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bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9
From: |
Po Lu |
Subject: |
bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9 |
Date: |
Fri, 19 May 2023 08:46:02 +0800 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
Paul Eggert <eggert@cs.ucla.edu> writes:
> There would be problems in doing that. GCC and Clang both have
> problems with _Generic (suggested by this original bug report), and
> some of them have to do with which warnings you've enabled. The
> configure-time check would run without the warnings whereas the build
> would run with them.
>
> This is partly why intprops-internal.h has given up on _Generic with
> GCC and Clang; see its ifdefs. I assumed that these problems didn't
> apply to their simple use in elogb, but apparently I assumed
> incorrectly.
[...]
>> Btw, couldn't the macro be defined to something along the lines of this
>> when the compiler only supports C99?
>> #define foo(expression) \
>> (sizeof (expression) == sizeof (signed char) \
>
> That wouldn't work on unusual platforms that have padding bits. Of
> course we could simply refuse to port to targets like that; still, I'd
> be reluctant to do that just for this little issue.
How does intprops.h work on such systems?
> I couldn't measure the slowdown in this case. Until it's measurable I
> wouldn't worry about it. To some extent I put in that _Generic
> originally more as documentation than as an actual attempt to speed
> things up.
OK, but that's the second use of `long long' in src/ outside of
NT-specific files. I can't help but be a little skittish.
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Spencer Baugh, 2023/05/17
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Eli Zaretskii, 2023/05/17
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Paul Eggert, 2023/05/17
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Paul Eggert, 2023/05/18
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9,
Po Lu <=
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Paul Eggert, 2023/05/18
- bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Po Lu, 2023/05/18
bug#63556: 29.0.90; Use of _Generic breaks Emacs build on GCC <4.9, Paul Eggert, 2023/05/18