1 files changed, 152 insertions, 0 deletions
diff --git a/build/clang-plugin/RefCountedInsideLambdaChecker.cpp b/build/clang-plugin/RefCountedInsideLambdaChecker.cpp
new file mode 100644
index 0000000000..8a95b761de
--- /dev/null
+++ b/build/clang-plugin/RefCountedInsideLambdaChecker.cpp
@@ -0,0 +1,152 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RefCountedInsideLambdaChecker.h"
+#include "CustomMatchers.h"
+
+RefCountedMap RefCountedClasses;
+
+void RefCountedInsideLambdaChecker::registerMatchers(MatchFinder *AstMatcher) {
+  // We want to reject any code which captures a pointer to an object of a
+  // refcounted type, and then lets that value escape. As a primitive analysis,
+  // we reject any occurances of the lambda as a template parameter to a class
+  // (which could allow it to escape), as well as any presence of such a lambda
+  // in a return value (either from lambdas, or in c++14, auto functions).
+  //
+  // We check these lambdas' capture lists for raw pointers to refcounted types.
+  AstMatcher->addMatcher(functionDecl(returns(recordType(hasDeclaration(
+                             cxxRecordDecl(isLambdaDecl()).bind("decl"))))),
+                         this);
+  AstMatcher->addMatcher(lambdaExpr().bind("lambdaExpr"), this);
+  AstMatcher->addMatcher(
+      classTemplateSpecializationDecl(
+          hasAnyTemplateArgument(refersToType(recordType(
+              hasDeclaration(cxxRecordDecl(isLambdaDecl()).bind("decl")))))),
+      this);
+}
+
+void RefCountedInsideLambdaChecker::emitDiagnostics(SourceLocation Loc,
+                                                    StringRef Name,
+                                                    QualType Type) {
+  diag(Loc,
+       "Refcounted variable '%0' of type %1 cannot be captured by a lambda",
+       DiagnosticIDs::Error)
+      << Name << Type;
+  diag(Loc, "Please consider using a smart pointer", DiagnosticIDs::Note);
+}
+
+void RefCountedInsideLambdaChecker::check(
+    const MatchFinder::MatchResult &Result) {
+  static DenseSet<const CXXRecordDecl *> CheckedDecls;
+
+  const CXXRecordDecl *Lambda = Result.Nodes.getNodeAs<CXXRecordDecl>("decl");
+
+  if (const LambdaExpr *OuterLambda =
+          Result.Nodes.getNodeAs<LambdaExpr>("lambdaExpr")) {
+    const CXXMethodDecl *OpCall = OuterLambda->getCallOperator();
+    QualType ReturnTy = OpCall->getReturnType();
+    if (const CXXRecordDecl *Record = ReturnTy->getAsCXXRecordDecl()) {
+      Lambda = Record;
+    }
+  }
+
+  if (!Lambda || !Lambda->isLambda()) {
+    return;
+  }
+
+  // Don't report errors on the same declarations more than once.
+  if (CheckedDecls.count(Lambda)) {
+    return;
+  }
+  CheckedDecls.insert(Lambda);
+
+  bool StrongRefToThisCaptured = false;
+
+  for (const LambdaCapture &Capture : Lambda->captures()) {
+    // Check if any of the captures are ByRef. If they are, we have nothing to
+    // report, as it's OK to capture raw pointers to refcounted objects so long
+    // as the Lambda doesn't escape the current scope, which is required by
+    // ByRef captures already.
+    if (Capture.getCaptureKind() == LCK_ByRef) {
+      return;
+    }
+
+    // Check if this capture is byvalue, and captures a strong reference to
+    // this.
+    // XXX: Do we want to make sure that this type which we are capturing is a
+    // "Smart Pointer" somehow?
+    if (!StrongRefToThisCaptured && Capture.capturesVariable() &&
+        Capture.getCaptureKind() == LCK_ByCopy) {
+      const VarDecl *Var = Capture.getCapturedVar();
+      if (Var->hasInit()) {
+        const Stmt *Init = Var->getInit();
+
+        // Ignore single argument constructors, and trivial nodes.
+        while (true) {
+          auto NewInit = IgnoreTrivials(Init);
+          if (auto ConstructExpr = dyn_cast<CXXConstructExpr>(NewInit)) {
+            if (ConstructExpr->getNumArgs() == 1) {
+              NewInit = ConstructExpr->getArg(0);
+            }
+          }
+          if (Init == NewInit) {
+            break;
+          }
+          Init = NewInit;
+        }
+
+        if (isa<CXXThisExpr>(Init)) {
+          StrongRefToThisCaptured = true;
+        }
+      }
+    }
+  }
+
+  // Now we can go through and produce errors for any captured variables or this
+  // pointers.
+  for (const LambdaCapture &Capture : Lambda->captures()) {
+    if (Capture.capturesVariable()) {
+      QualType Pointee = Capture.getCapturedVar()->getType()->getPointeeType();
+
+      if (!Pointee.isNull() && isClassRefCounted(Pointee)) {
+        emitDiagnostics(Capture.getLocation(),
+                        Capture.getCapturedVar()->getName(), Pointee);
+        return;
+      }
+    }
+
+    // The situation with captures of `this` is more complex. All captures of
+    // `this` look the same-ish (they are LCK_This). We want to complain about
+    // captures of `this` where `this` is a refcounted type, and the capture is
+    // actually used in the body of the lambda (if the capture isn't used, then
+    // we don't care, because it's only being captured in order to give access
+    // to private methods).
+    //
+    // In addition, we don't complain about this, even if it is used, if it was
+    // captured implicitly when the LambdaCaptureDefault was LCD_ByRef, as that
+    // expresses the intent that the lambda won't leave the enclosing scope.
+    bool ImplicitByRefDefaultedCapture =
+        Capture.isImplicit() && Lambda->getLambdaCaptureDefault() == LCD_ByRef;
+    if (Capture.capturesThis() && !ImplicitByRefDefaultedCapture &&
+        !StrongRefToThisCaptured) {
+      ThisVisitor V(*this);
+      bool NotAborted = V.TraverseDecl(
+          const_cast<CXXMethodDecl *>(Lambda->getLambdaCallOperator()));
+      if (!NotAborted) {
+        return;
+      }
+    }
+  }
+}
+
+bool RefCountedInsideLambdaChecker::ThisVisitor::VisitCXXThisExpr(
+    CXXThisExpr *This) {
+  QualType Pointee = This->getType()->getPointeeType();
+  if (!Pointee.isNull() && isClassRefCounted(Pointee)) {
+    Checker.emitDiagnostics(This->getBeginLoc(), "this", Pointee);
+    return false;
+  }
+
+  return true;
+}