1 files changed, 35 insertions, 0 deletions
diff --git a/build/clang-plugin/KnownLiveChecker.cpp b/build/clang-plugin/KnownLiveChecker.cpp
new file mode 100644
index 0000000000..be0c3739ec
--- /dev/null
+++ b/build/clang-plugin/KnownLiveChecker.cpp
@@ -0,0 +1,35 @@
+/* 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 "KnownLiveChecker.h"
+#include "CustomMatchers.h"
+
+void KnownLiveChecker::registerMatchers(MatchFinder *AstMatcher) {
+  // Note that this cannot catch mutations after pass-by-reference, and thus no
+  // error for cycle collection macros.
+
+  auto KnownLiveLHS = hasLHS(memberExpr(hasKnownLiveAnnotation()).bind("lhs"));
+  auto ForGeneralFunctions = forFunction(
+      functionDecl(unless(anyOf(cxxConstructorDecl(), cxxDestructorDecl())))
+          .bind("func"));
+
+  auto Matcher =
+      allOf(isAssignmentOperator(), KnownLiveLHS, ForGeneralFunctions);
+
+  AstMatcher->addMatcher(binaryOperator(Matcher), this);
+  AstMatcher->addMatcher(cxxOperatorCallExpr(Matcher), this);
+}
+
+void KnownLiveChecker::check(const MatchFinder::MatchResult &Result) {
+  const char *Error = "MOZ_KNOWN_LIVE members can only be modified by "
+                      "constructors and destructors";
+
+  if (const MemberExpr *Expr = Result.Nodes.getNodeAs<MemberExpr>("lhs")) {
+    diag(Expr->getBeginLoc(), Error, DiagnosticIDs::Error);
+  }
+  if (const CXXOperatorCallExpr *Expr =
+          Result.Nodes.getNodeAs<CXXOperatorCallExpr>("lhs")) {
+    diag(Expr->getBeginLoc(), Error, DiagnosticIDs::Error);
+  }
+}