Port cleanup attribute to OpenBSD

The OpenBSD C compiler issues false alarms about strcpy, strcat, and
sprintf, and this messes up 'configure' when it tests for the cleanup
attribute.  Work around the problem by using __has_attribute directly.
Problem reported by Joakim Jalap (Bug#22385).
* configure.ac: Don’t use AX_GCC_VAR_ATTRIBUTE.
* m4/ax_gcc_var_attribute.m4: Remove.
* src/conf_post.h (__has_attribute): Provide a substitute, for
non-GCC or older GCC compilers.  All uses changed to assume
the substitute.  Check for the cleanup attribute.
* src/emacs-module.c (module_has_cleanup): Just use __has_attribute.

2 files changed, 18 insertions, 13 deletions

diff --git a/src/conf_post.h b/src/conf_post.h
index 98ff12e5a53..5c332a05a5c 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -51,10 +51,21 @@ typedef bool bool_bf;
 #endif
 #endif
 
-/* When not using Clang, assume its attributes and features are absent.  */
+/* Simulate __has_attribute on compilers that lack it.  It is used only
+   on arguments like alloc_size that are handled in this simulation.  */
 #ifndef __has_attribute
-# define __has_attribute(a) false
-#endif
+# define __has_attribute(a) __has_attribute_##a
+# define __has_attribute_alloc_size (4 < __GNUC__ + (3 <= __GNUC_MINOR__))
+# define __has_attribute_cleanup (3 < __GNUC__ + (4 <= __GNUC_MINOR__))
+# define __has_attribute_externally_visible \
+    (4 < __GNUC__ + (1 <= __GNUC_MINOR__))
+# define __has_attribute_no_address_safety_analysis false
+# define __has_attribute_no_sanitize_address \
+    (4 < __GNUC__ + (8 <= __GNUC_MINOR__))
+#endif
+
+/* Simulate __has_feature on compilers that lack it.  It is used only
+   to define ADDRESS_SANITIZER below.  */
 #ifndef __has_feature
 # define __has_feature(a) false
 #endif
@@ -222,9 +233,7 @@ extern int emacs_setenv_TZ (char const *);
 #define NO_INLINE
 #endif
 
-#if (__clang__                                                          \
-     ? __has_attribute (externally_visible)                             \
-     : (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)))
+#if __has_attribute (externally_visible)
 #define EXTERNALLY_VISIBLE __attribute__((externally_visible))
 #else
 #define EXTERNALLY_VISIBLE
@@ -253,9 +262,7 @@ extern int emacs_setenv_TZ (char const *);
 # define ATTRIBUTE_MALLOC
 #endif
 
-#if (__clang__                                  \
-     ? __has_attribute (alloc_size)             \
-     : 4 < __GNUC__ + (3 <= __GNUC_MINOR__))
+#if __has_attribute (alloc_size)
 # define ATTRIBUTE_ALLOC_SIZE(args) __attribute__ ((__alloc_size__ args))
 #else
 # define ATTRIBUTE_ALLOC_SIZE(args)
@@ -278,8 +285,7 @@ extern int emacs_setenv_TZ (char const *);
 /* Attribute of functions whose code should not have addresses
    sanitized.  */
 
-#if (__has_attribute (no_sanitize_address) \
-     || 4 < __GNUC__ + (8 <= __GNUC_MINOR__))
+#if __has_attribute (no_sanitize_address)
 # define ATTRIBUTE_NO_SANITIZE_ADDRESS \
     __attribute__ ((no_sanitize_address)) ADDRESS_SANITIZER_WORKAROUND
 #elif __has_attribute (no_address_safety_analysis)
diff --git a/src/emacs-module.c b/src/emacs-module.c
index b5e044e758f..79a077b3cb4 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -35,8 +35,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Feature tests.  */
 
-/* True if __attribute__ ((cleanup (...))) works, false otherwise.  */
-#ifdef HAVE_VAR_ATTRIBUTE_CLEANUP
+#if __has_attribute (cleanup)
 enum { module_has_cleanup = true };
 #else
 enum { module_has_cleanup = false };