Bug 858671. Make do_GetAtom infallible. r=khuey

xpcom/ds/nsAtomTable.cpp

@@ -478,43 +478,52 @@ NS_SizeOfAtomTablesIncludingThis(nsMallocSizeOfFun aMallocSizeOf) {
 
 #define ATOM_HASHTABLE_INITIAL_SIZE  4096
 
-static inline bool
+static void HandleOOM()
+{
+  fputs("Out of memory allocating atom hashtable.\n", stderr);
+  MOZ_CRASH();
+  MOZ_NOT_REACHED();
+}
+
+static inline void
 EnsureTableExists()
 {
-  if (gAtomTable.ops) {
-    return true;
+  if (!gAtomTable.ops &&
+      !PL_DHashTableInit(&gAtomTable, &AtomTableOps, 0,
+                         sizeof(AtomTableEntry), ATOM_HASHTABLE_INITIAL_SIZE)) {
+    // Initialization failed.
+    HandleOOM();
   }
-  if (PL_DHashTableInit(&gAtomTable, &AtomTableOps, 0,
-                        sizeof(AtomTableEntry), ATOM_HASHTABLE_INITIAL_SIZE)) {
-    return true;
-  }
-  // Initialization failed.
-  gAtomTable.ops = nullptr;
-  return false;
 }
 
 static inline AtomTableEntry*
 GetAtomHashEntry(const char* aString, uint32_t aLength)
 {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
-  if (!EnsureTableExists()) {
-    return nullptr;
-  }
+  EnsureTableExists();
   AtomTableKey key(aString, aLength);
-  return static_cast<AtomTableEntry*>
-                    (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
+  AtomTableEntry* e =
+    static_cast<AtomTableEntry*>
+               (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
+  if (!e) {
+    HandleOOM();
+  }
+  return e;
 }
 
 static inline AtomTableEntry*
 GetAtomHashEntry(const PRUnichar* aString, uint32_t aLength)
 {
   MOZ_ASSERT(NS_IsMainThread(), "wrong thread");
-  if (!EnsureTableExists()) {
-    return nullptr;
-  }
+  EnsureTableExists();
   AtomTableKey key(aString, aLength);
-  return static_cast<AtomTableEntry*>
-                    (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
+  AtomTableEntry* e =
+    static_cast<AtomTableEntry*>
+               (PL_DHashTableOperate(&gAtomTable, &key, PL_DHASH_ADD));
+  if (!e) {
+    HandleOOM();
+  }
+  return e;
 }
 
 class CheckStaticAtomSizes

xpcom/ds/nsIAtom.idl

@@ -97,7 +97,7 @@ protected:
 
 /**
  * Find an atom that matches the given UTF-8 string.
- * The string is assumed to be zero terminated.
+ * The string is assumed to be zero terminated.  Never returns null.
  */
 extern nsIAtom* NS_NewAtom(const char* aUTF8String);
 
@@ -105,7 +105,7 @@ inline already_AddRefed<nsIAtom> do_GetAtom(const char* aUTF8String)
     { return NS_NewAtom(aUTF8String); }
  
 /**
- * Find an atom that matches the given UTF-8 string.
+ * Find an atom that matches the given UTF-8 string.  Never returns null.
  */
 extern nsIAtom* NS_NewAtom(const nsACString& aUTF8String);
 inline already_AddRefed<nsIAtom> do_GetAtom(const nsACString& aUTF8String)
@@ -113,14 +113,14 @@ inline already_AddRefed<nsIAtom> do_GetAtom(const nsACString& aUTF8String)
 
 /**
  * Find an atom that matches the given UTF-16 string.
- * The string is assumed to be zero terminated.
+ * The string is assumed to be zero terminated.  Never returns null.
  */
 extern nsIAtom* NS_NewAtom(const PRUnichar* aUTF16String);
 inline already_AddRefed<nsIAtom> do_GetAtom(const PRUnichar* aUTF16String)
     { return NS_NewAtom(aUTF16String); }
 
 /**
- * Find an atom that matches the given UTF-16 string.
+ * Find an atom that matches the given UTF-16 string.  Never returns null.
  */
 extern nsIAtom* NS_NewAtom(const nsAString& aUTF16String);
 extern nsIAtom* NS_NewPermanentAtom(const nsAString& aUTF16String);