Provide a real feature test for __attribute__().

Looking at version numbers like __GNUC__ is always a bad idea.
Believe it or not, this even makes ./configure shorter by one line.

4 files changed, 57 insertions, 8 deletions

diff --git a/Makefile b/Makefile
index 80882eea..181014fb 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-# $Id: Makefile,v 1.534 2020/06/15 16:58:24 schwarze Exp $
+# $Id: Makefile,v 1.535 2020/06/22 20:00:38 schwarze Exp $
 #
 # Copyright (c) 2011, 2013-2020 Ingo Schwarze <schwarze@openbsd.org>
 # Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
@@ -19,7 +19,8 @@ VERSION = 1.14.5
 
 # === LIST OF FILES ====================================================
 
-TESTSRCS	 = test-be32toh.c \
+TESTSRCS	 = test-attribute.c \
+		   test-be32toh.c \
 		   test-cmsg.c \
 		   test-dirent-namlen.c \
 		   test-EFTYPE.c \
diff --git a/configure b/configure
index dbd7762a..1b1a5755 100755
--- a/configure
+++ b/configure
@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# $Id: configure,v 1.75 2020/06/15 01:37:15 schwarze Exp $
+# $Id: configure,v 1.76 2020/06/22 20:00:38 schwarze Exp $
 #
 # Copyright (c) 2014-2020 Ingo Schwarze <schwarze@openbsd.org>
 #
@@ -55,6 +55,7 @@ BUILD_CGI=0
 BUILD_CATMAN=0
 INSTALL_LIBMANDOC=0
 
+HAVE_ATTRIBUTE=
 HAVE_CMSG=
 HAVE_DIRENT_NAMLEN=
 HAVE_EFTYPE=
@@ -294,6 +295,7 @@ fi
 # --- tests for config.h  ----------------------------------------------
 
 # --- library functions ---
+runtest attribute	ATTRIBUTE	|| true
 runtest cmsg		CMSG		"" "-D_XPG4_2" || true
 runtest dirent-namlen	DIRENT_NAMLEN	|| true
 runtest be32toh		ENDIAN		|| true
@@ -422,10 +424,6 @@ cat << __HEREDOC__
 #error "Do not use C++.  See the INSTALL file."
 #endif
 
-#if !defined(__GNUC__) || (__GNUC__ < 4)
-#define __attribute__(x)
-#endif
-
 __HEREDOC__
 
 [ ${NEED_GNU_SOURCE} -eq 0 ] || echo "#define _GNU_SOURCE"
@@ -447,6 +445,7 @@ echo "#define OSENUM ${OSENUM}"
 [ -n "${OSNAME}" ] && echo "#define OSNAME \"${OSNAME}\""
 [ -n "${UTF8_LOCALE}" ] && echo "#define UTF8_LOCALE \"${UTF8_LOCALE}\""
 [ -n "${HOMEBREWDIR}" ] && echo "#define HOMEBREWDIR \"${HOMEBREWDIR}\""
+[ ${HAVE_ATTRIBUTE} -eq 0 ] && echo "#define __attribute__(x)"
 [ ${HAVE_EFTYPE} -eq 0 ] && echo "#define EFTYPE EINVAL"
 [ ${HAVE_O_DIRECTORY} -eq 0 ] && echo "#define O_DIRECTORY 0"
 [ ${HAVE_PATH_MAX} -eq 0 ] && echo "#define PATH_MAX 4096"
diff --git a/configure.local.example b/configure.local.example
index bfb2e3fd..63f16865 100644
--- a/configure.local.example
+++ b/configure.local.example
@@ -1,4 +1,4 @@
-# $Id: configure.local.example,v 1.37 2020/02/05 15:12:11 schwarze Exp $
+# $Id: configure.local.example,v 1.38 2020/06/22 20:00:38 schwarze Exp $
 #
 # Copyright (c) 2014-2019 Ingo Schwarze <schwarze@openbsd.org>
 #
@@ -288,6 +288,7 @@ CFLAGS="-g"
 # and will be regarded as failed) or 1 (test will not be run and will
 # be regarded as successful).
 
+HAVE_ATTRIBUTE=0
 HAVE_DIRENT_NAMLEN=0
 HAVE_ENDIAN=0
 HAVE_EFTYPE=0
diff --git a/test-attribute.c b/test-attribute.c
new file mode 100644
index 00000000..adbcc926
--- /dev/null
+++ b/test-attribute.c
@@ -0,0 +1,48 @@
+/* $Id: test-attribute.c,v 1.1 2020/06/22 20:00:38 schwarze Exp $ */
+/*
+ * Copyright (c) 2020 Ingo Schwarze <schwarze@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void	 var_arg(const char *, ...)
+		__attribute__((__format__ (__printf__, 1, 2)));
+void	 no_ret(int)
+		__attribute__((__noreturn__));
+
+void
+var_arg(const char *fmt, ...)
+{
+	va_list	 ap;
+
+	va_start(ap, fmt);
+	vprintf(fmt, ap);
+	va_end(ap);
+}
+
+void
+no_ret(int i)
+{
+	exit(i);
+}
+
+int
+main(void)
+{
+	var_arg("Test output: %d\n", 42);
+	no_ret(0);
+}