Changeset 52500 in webkit for trunk/JavaScriptCore/runtime

Timestamp:

Dec 22, 2009, 2:05:17 PM (15 years ago)

Author:

[email protected]

Message:

Fix a couple of problems with UntypedPtrAndBitfield.

Reviewed by Sam Weinig.

Add a m_leaksPtr to reduce false positives from leaks in debug builds
(this isn't perfect because we'd like a solution for release builds,
but this is now at least as good as a PtrAndFlags would be).

Switch SmallStringsto use a regular string for the base, rather than
a static one. UntypedPtrAndBitfield assumes all strings are at least
8 byte aligned; this migt not be true of static strings. Shared buffers
are heap allocated, as are all UStringImpls other than static strings.
Static strings cannot end up being the owner string of substrings,
since the only static strings are length 0.

• runtime/SmallStrings.cpp:

(JSC::SmallStringsStorage::SmallStringsStorage):

• runtime/UStringImpl.h:

(JSC::UntypedPtrAndBitfield::UntypedPtrAndBitfield):
(JSC::UStringImpl::UStringImpl):

Location:

trunk/JavaScriptCore/runtime

Files:

• SmallStrings.cpp (modified) (1 diff)
• UStringImpl.h (modified) (3 diffs)

trunk/JavaScriptCore/runtime/SmallStrings.cpp

@@ -42 +42 @@
 
 private:
-    UChar m_characters[numCharactersToStore];
-    UString::Rep m_base;
     UString::Rep m_reps[numCharactersToStore];
 };
 
 SmallStringsStorage::SmallStringsStorage()
-    : m_base(m_characters, numCharactersToStore, UStringImpl::ConstructStaticString)
 {
-    m_base.checkConsistency();
-
-    for (unsigned i = 0; i < numCharactersToStore; ++i)
-        m_characters[i] = i;
-
-    memset(&m_reps, 0, sizeof(m_reps));
-    for (unsigned i = 0; i < numCharactersToStore; ++i)
-        new (&m_reps[i]) UString::Rep(m_base.data() + i, 1, &m_base);
+    UChar* characterBuffer = 0;
+    RefPtr<UStringImpl> baseString = UStringImpl::createUninitialized(numCharactersToStore, characterBuffer);
+    for (unsigned i = 0; i < numCharactersToStore; ++i) {
+        characterBuffer[i] = i;
+        new (&m_reps[i]) UString::Rep(&characterBuffer[i], 1, PassRefPtr<UStringImpl>(baseString));
+    }
 }
 

trunk/JavaScriptCore/runtime/UStringImpl.h

@@ -45 +45 @@
     UntypedPtrAndBitfield(void* ptrValue, uintptr_t bitValue)
         : m_value(reinterpret_cast<uintptr_t>(ptrValue) | bitValue)
+#ifndef NDEBUG
+        , m_leaksPtr(ptrValue)
+#endif
     {
         ASSERT(ptrValue == asPtr<void*>());
@@ -73 +76 @@
     static const uintptr_t s_alignmentMask = ~static_cast<uintptr_t>(0x7);
     uintptr_t m_value;
+#ifndef NDEBUG
+        void* m_leaksPtr; // Only used to allow tools like leaks on OSX to detect that the memory is referenced.
+#endif
 };
 
@@ -217 +223 @@
         , m_dataBuffer(base.releaseRef(), BufferSubstring)
     {
+        // Do use static strings as a base for substrings; UntypedPtrAndBitfield assumes
+        // that all pointers will be at least 8-byte aligned, we cannot guarantee that of
+        // UStringImpls that are not heap allocated.
+        ASSERT(m_dataBuffer.asPtr<UStringImpl*>()->size());
+        ASSERT(!m_dataBuffer.asPtr<UStringImpl*>()->isStatic());
         checkConsistency();
     }