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.

4 files changed, 18 insertions, 155 deletions

diff --git a/configure.ac b/configure.ac
index 8c01abac9c6..3aeba22ec47 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3327,7 +3327,6 @@ if test "${HAVE_MODULES}" = yes; then
 fi
 AC_SUBST(MODULES_OBJ)
 AC_SUBST(LIBMODULES)
-AX_GCC_VAR_ATTRIBUTE(cleanup)
 AC_CHECK_FUNCS(dladdr)
 
 ### Use -lpng if available, unless '--with-png=no'.
diff --git a/m4/ax_gcc_var_attribute.m4 b/m4/ax_gcc_var_attribute.m4
deleted file mode 100644
index d12fce8934e..00000000000
--- a/m4/ax_gcc_var_attribute.m4
+++ /dev/null
@@ -1,141 +0,0 @@
-# ===========================================================================
-#   http://www.gnu.org/software/autoconf-archive/ax_gcc_var_attribute.html
-# ===========================================================================
-#
-# SYNOPSIS
-#
-#   AX_GCC_VAR_ATTRIBUTE(ATTRIBUTE)
-#
-# DESCRIPTION
-#
-#   This macro checks if the compiler supports one of GCC's variable
-#   attributes; many other compilers also provide variable attributes with
-#   the same syntax. Compiler warnings are used to detect supported
-#   attributes as unsupported ones are ignored by default so quieting
-#   warnings when using this macro will yield false positives.
-#
-#   The ATTRIBUTE parameter holds the name of the attribute to be checked.
-#
-#   If ATTRIBUTE is supported define HAVE_VAR_ATTRIBUTE_<ATTRIBUTE>.
-#
-#   The macro caches its result in the ax_cv_have_var_attribute_<attribute>
-#   variable.
-#
-#   The macro currently supports the following variable attributes:
-#
-#    aligned
-#    cleanup
-#    common
-#    nocommon
-#    deprecated
-#    mode
-#    packed
-#    tls_model
-#    unused
-#    used
-#    vector_size
-#    weak
-#    dllimport
-#    dllexport
-#    init_priority
-#
-#   Unsupported variable attributes will be tested against a global integer
-#   variable and without any arguments given to the attribute itself; the
-#   result of this check might be wrong or meaningless so use with care.
-#
-# LICENSE
-#
-#   Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com>
-#
-#   Copying and distribution of this file, with or without modification, are
-#   permitted in any medium without royalty provided the copyright notice
-#   and this notice are preserved.  This file is offered as-is, without any
-#   warranty.
-
-#serial 3
-
-AC_DEFUN([AX_GCC_VAR_ATTRIBUTE], [
-    AS_VAR_PUSHDEF([ac_var], [ax_cv_have_var_attribute_$1])
-
-    AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [
-        AC_LINK_IFELSE([AC_LANG_PROGRAM([
-            m4_case([$1],
-                [aligned], [
-                    int foo __attribute__(($1(32)));
-                ],
-                [cleanup], [
-                    int bar(int *t) { return *t; };
-                ],
-                [common], [
-                    int foo __attribute__(($1));
-                ],
-                [nocommon], [
-                    int foo __attribute__(($1));
-                ],
-                [deprecated], [
-                    int foo __attribute__(($1)) = 0;
-                ],
-                [mode], [
-                    long foo __attribute__(($1(word)));
-                ],
-                [packed], [
-                    struct bar {
-                        int baz __attribute__(($1));
-                    };
-                ],
-                [tls_model], [
-                    __thread int bar1 __attribute__(($1("global-dynamic")));
-                    __thread int bar2 __attribute__(($1("local-dynamic")));
-                    __thread int bar3 __attribute__(($1("initial-exec")));
-                    __thread int bar4 __attribute__(($1("local-exec")));
-                ],
-                [unused], [
-                    int foo __attribute__(($1));
-                ],
-                [used], [
-                    int foo __attribute__(($1));
-                ],
-                [vector_size], [
-                    int foo __attribute__(($1(16)));
-                ],
-                [weak], [
-                    int foo __attribute__(($1));
-                ],
-                [dllimport], [
-                    int foo __attribute__(($1));
-                ],
-                [dllexport], [
-                    int foo __attribute__(($1));
-                ],
-                [init_priority], [
-                    struct bar { bar() {} ~bar() {} };
-                    bar b __attribute__(($1(65535/2)));
-                ],
-                [
-                 m4_warn([syntax], [Unsupported attribute $1, the test may fail])
-                 int foo __attribute__(($1));
-                ]
-            )], [
-            m4_case([$1],
-                [cleanup], [
-                    int foo __attribute__(($1(bar))) = 0;
-                    foo = foo + 1;
-                ],
-                []
-            )])
-            ],
-            dnl GCC doesn't exit with an error if an unknown attribute is
-            dnl provided but only outputs a warning, so accept the attribute
-            dnl only if no warning were issued.
-            [AS_IF([test -s conftest.err],
-                [AS_VAR_SET([ac_var], [no])],
-                [AS_VAR_SET([ac_var], [yes])])],
-            [AS_VAR_SET([ac_var], [no])])
-    ])
-
-    AS_IF([test yes = AS_VAR_GET([ac_var])],
-        [AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_VAR_ATTRIBUTE_$1), 1,
-            [Define to 1 if the system has the `$1' variable attribute])], [])
-
-    AS_VAR_POPDEF([ac_var])
-])
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 };