The Oracle Developer Studio 12.6 produces a compilation error when
compiling the Gnulib module 'obstack':
cc -m64 -O -DHAVE_CONFIG_H -I. -I../../gllib -I.. -DGNULIB_STRICT_CHECKING=1
-I/home/haible/prefix64/include -g -c -o obstack.o ../../gllib/obstack.c
"../../gllib/obstack.c", line 119: internal compiler error:
ir_process_arrloc_tree: bad arrloc tree
cc: acomp failed for ../../gllib/obstack.c
gmake[3]: *** [Makefile:1028: obstack.o] Error 2
The Oracle support determined that the problem is that the compiler gets
confused by the conditional expression in the __PTR_ALIGN macro.
This patch provides a workaround: Let's evaluate the condition at
configure time, rather than at compile time.
2024-03-27 Bruno Haible <br...@clisp.org>
obstack: Work around ICE with Oracle cc 12.6 (regr. 2023-12-01).
* lib/obstack.in.h (__PTR_ALIGN): Use SMALL_PTRDIFF_T, instead of
testing sizeof (ptrdiff_t) < sizeof (void *) at compile time.
* m4/obstack.m4 (gl_FUNC_OBSTACK): Set SMALL_PTRDIFF_T.
* modules/obstack (Makefile.am): Substitute SMALL_PTRDIFF_T.
diff --git a/lib/obstack.in.h b/lib/obstack.in.h
index cf149947be..28fb4d8916 100644
--- a/lib/obstack.in.h
+++ b/lib/obstack.in.h
@@ -133,17 +133,19 @@
# define _OBSTACK_CAST(type, expr) (expr)
#endif
-/* 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.
+/* __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
safe and compute the alignment relative to B. Otherwise, use the
faster strategy of computing the alignment through uintptr_t. */
-
-#define __PTR_ALIGN(B, P, A) \
- (sizeof (ptrdiff_t) < sizeof (void *) \
- ? (B) + (((P) - (B) + (A)) & ~(A)) \
- : (P) + ((- (uintptr_t) (P)) & (A)))
+#if @SMALL_PTRDIFF_T@
+# define __PTR_ALIGN(B, P, A) \
+ ((B) + (((P) - (B) + (A)) & ~(A)))
+#else
+# define __PTR_ALIGN(B, P, A) \
+ ((P) + ((- (uintptr_t) (P)) & (A)))
+#endif
#ifndef __attribute_pure__
# define __attribute_pure__ _GL_ATTRIBUTE_PURE
diff --git a/m4/obstack.m4 b/m4/obstack.m4
index 196609d7fb..be553cfb78 100644
--- a/m4/obstack.m4
+++ b/m4/obstack.m4
@@ -45,4 +45,25 @@ 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])
])
diff --git a/modules/obstack b/modules/obstack
index e4db4cdc97..5c94894e8c 100644
--- a/modules/obstack
+++ b/modules/obstack
@@ -31,6 +31,7 @@ obstack.h: obstack.in.h $(top_builddir)/config.status
@NMD@ $(AM_V_GEN)$(MKDIR_P) '%reldir%'
$(gl_V_at)$(SED_HEADER_STDOUT) \
-e 's|@''REPLACE_OBSTACK''@|$(REPLACE_OBSTACK)|g' \
+ -e 's|@''SMALL_PTRDIFF_T''@|$(SMALL_PTRDIFF_T)|g' \
$(srcdir)/obstack.in.h > $@-t
$(AM_V_at)mv $@-t $@
else
