Title: [281317] trunk/Source/WTF
- Revision
- 281317
- Author
- [email protected]
- Date
- 2021-08-20 08:53:13 -0700 (Fri, 20 Aug 2021)
Log Message
Remove assertIsTagged and assertIsNullOrTagged.
https://bugs.webkit.org/show_bug.cgi?id=229329
rdar://82162851
Reviewed by Yusuke Suzuki.
These assertion utility functions rely on tagged pointers always having non-zero
PAC bits. This is an incorrect assumption. A tagged pointer can have PAC bits
that are completely zero. Hence, these assert functions cannot be made to work
reliably. We should remove them to prevent them from being used, and potentially
resulting in flaky assertion failures that will be hard to debug later.
Note: assertIsNotTagged is fine to keep. It asserts that PAC bits of a pointer
are all 0. As a result, this assertion can have false positives where it may think
a tagged pointer is an untagged pointer. However, this is rare because it is not
common to have 0 PAC bits in tagged pointers. False positives on this assertion
won't result in flaky test failures that will waste our time later. Hence,
keeping the assertion will do more good (it will tend to help us find bugs) than
bad (it will rarely let false positives thru). As a result, I'm opting to not
remove it.
* wtf/PtrTag.h:
(WTF::assertIsTagged): Deleted.
(WTF::assertIsNullOrTagged): Deleted.
Modified Paths
Diff
Modified: trunk/Source/WTF/ChangeLog (281316 => 281317)
--- trunk/Source/WTF/ChangeLog 2021-08-20 15:30:03 UTC (rev 281316)
+++ trunk/Source/WTF/ChangeLog 2021-08-20 15:53:13 UTC (rev 281317)
@@ -1,3 +1,30 @@
+2021-08-20 Mark Lam <[email protected]>
+
+ Remove assertIsTagged and assertIsNullOrTagged.
+ https://bugs.webkit.org/show_bug.cgi?id=229329
+ rdar://82162851
+
+ Reviewed by Yusuke Suzuki.
+
+ These assertion utility functions rely on tagged pointers always having non-zero
+ PAC bits. This is an incorrect assumption. A tagged pointer can have PAC bits
+ that are completely zero. Hence, these assert functions cannot be made to work
+ reliably. We should remove them to prevent them from being used, and potentially
+ resulting in flaky assertion failures that will be hard to debug later.
+
+ Note: assertIsNotTagged is fine to keep. It asserts that PAC bits of a pointer
+ are all 0. As a result, this assertion can have false positives where it may think
+ a tagged pointer is an untagged pointer. However, this is rare because it is not
+ common to have 0 PAC bits in tagged pointers. False positives on this assertion
+ won't result in flaky test failures that will waste our time later. Hence,
+ keeping the assertion will do more good (it will tend to help us find bugs) than
+ bad (it will rarely let false positives thru). As a result, I'm opting to not
+ remove it.
+
+ * wtf/PtrTag.h:
+ (WTF::assertIsTagged): Deleted.
+ (WTF::assertIsNullOrTagged): Deleted.
+
2021-08-19 Antti Koivisto <[email protected]>
[:has() pseudo-class] Basic support
Modified: trunk/Source/WTF/wtf/PtrTag.h (281316 => 281317)
--- trunk/Source/WTF/wtf/PtrTag.h 2021-08-20 15:30:03 UTC (rev 281316)
+++ trunk/Source/WTF/wtf/PtrTag.h 2021-08-20 15:53:13 UTC (rev 281317)
@@ -318,20 +318,6 @@
WTF_PTRTAG_ASSERT(PtrTagAction::DebugAssert, ptr, NoPtrTag, ptr == removeCodePtrTag(ptr));
}
-template<typename PtrType>
-void assertIsTagged(PtrType value)
-{
- void* ptr = bitwise_cast<void*>(value);
- WTF_PTRTAG_ASSERT(PtrTagAction::DebugAssert, ptr, AnyPtrTag, ptr != removeCodePtrTag(ptr));
-}
-
-template<typename PtrType>
-void assertIsNullOrTagged(PtrType ptr)
-{
- if (ptr)
- assertIsTagged(ptr);
-}
-
template<PtrTag tag, typename PtrType>
bool isTaggedWith(PtrType value)
{
@@ -578,8 +564,6 @@
using WTF::assertIsCFunctionPtr;
using WTF::assertIsNullOrCFunctionPtr;
using WTF::assertIsNotTagged;
-using WTF::assertIsTagged;
-using WTF::assertIsNullOrTagged;
using WTF::isTaggedWith;
using WTF::assertIsTaggedWith;
using WTF::assertIsNullOrTaggedWith;
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