Re: Fwd: GnuTLS 3.6.12 patch for OS X 10.9

[Paul Eggert]

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 address@hidden.

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 <address@hidden>
> Date: Mon, Feb 3, 2020 at 3:12 AM
> Subject: GnuTLS 3.6.12 patch for OS X 10.9
> To: <address@hidden>
>
> 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

gnutls.patch
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