Bug 1331434 - Part 2: Add MOZ_MAY_CALL_AFTER_MUST_RETURN and MOZ_MUST…

…_RETURN_FROM_CALLER annotations, r=ehsan MozReview-Commit-ID: 1o2egvdhkqT
dothq · Mar 8, 2017 · 46ade67 · 46ade67
1 parent 4689eec
commit 46ade67
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Showing 4 changed files with 42 additions and 4 deletions.
diff --git a/dom/bindings/ErrorResult.h b/dom/bindings/ErrorResult.h
@@ -165,11 +165,48 @@ class TErrorResult {
   operator ErrorResult&();
   operator OOMReporter&();
 
-  void Throw(nsresult rv) {
+  void MOZ_MUST_RETURN_FROM_CALLER Throw(nsresult rv) {
     MOZ_ASSERT(NS_FAILED(rv), "Please don't try throwing success");
     AssignErrorCode(rv);
   }
 
+  // This method acts identically to the `Throw` method, however, it does not
+  // have the MOZ_MUST_RETURN_FROM_CALLER static analysis annotation. It is
+  // intended to be used in situations when additional work needs to be
+  // performed in the calling function after the Throw method is called.
+  //
+  // In general you should prefer using `Throw`, and returning after an error,
+  // for example:
+  //
+  //   if (condition) {
+  //     aRv.Throw(NS_ERROR_FAILURE);
+  //     return;
+  //   }
+  //
+  // or
+  //
+  //   if (condition) {
+  //     aRv.Throw(NS_ERROR_FAILURE);
+  //   }
+  //   return;
+  //
+  // However, if you need to do some other work after throwing, such as:
+  //
+  //   if (condition) {
+  //     aRv.ThrowWithCustomCleanup(NS_ERROR_FAILURE);
+  //   }
+  //   // Do some important clean-up work which couldn't happen earlier.
+  //   // We want to do this clean-up work in both the success and failure cases.
+  //   CleanUpImportantState();
+  //   return;
+  //
+  // Then you'll need to use ThrowWithCustomCleanup to get around the static
+  // analysis, which would complain that you are doing work after the call to
+  // `Throw()`.
+  void ThrowWithCustomCleanup(nsresult rv) {
+    Throw(rv);
+  }
+
   // Duplicate our current state on the given TErrorResult object.  Any
   // existing errors or messages on the target will be suppressed before
   // cloning.  Our own error state remains unchanged.
@@ -307,7 +344,7 @@ class TErrorResult {
   }
 
   // Support for uncatchable exceptions.
-  void ThrowUncatchableException() {
+  void MOZ_MUST_RETURN_FROM_CALLER ThrowUncatchableException() {
     Throw(NS_ERROR_UNCATCHABLE_EXCEPTION);
   }
   bool IsUncatchableException() const {

diff --git a/js/public/Value.h b/js/public/Value.h
@@ -966,7 +966,7 @@ ExposeValueToActiveJS(const Value& v)
 
 /************************************************************************/
 
-static inline Value
+static inline MOZ_MAY_CALL_AFTER_MUST_RETURN Value
 NullValue()
 {
     Value v;

diff --git a/mfbt/RefPtr.h b/mfbt/RefPtr.h
@@ -251,6 +251,7 @@ class RefPtr
   }
 
   already_AddRefed<T>
+  MOZ_MAY_CALL_AFTER_MUST_RETURN
   forget()
   // return the value of mRawPtr and null out mRawPtr. Useful for
   // already_AddRefed return values.

diff --git a/xpcom/base/nsCOMPtr.h b/xpcom/base/nsCOMPtr.h
@@ -717,7 +717,7 @@ class nsCOMPtr final
 
   // Return the value of mRawPtr and null out mRawPtr. Useful for
   // already_AddRefed return values.
-  already_AddRefed<T> forget()
+  already_AddRefed<T> MOZ_MAY_CALL_AFTER_MUST_RETURN forget()
   {
     T* temp = nullptr;
     swap(temp);