The code depends on the presence of uintptr_t,
not on whether ptrdiff_t is narrower than a pointer,
so use C macros that reflect this.
Also, clean up the namespace in the typical GCC-like case
* lib/obstack.in.h (_OBSTACK_UINTPTR_TYPE): New macro.
Include <stdint.h> only if needed (i.e., not GCC-like).
(__PTR_ALIGN): Use new macro instead of relying on
__GL_SMALL_PTRDIFF_T__ and directly on uintptr_t.
* m4/obstack.m4 (gl_FUNC_OBSTACK): Simplify by removing
__GL_SMALL_PTRDIFF_T__.
---
ChangeLog | 12 ++++++++++++
lib/obstack.in.h | 23 ++++++++++++++++-------
m4/obstack.m4 | 23 +----------------------
3 files changed, 29 insertions(+), 29 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 7448c09ebc..cc7e7e3256 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
2025-05-05 Paul Eggert <egg...@cs.ucla.edu>
+ obstack: use presence of uintptr_t
+ The code depends on the presence of uintptr_t,
+ not on whether ptrdiff_t is narrower than a pointer,
+ so use C macros that reflect this.
+ Also, clean up the namespace in the typical GCC-like case
+ * lib/obstack.in.h (_OBSTACK_UINTPTR_TYPE): New macro.
+ Include <stdint.h> only if needed (i.e., not GCC-like).
+ (__PTR_ALIGN): Use new macro instead of relying on
+ __GL_SMALL_PTRDIFF_T__ and directly on uintptr_t.
+ * m4/obstack.m4 (gl_FUNC_OBSTACK): Simplify by removing
+ __GL_SMALL_PTRDIFF_T__.
+
obstack: define PTR_INT_TYPE
* lib/obstack.in.h (PTR_INT_TYPE): Define, for compatibility
with glibc even though we don’t need the type for anything
diff --git a/lib/obstack.in.h b/lib/obstack.in.h
index 6b51ebde5d..aacd29edb4 100644
--- a/lib/obstack.in.h
+++ b/lib/obstack.in.h
@@ -125,7 +125,17 @@
# define PTR_INT_TYPE ptrdiff_t
#endif
-#include <stdint.h> /* For uintptr_t. */
+/* An integer type wide enough to hold a pointer value,
+ if such a type is available. */
+#ifdef __UINTPTR_TYPE__
+# define _OBSTACK_UINTPTR_TYPE __UINTPTR_TYPE__
+#elif defined __STDC_VERSION__ && 199901L <= __STDC_VERSION__
+# include <stdint.h>
+# ifdef UINTPTR_MAX
+# define _OBSTACK_UINTPTR_TYPE uintptr_t
+# endif
+#endif
+
#include <string.h> /* For memcpy, size_t. */
/* These macros highlight the places where this implementation
@@ -144,18 +154,17 @@
# define _OBSTACK_CHUNK_CONTENTS_SIZE 4
#endif
-/* __PTR_ALIGN(B, P, A) returns the result of aligning P to the next multiple
- of A + 1. B must be the base of an object addressed by P. B and P must be
- of type char *. A + 1 must be a power of 2.
- If ptrdiff_t is narrower than a pointer (e.g., the AS/400), play it
+/* If B is the base of an object addressed by P, return the result of
+ aligning P to the next multiple of A + 1. B and P must be of type
+ char *. A + 1 must be a power of 2. With no uintptr_t, play it
safe and compute the alignment relative to B. Otherwise, use the
faster strategy of computing the alignment through uintptr_t. */
-#if defined __GL_SMALL_PTRDIFF_T__
+#ifndef _OBSTACK_UINTPTR_TYPE
# define __PTR_ALIGN(B, P, A) \
((B) + (((P) - (B) + (A)) & ~(A)))
#else
# define __PTR_ALIGN(B, P, A) \
- ((P) + ((- (uintptr_t) (P)) & (A)))
+ ((P) + ((- (_OBSTACK_UINTPTR_TYPE) (P)) & (A)))
#endif
#ifndef __attribute_pure__
diff --git a/m4/obstack.m4 b/m4/obstack.m4
index 60948c9d5c..15f667332a 100644
--- a/m4/obstack.m4
+++ b/m4/obstack.m4
@@ -1,5 +1,5 @@
# obstack.m4
-# serial 1
+# serial 2
dnl Copyright 1996-2025 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -48,25 +48,4 @@ AC_DEFUN([gl_FUNC_OBSTACK]
GL_GENERATE_OBSTACK_H=false
fi
AC_SUBST([REPLACE_OBSTACK])
-
- dnl Test whether a 'ptrdiff_t' has at least as many bits as a pointer.
- AC_CACHE_CHECK([whether ptrdiff_t is at least as large as a pointer],
- [gl_cv_ptrdiff_t_wide_enough],
- [AC_COMPILE_IFELSE(
- [AC_LANG_PROGRAM(
- [[#include <stddef.h>
- typedef int check[2 * (sizeof (ptrdiff_t) >= sizeof (void *)) - 1];
- ]],
- [[]])],
- [gl_cv_ptrdiff_t_wide_enough=yes],
- [gl_cv_ptrdiff_t_wide_enough=no])
- ])
- if test $gl_cv_ptrdiff_t_wide_enough = yes; then
- SMALL_PTRDIFF_T=0
- else
- SMALL_PTRDIFF_T=1
- fi
- dnl SMALL_PTRDIFF_T is expected to be 1 only on old / exotic platforms
- dnl such as Windows 3.1 and AS/400.
- AC_SUBST([SMALL_PTRDIFF_T])
])
--
2.49.0
