Re the message forwarded below. First I don't see a copy of this message at
<https://lists.gnu.org/r/gnutls-devel/2015-02/index.html> so I'm taking the
liberty of copying the entire thing to gnutls-de...@gnu.org.
Second, your patch (attached) doesn't look right. config.h should not #define
__has_attribute because too much code (perhaps unwisely) defaults
__has_attribute to something other than just 0, and relies on doing this, and if
config.h defaults it to 0 then the code won't work. (The advice about defaulting
__has_attribute to 0 in https://clang.llvm.org/docs/LanguageExtensions.html is
wrong for GCC.)
Third, the proposed patch uses __has_attribute(__noreturn__) to decide whether
_Noreturn is supported, which doesn't sound right. I expect that Clang
historically has had modes in which __attribute__((__noreturn__)) worked and
_Noreturn didn't, or vice versa.
If you could let us know exactly when Clang supports _Noreturn and when it
doesn't (C++ vs C, which version of Clang, which other C preprocessor macros
matter?) we could come up with a better patch.
---------- Forwarded message ---------
From: Jeffrey Walton <noloa...@gmail.com>
Date: Mon, Feb 3, 2020 at 3:12 AM
Subject: GnuTLS 3.6.12 patch for OS X 10.9
To: <gnutls-de...@lists.gnutls.org>
Hi Everyone,
I'm working from the GnuTLS 3.6.12 release tarball on OS X 10.9.
The build is failing due to the handling of _Noreturn in config.h and
gl/_Noreturn.h. An example of the error is shown below.
The attached patch fixes the build. In the case of OS X 10.9 with
Clang, the compiler already knows what to do with
__attribute__((__noreturn__)). The machinery should not modify
anything.
gcc -DHAVE_CONFIG_H -I. -I.. -I./gl -I./gl -I./../lib/includes
-I./../lib/includes -I./../libdane/includes -I./../extra/includes
-I../src/libopts -I./libopts -I/usr/local/include -DNDEBUG
-fno-common -Wall -g2 -O2 -march=native -fPIC -pthread -MT tests.o
-MD -MP -MF $depbase.Tpo -c -o tests.o tests.c &&\
mv -f $depbase.Tpo $depbase.Po
In file included from psk.c:50:
In file included from ./gl/unistd.h:40:
/usr/include/unistd.h:424:18: error: use of undeclared identifier '__noreturn__'
void _exit(int) __dead2;
^
/usr/include/sys/cdefs.h:135:33: note: expanded from macro '__dead2'
#define __dead2 __attribute__((noreturn))
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/6.0/include/stdnoreturn.h:27:18:
note:
expanded from macro 'noreturn'
#define noreturn _Noreturn
^
../config.h:1828:37: note: expanded from macro '_Noreturn'
# define _Noreturn __attribute__ ((__noreturn__))
^
In file included from psk.c:50:
In file included from ./gl/unistd.h:40:
/usr/include/unistd.h:640:18: error: use of undeclared identifier '__noreturn__'
void _Exit(int) __dead2;
^
/usr/include/sys/cdefs.h:135:33: note: expanded from macro '__dead2'
#define __dead2 __attribute__((noreturn))
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/6.0/include/stdnoreturn.h:27:18:
note:
expanded from macro 'noreturn'
#define noreturn _Noreturn
^
../config.h:1828:37: note: expanded from macro '_Noreturn'
# define _Noreturn __attribute__ ((__noreturn__))
^
2 errors generated.
gmake[4]: *** [Makefile:2121: psk.o] Error 1
gmake[4]: *** Waiting for unfinished jobs....
If you don't like the use of __has_attribute, then the following
defines may be helpful to untangle things (or make the fur ball
bigger):
$ gcc -dM -E - < /dev/null | grep -i -E 'clang|llvm|apple|gnu'
#define __APPLE_CC__ 6000
#define __APPLE__ 1
#define __GNUC_MINOR__ 2
#define __GNUC_PATCHLEVEL__ 1
#define __GNUC_STDC_INLINE__ 1
#define __GNUC__ 4
#define __VERSION__ "4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)"
#define __apple_build_version__ 6000057
#define __clang__ 1
#define __clang_major__ 6
#define __clang_minor__ 0
#define __clang_patchlevel__ 0
#define __clang_version__ "6.0 (clang-600.0.57)"
#define __llvm__ 1
Jeff
--- config.h.in
+++ config.h.in
@@ -1806,9 +1806,16 @@
/* Define to 1 to make NetBSD features available. MINIX 3 needs this. */
#undef _NETBSD_SOURCE
+/* https://clang.llvm.org/docs/LanguageExtensions.html */
+#ifndef __has_attribute // Optional of course.
+# define __has_attribute(x) 0 // Compatibility non-clang compilers.
+#endif
+
/* The _Noreturn keyword of C11. */
#ifndef _Noreturn
-# if (defined __cplusplus \
+# if defined(__APPLE__) && defined(__clang__) && (__has_attribute(__noreturn__) == 1)
+ /* Don't do anything. Stay out of code paths below. */
+# elif (defined __cplusplus \
&& ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
|| (defined _MSC_VER && 1900 <= _MSC_VER)))
# define _Noreturn [[noreturn]]
--- src/gl/_Noreturn.h
+++ src/gl/_Noreturn.h
@@ -14,8 +14,15 @@
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
+/* https://clang.llvm.org/docs/LanguageExtensions.html */
+#ifndef __has_attribute // Optional of course.
+# define __has_attribute(x) 0 // Compatibility non-clang compilers.
+#endif
+
#ifndef _Noreturn
-# if (defined __cplusplus \
+# if defined(__APPLE__) && defined(__clang__) && (__has_attribute(__noreturn__) == 1)
+ /* Don't do anything. Stay out of code paths below. */
+# elif (defined __cplusplus \
&& ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
|| (defined _MSC_VER && 1900 <= _MSC_VER)))
# define _Noreturn [[noreturn]]
