Changeset 56092 in webkit

Timestamp:

Mar 16, 2010 4:14:31 PM (14 years ago)

Author:

barraclough@apple.com

Message:

Bug 36083 - REGRESSION (r55772-r55834): Crash in JavaScriptCore RegExp code on PowerPC

Reviewed by Oliver Hunt, Darin Adler.

The problem is a bug in our port of PCRE - that a read may take place from the first character in an
empty string. For the time being, revert to using a valid pointer in the data segment rather than
an invalid non-null pointer into the zero-page for the empty string's data pointer. A better fix for
this will be to remove PCRE.

• runtime/UStringImpl.cpp:

(JSC::UStringImpl::empty):

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/UStringImpl.cpp (modified) (1 diff)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2010-03-16  Gavin Barraclough  <barraclough@apple.com>
+
+        Reviewed by Oliver Hunt, Darin Adler.
+
+        Bug 36083 - REGRESSION (r55772-r55834): Crash in JavaScriptCore RegExp code on PowerPC
+
+        The problem is a bug in our port of PCRE - that a read may take place from the first character in an
+        empty string.  For the time being, revert to using a valid pointer in the data segment rather than
+        an invalid non-null pointer into the zero-page for the empty string's data pointer.  A better fix for
+        this will be to remove PCRE.
+
+        * runtime/UStringImpl.cpp:
+        (JSC::UStringImpl::empty):
+
 2010-03-16  Darin Adler  <darin@apple.com>
 

trunk/JavaScriptCore/runtime/UStringImpl.cpp

@@ -65 +65 @@
 UStringImpl* UStringImpl::empty()
 {
-    // A non-null pointer at an invalid address (in page zero) so that if it were to be accessed we
-    // should catch the error with fault (however it should be impossible to access, since length is zero).
-    static const UChar* invalidNonNullUCharPtr = reinterpret_cast<UChar*>(static_cast<intptr_t>(1));
-    DEFINE_STATIC_LOCAL(UStringImpl, emptyString, (invalidNonNullUCharPtr, 0, ConstructStaticString));
+    // FIXME: This works around a bug in our port of PCRE, that a regular expression
+    // run on the empty string may still perform a read from the first element, and
+    // as such we need this to be a valid pointer. No code should ever be reading
+    // from a zero length string, so this should be able to be a non-null pointer
+    // into the zero-page.
+    // Replace this with 'reinterpret_cast<UChar*>(static_cast<intptr_t>(1))' once
+    // PCRE goes away.
+    static UChar emptyUCharData = 0;
+    DEFINE_STATIC_LOCAL(UStringImpl, emptyString, (&emptyUCharData, 0, ConstructStaticString));
     return &emptyString;
 }