Changeset 138308 in webkit for trunk/Source/JavaScriptCore/jit/JITWriteBarrier.h

Timestamp:

Dec 20, 2012, 3:20:30 PM (12 years ago)

Author:

[email protected]

Message:

JIT: Change uninitialized pointer value -1 to constant
​https://bugs.webkit.org/show_bug.cgi?id=105576

Rubber stamped by Gavin Barraclough.

Changed the use of -1 as a pointer value in the JITs to be the constant unusedPointer defined in the
new file jit/UnusedPointer.h. Made it's value 0xd1e7beef, which is a bad pointer on most architectures
because it is odd, and to distinguish it from other common values.

• GNUmakefile.list.am:
• JavaScriptCore.xcodeproj/project.pbxproj:
• dfg/DFGRepatch.cpp:

(JSC::DFG::dfgResetGetByID):
(JSC::DFG::dfgResetPutByID):

• dfg/DFGSpeculativeJIT32_64.cpp:

(JSC::DFG::SpeculativeJIT::cachedGetById):
(JSC::DFG::SpeculativeJIT::cachedPutById):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::cachedGetById):
(JSC::DFG::SpeculativeJIT::cachedPutById):

• jit/JIT.h:
• jit/JITPropertyAccess.cpp:

(JSC::JIT::resetPatchGetById):
(JSC::JIT::resetPatchPutById):

• jit/JITPropertyAccess32_64.cpp:

(JSC::JIT::resetPatchGetById):
(JSC::JIT::resetPatchPutById):

• jit/JITWriteBarrier.h:

(JSC::JITWriteBarrierBase::clearToUnusedPointer):
(JSC::JITWriteBarrierBase::get):

• jit/UnusedPointer.h: Added.

File:

• trunk/Source/JavaScriptCore/jit/JITWriteBarrier.h (modified) (3 diffs)

trunk/Source/JavaScriptCore/jit/JITWriteBarrier.h

@@ -32 +32 @@
 #include "SlotVisitor.h"
 #include "WriteBarrier.h"
+#include "jit/UnusedPointer.h"
 
 namespace JSC {
@@ -70 +71 @@
     
     void clear() { clear(0); }
-    void clearToMaxUnsigned() { clear(reinterpret_cast<void*>(-1)); }
+    void clearToUnusedPointer() { clear(reinterpret_cast<void*>(unusedPointer)); }
 
 protected:
@@ -91 +92 @@
             return 0;
         void* result = static_cast<JSCell*>(MacroAssembler::readPointer(m_location));
-        // We use -1 to indicate a "safe" empty value in the instruction stream
-        if (result == (void*)-1)
+        if (result == reinterpret_cast<void*>(unusedPointer))
             return 0;
         return static_cast<JSCell*>(result);