Re: master 13c8cc58bb: Enable warnings when building as a developer with

Re: master 13c8cc58bb: Enable warnings when building as a developer with

[Paul Eggert]

> The impression I got from postings around here lead me to think that
> clang posing as an old GCC is something specific to macOS.
> Is that indeed the case?

No, clang poses as old GCC everywhere. If you run "clang -x c /dev/null 
-dM -E" on Fedora 35, you'll see:

#define __GNUC_MINOR__ 2
#define __GNUC_PATCHLEVEL__ 1
#define __GNUC_STDC_INLINE__ 1
#define __GNUC__ 4

and a bunch of other GCC-specific macros. As I understand it, the GCC 
developers have asked the Clang developers to not pretend to be GCC, but 
the Clang developers have ignored the request.

In my experience, if you enable warnings, Clang generates too many false 
alarms. In particular, I can't build Emacs with Clang and with 
--enable-gcc-warnings, because of the false alarms it generates. So I 
just now suggested privately to Mattias to revert that recent change to 
Emacs configure.ac, so that --enable-gcc-warnings is the default for 
developers only if they're using GCC. It's not worth our time to worry 
about the Clang warnings, since GCC warnings work as well or better.

Re: master 13c8cc58bb: Enable warnings when building as a developer with

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

Is there a way to distinguish Clang from GCC by running shell commands?
Autoconf could use that to provide a way to distinguish them.

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

Re: master 13c8cc58bb: Enable warnings when building as a developer with

[Po Lu]

Richard Stallman <rms@gnu.org> writes:

> Is there a way to distinguish Clang from GCC by running shell commands?
> Autoconf could use that to provide a way to distinguish them.

Yes, in fact we already do that in Emacs:

  # clang is unduly picky about some things.
  AC_CACHE_CHECK([whether the compiler is clang], [emacs_cv_clang],
    [AC_COMPILE_IFELSE(
       [AC_LANG_PROGRAM([[
            #ifndef __clang__
              error "not clang";
            #endif
          ]])],
       [emacs_cv_clang=yes],
       [emacs_cv_clang=no])])