1 files changed, 114 insertions, 0 deletions
diff --git a/build/clang-plugin/KungFuDeathGripChecker.cpp b/build/clang-plugin/KungFuDeathGripChecker.cpp
new file mode 100644
index 0000000000..03bb20514f
--- /dev/null
+++ b/build/clang-plugin/KungFuDeathGripChecker.cpp
@@ -0,0 +1,114 @@
+/* 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 "KungFuDeathGripChecker.h"
+#include "CustomMatchers.h"
+
+void KungFuDeathGripChecker::registerMatchers(MatchFinder *AstMatcher) {
+  AstMatcher->addMatcher(varDecl(allOf(hasType(isRefPtr()), hasLocalStorage(),
+                                       hasInitializer(anything())))
+                             .bind("decl"),
+                         this);
+}
+
+void KungFuDeathGripChecker::check(const MatchFinder::MatchResult &Result) {
+  const char *Error = "Unused \"kungFuDeathGrip\" %0 objects constructed from "
+                      "%1 are prohibited";
+  const char *Note = "Please switch all accesses to this %0 to go through "
+                     "'%1', or explicitly pass '%1' to `mozilla::Unused`";
+
+  const VarDecl *D = Result.Nodes.getNodeAs<VarDecl>("decl");
+  if (D->isReferenced()) {
+    return;
+  }
+
+  // Not interested in parameters.
+  if (isa<ImplicitParamDecl>(D) || isa<ParmVarDecl>(D)) {
+    return;
+  }
+
+  const Expr *E = IgnoreTrivials(D->getInit());
+  const CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(E);
+  if (CE && CE->getNumArgs() == 0) {
+    // We don't report an error when we construct and don't use a nsCOMPtr /
+    // nsRefPtr with no arguments. We don't report it because the error is not
+    // related to the current check. In the future it may be reported through a
+    // more generic mechanism.
+    return;
+  }
+
+  // We don't want to look at the single argument conversion constructors
+  // which are inbetween the declaration and the actual object which we are
+  // assigning into the nsCOMPtr/RefPtr. To do this, we repeatedly
+  // IgnoreTrivials, then look at the expression. If it is one of these
+  // conversion constructors, we ignore it and continue to dig.
+  while ((CE = dyn_cast<CXXConstructExpr>(E)) && CE->getNumArgs() == 1) {
+    E = IgnoreTrivials(CE->getArg(0));
+  }
+
+  // If the argument expression is an xvalue, we are not taking a copy of
+  // anything.
+  if (E->isXValue()) {
+    return;
+  }
+
+  // It is possible that the QualType doesn't point to a type yet so we are
+  // not interested.
+  if (E->getType().isNull()) {
+    return;
+  }
+
+  // We allow taking a kungFuDeathGrip of `this` because it cannot change
+  // beneath us, so calling directly through `this` is OK. This is the same
+  // for local variable declarations.
+  //
+  // We also don't complain about unused RefPtrs which are constructed from
+  // the return value of a new expression, as these are required in order to
+  // immediately destroy the value created (which was presumably created for
+  // its side effects), and are not used as a death grip.
+  if (isa<CXXThisExpr>(E) || isa<DeclRefExpr>(E) || isa<CXXNewExpr>(E)) {
+    return;
+  }
+
+  // These types are assigned into nsCOMPtr and RefPtr for their side effects,
+  // and not as a kungFuDeathGrip. We don't want to consider RefPtr and nsCOMPtr
+  // types which are initialized with these types as errors.
+  const TagDecl *TD = E->getType()->getAsTagDecl();
+  if (TD && TD->getIdentifier()) {
+    static const char *IgnoreTypes[] = {
+        "already_AddRefed",
+        "nsGetServiceByCID",
+        "nsGetServiceByCIDWithError",
+        "nsGetServiceByContractID",
+        "nsGetServiceByContractIDWithError",
+        "nsCreateInstanceByCID",
+        "nsCreateInstanceByContractID",
+        "nsCreateInstanceFromFactory",
+    };
+
+    for (uint32_t i = 0; i < sizeof(IgnoreTypes) / sizeof(IgnoreTypes[0]);
+         ++i) {
+      if (TD->getName() == IgnoreTypes[i]) {
+        return;
+      }
+    }
+  }
+
+  // Report the error
+  const char *ErrThing;
+  const char *NoteThing;
+  if (isa<MemberExpr>(E)) {
+    ErrThing = "members";
+    NoteThing = "member";
+  } else {
+    ErrThing = "temporary values";
+    NoteThing = "value";
+  }
+
+  // We cannot provide the note if we don't have an initializer
+  diag(D->getBeginLoc(), Error, DiagnosticIDs::Error)
+      << D->getType() << ErrThing;
+  diag(E->getBeginLoc(), Note, DiagnosticIDs::Note)
+      << NoteThing << getNameChecked(D);
+}