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obstack.h __PTR_ALIGN vs. ubsan

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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.

	* obstack.h (__PTR_ALIGN): Expand and simplify __BPTR_ALIGN
	rather than calculating relative to a NULL pointer.
This commit is contained in:
Alan Modra 2021-09-02 09:05:05 +09:30
parent a9b3c451be
commit b032103265
1 changed files with 3 additions and 3 deletions
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4
include/obstack.h
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@ -138,8 +138,8 @@
alignment relative to 0. */
#define __PTR_ALIGN(B, P, A) \
__BPTR_ALIGN (sizeof (ptrdiff_t) < sizeof (void *) ? (B) : (char *) 0, \
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