Bug 1268754 - Tweak some MFBT return values. r=Ms2ger.

This patch:

- Adds MOZ_MUST_USE to AllocPolicy::checkSimulatedOOM().

- Adds MOZ_MUST_USE to LZ4::decompress() (both variants) and fixes their
  comments.

- Changes the return type of SplayTree::insert() from bool to void, because it
  always returns true and its callers don't check the return value.

- Changes the return type of SplayTree::finishInsertion() from T* to void,
  because it makes things clearer -- it was just returning the aNew argument.

- Adds MOZ_MUST_USE to a Vector::growTo() (both variants).

--HG--
extra : rebase_source : 1547cdeb9ee71d0ecec608ab474ab5e75bfc4b42

mfbt/AllocPolicy.h

@@ -121,7 +121,7 @@ class MallocAllocPolicy
   {
   }
 
-  bool checkSimulatedOOM() const
+  MOZ_MUST_USE bool checkSimulatedOOM() const
   {
     return true;
   }

mfbt/Compression.h

@@ -61,8 +61,7 @@ class LZ4
 
   /**
    * If the source stream is malformed, the function will stop decoding
-   * and return a negative result, indicating the byte position of the
-   * faulty instruction
+   * and return false.
    *
    * This function never writes outside of provided buffers, and never
    * modifies input buffer.
@@ -71,9 +70,9 @@ class LZ4
    *       minimum of |aOutputSize| bytes.
    *
    * @param aOutputSize is the output size, therefore the original size
-   * @return the number of bytes read in the source buffer
+   * @return true on success, false on failure
    */
-  static MFBT_API bool
+  static MFBT_API MOZ_MUST_USE bool
   decompress(const char* aSource, char* aDest, size_t aOutputSize);
 
   /**
@@ -91,8 +90,9 @@ class LZ4
    *   already allocated)
    * @param aOutputSize the actual number of bytes decoded in the destination
    *   buffer (necessarily <= aMaxOutputSize)
+   * @return true on success, false on failure
    */
-  static MFBT_API bool
+  static MFBT_API MOZ_MUST_USE bool
   decompress(const char* aSource, size_t aInputSize, char* aDest,
              size_t aMaxOutputSize, size_t* aOutputSize);
 

mfbt/SplayTree.h

@@ -76,19 +76,19 @@ class SplayTree
     return Comparator::compare(aValue, *last) == 0 ? last : nullptr;
   }
 
-  bool insert(T* aValue)
+  void insert(T* aValue)
   {
     MOZ_ASSERT(!find(*aValue), "Duplicate elements are not allowed.");
 
     if (!mRoot) {
       mRoot = aValue;
-      return true;
+      return;
     }
     T* last = lookup(*aValue);
     int cmp = Comparator::compare(*aValue, *last);
 
     finishInsertion(last, cmp, aValue);
-    return true;
+    return;
   }
 
   T* findOrInsert(const T& aValue);
@@ -194,7 +194,7 @@ class SplayTree
     return parent;
   }
 
-  T* finishInsertion(T* aLast, int32_t aCmp, T* aNew)
+  void finishInsertion(T* aLast, int32_t aCmp, T* aNew)
   {
     MOZ_ASSERT(aCmp, "Nodes shouldn't be equal!");
 
@@ -204,7 +204,6 @@ class SplayTree
     aNew->mParent = aLast;
 
     splay(aNew);
-    return aNew;
   }
 
   /**
@@ -321,7 +320,9 @@ SplayTree<T, Comparator>::findOrInsert(const T& aValue)
     return last;
   }
 
-  return finishInsertion(last, cmp, new T(aValue));
+  T* t = new T(aValue);
+  finishInsertion(last, cmp, t);
+  return t;
 }
 
 }  /* namespace mozilla */

mfbt/Vector.h

@@ -128,7 +128,7 @@ struct VectorImpl
    * aNewCap has not overflowed, and (2) multiplying aNewCap by sizeof(T) will
    * not overflow.
    */
-  static inline bool
+  static inline MOZ_MUST_USE bool
   growTo(Vector<T, N, AP>& aV, size_t aNewCap)
   {
     MOZ_ASSERT(!aV.usingInlineStorage());
@@ -215,7 +215,7 @@ struct VectorImpl<T, N, AP, true>
     }
   }
 
-  static inline bool
+  static inline MOZ_MUST_USE bool
   growTo(Vector<T, N, AP>& aV, size_t aNewCap)
   {
     MOZ_ASSERT(!aV.usingInlineStorage());