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__.

diff --git a/ChangeLog b/ChangeLog
index 7448c09ebca51353e6140f0e34a8b41730c4954f..cc7e7e325603ce2776a174757aa46baa1b8bb605 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 2025-05-05  Paul Eggert  <eggert@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 6b51ebde5d8126047c141a6b6ebe1a74813725e6..aacd29edb4d9fc83e838d6ae8a3dd118c115331a 100644 (file)
--- 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 60948c9d5cc5778c773fe4598978bdd315b5dfae..15f667332a2faa812bb9157b9bbd0c44ba285d7a 100644 (file)
--- 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])
 ])