Reviewers: jochen (slow),
Message:
Hey, I've been looking at ubsan warnings in chrome, and taking a stab at
fixing
some of the low hanging fruit. This shouldn't make any difference in the
generated code, but might as well clean up some of the noise in the ubsan
output.
Description:
Use 16 instead of 4 for determining member offsets.
This avoids UBSan warnings about unaligned memory access.
BUG=
Please review this at https://codereview.chromium.org/734873002/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+4, -4 lines):
M src/base/macros.h
M src/heap/heap-inl.h
Index: src/base/macros.h
diff --git a/src/base/macros.h b/src/base/macros.h
index
80a89496a5e25bc06caf3aa6445cdbb11b484303..371d7da6eaa72251a9693096f64a79def1b8fa49
100644
--- a/src/base/macros.h
+++ b/src/base/macros.h
@@ -20,9 +20,9 @@
// corresponds to 'offsetof' (in stddef.h), except that it doesn't
// use 0 or NULL, which causes a problem with the compiler warnings
// we have enabled (which is also why 'offsetof' doesn't seem to work).
-// Here we simply use the non-zero value 4, which seems to work.
-#define OFFSET_OF(type, field) \
- (reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(4)->field)) - 4)
+// Here we simply use the aligned, non-zero value 16.
+#define OFFSET_OF(type, field) \
+ (reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(16)->field)) - 16)
#if V8_OS_NACL
Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index
48e928d71106c1f7785b04d4cc7eebb8bd1b3de8..549ecbc9a64eafe8f93c77c67e7e90d1f6a9afe2
100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -587,7 +587,7 @@ bool Heap::CollectGarbage(AllocationSpace space, const
char* gc_reason,
Isolate* Heap::isolate() {
return reinterpret_cast<Isolate*>(
reinterpret_cast<intptr_t>(this) -
- reinterpret_cast<size_t>(reinterpret_cast<Isolate*>(4)->heap()) + 4);
+ reinterpret_cast<size_t>(reinterpret_cast<Isolate*>(16)->heap()) +
16);
}
--
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