1 files changed, 91 insertions, 0 deletions
diff --git a/build/clang-plugin/TemporaryLifetimeBoundChecker.cpp b/build/clang-plugin/TemporaryLifetimeBoundChecker.cpp
new file mode 100644
index 0000000000..dc66f62b0d
--- /dev/null
+++ b/build/clang-plugin/TemporaryLifetimeBoundChecker.cpp
@@ -0,0 +1,91 @@
+/* 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 "TemporaryLifetimeBoundChecker.h"
+#include "CustomMatchers.h"
+#include "clang/Lex/Lexer.h"
+
+void TemporaryLifetimeBoundChecker::registerMatchers(MatchFinder *AstMatcher) {
+  // Look for a call to a MOZ_LIFETIME_BOUND member function
+  auto isTemporaryLifetimeBoundCall =
+      cxxMemberCallExpr(
+          onImplicitObjectArgument(anyOf(has(cxxTemporaryObjectExpr()),
+                                         has(materializeTemporaryExpr()))),
+          callee(functionDecl(isMozTemporaryLifetimeBound())))
+          .bind("call");
+
+  // XXX This definitely does not catch everything relevant. In particular, the
+  // matching on conditionalOperator would need to be recursive. But it's a
+  // start.
+  auto hasTemporaryLifetimeBoundCall =
+      anyOf(isTemporaryLifetimeBoundCall,
+            conditionalOperator(
+                anyOf(hasFalseExpression(isTemporaryLifetimeBoundCall),
+                      hasTrueExpression(isTemporaryLifetimeBoundCall))));
+
+  AstMatcher->addMatcher(
+      returnStmt(hasReturnValue(
+                     allOf(exprWithCleanups().bind("expr-with-cleanups"),
+                           ignoringParenCasts(hasTemporaryLifetimeBoundCall))))
+          .bind("return-stmt"),
+      this);
+
+  AstMatcher->addMatcher(
+      varDecl(hasType(references(cxxRecordDecl())),
+              hasInitializer(
+                  allOf(exprWithCleanups(),
+                        ignoringParenCasts(hasTemporaryLifetimeBoundCall))))
+          .bind("var-decl"),
+      this);
+}
+
+void TemporaryLifetimeBoundChecker::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Call = Result.Nodes.getNodeAs<CXXMemberCallExpr>("call");
+  const auto *ReturnStatement =
+      Result.Nodes.getNodeAs<ReturnStmt>("return-stmt");
+  const auto *ReferenceVarDecl = Result.Nodes.getNodeAs<VarDecl>("var-decl");
+
+  const char ErrorReturn[] =
+      "cannot return result of lifetime-bound function %0 on "
+      "temporary of type %1";
+
+  const char ErrorBindToReference[] =
+      "cannot bind result of lifetime-bound function %0 on "
+      "temporary of type %1 to reference, does not extend lifetime";
+
+  const char NoteCalledFunction[] = "member function declared here";
+
+  // We are either a return statement...
+  if (ReturnStatement) {
+    const auto *ExprWithCleanups =
+        Result.Nodes.getNodeAs<Expr>("expr-with-cleanups");
+    if (!ExprWithCleanups->isLValue()) {
+      return;
+    }
+
+    const auto Range = ReturnStatement->getSourceRange();
+
+    diag(Range.getBegin(), ErrorReturn, DiagnosticIDs::Error)
+        << Range << Call->getMethodDecl()
+        << Call->getImplicitObjectArgument()
+               ->getType()
+               .withoutLocalFastQualifiers();
+  }
+
+  // ... or a variable declaration that declare a reference
+  if (ReferenceVarDecl) {
+    const auto Range = ReferenceVarDecl->getSourceRange();
+
+    diag(Range.getBegin(), ErrorBindToReference, DiagnosticIDs::Error)
+        << Range << Call->getMethodDecl()
+        << Call->getImplicitObjectArgument()
+               ->getType()
+               .withoutLocalFastQualifiers();
+  }
+
+  const auto *MethodDecl = Call->getMethodDecl();
+  diag(MethodDecl->getCanonicalDecl()->getLocation(), NoteCalledFunction,
+       DiagnosticIDs::Note);
+}