback);
+  // ASSERT_TRUE/EXPECT_TRUE helpers. Note that this matcher doesn't need to
+  // handle ASSERT_FALSE/EXPECT_FALSE, because it gets coerced to bool before
+  // being passed as an argument to AssertionResult's constructor. As a result,
+  // GetRewriterCallback handles this case properly since the conversion isn't
+  // hidden inside AssertionResult, and the generated replacement properly
+  // rewrites the macro argument.
+  // However, the tool does need to handle the _TRUE counterparts, since the
+  // conversion occurs inside the constructor in those cases.
+  match_finder.addMatcher(
+      constructExpr(
+          argumentCountIs(2),
+          hasArgument(0, id("expr", expr(hasType(is_scoped_refptr)))),
+          hasDeclaration(is_gtest_assertion_result_ctor)),
+      &macro_callback);
+
+  std::unique_ptr<clang::tooling::FrontendActionFactory> factory =
+      clang::tooling::newFrontendActionFactory(&match_finder);
+  int result = tool.run(factory.get());
+  if (result != 0)
+    return result;
+
+  // Serialization format is documented in tools/clang/scripts/run_tool.py
+  llvm::outs() << "==== BEGIN EDITS ====\n";
+  for (const auto& r : replacements) {
+    std::string replacement_text = r.getReplacementText().str();
+    std::replace(replacement_text.begin(), replacement_text.end(), '\n', '\0');
+    llvm::outs() << "r:::" << r.getFilePath() << ":::" << r.getOffset() << ":::"
+                 << r.getLength() << ":::" << replacement_text << "\n";
+  }
+  llvm::outs() << "==== END EDITS ====\n";
+
+  return 0;
+}