Current ubsan complains on every use of __PTR_ALIGN (when ptrdiff_t is
as large as a pointer), due to making calculations relative to a NULL
pointer. This patch avoids the problem by extracting out and
simplifying __BPTR_ALIGN for the usual case. I've continued to use
ptrdiff_t here, where it might be better to throw away __BPTR_ALIGN
entirely and just assume uintptr_t exists.
OK to apply for gcc?
* obstack.h (__PTR_ALIGN): Expand and simplify __BPTR_ALIGN
rather than calculating relative to a NULL pointer.
diff --git a/include/obstack.h b/include/obstack.h
index a6eb6c95587..0d8746f835b 100644
--- a/include/obstack.h
+++ b/include/obstack.h
@@ -137,9 +137,9 @@
relative to B. Otherwise, use the faster strategy of computing the
alignment relative to 0. */
-#define __PTR_ALIGN(B, P, A) \
- __BPTR_ALIGN (sizeof (ptrdiff_t) < sizeof (void *) ? (B) : (char *) 0, \
-P, A)
+#define __PTR_ALIGN(B, P, A) \
+ (sizeof (ptrdiff_t) < sizeof (void *) ? __BPTR_ALIGN (B, P, A) \
+ : (char *) (((ptrdiff_t) (P) + (A)) & ~(A)))
#ifndef __attribute_pure__
# if defined __GNUC_MINOR__ && __GNUC__ * 1000 + __GNUC_MINOR__ >= 2096
--
Alan Modra
Australia Development Lab, IBM
