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Re: [PATCH] Use ^=1 to toggle between 0 and 1

From
René Scharfe <l.s.r@web.de>
Date
Dec 16, 2023, 10:46 UTC
Message-ID
<b3c0c52b-7e12-4068-99fd-07fe4fa3da7d@web.de>
In-Reply-To
<xmqqo7erl7er.fsf@gitster.g>
Am 15.12.23 um 18:09 schrieb Junio C Hamano:
Show 15 quoted lines
> Phillip Wood <phillip.wood123@gmail.com> writes:
>
>> Even if it unlikely that we would directly compare a boolean variable
>> to "true" or "false" it is certainly conceivable that we'd compare two
>> boolean variables directly. For the integer fallback to be safe we'd
>> need to write
>>
>> 	if (!cond_a == !cond_b)
>>
>> rather than
>>
>> 	if (cond_a == cond_b)
>
> Eek, it defeats the benefit of using true Boolean type if we had to
> train ourselves to write the former, doesn't it?
Indeed.
Show 23 quoted lines
>> [1] 7bc341e21b (git-compat-util: add a test balloon for C99 support,
>> 2021-12-01)
>
> Nice to be reminded of this one.
>
> The cited commit does not start to use any specific feature from
> C99, other than that we now require that the compiler claims C99
> conformance by __STDC_VERSION__ set appropriately.  The commit log
> message says C99 "provides a variety of useful features, including
> ..., many of which we already use.", which implies that our wish was
> to officially allow any and all features in C99 to be used in our
> codebase after a successful flight of this test balloon.
>
> Now, I think we saw a successful flight of this test balloon by now.
> Is allowing all the C99 the next step we really want to take?
>
> I still personally have an aversion against decl-after-statement and
> //-comments, not due to portability reasons at all, but because I
> find that the code is easier to read without it. But in principle,
> it is powerful to be able to say "OK, as long as the feature is in
> C99 you can use it", instead of having to decide on individual
> features, and I am not fundamentally against going that route if it
> is where people want to go.

C99 added a lot of features, but we already use several of them. Support for individual features may vary, though -- who knows?

E.g. http://www.compilers.de/vbcc.html claims to support "most of ISO/IEC 9899:1999 (C99)", yet _Bool is not mentioned in its docs (but __STDC_VERSION__ 199901L is). It's not a particularly interesting compiler for us, but still a real-world example of selective C99 support.

The table at the bottom of https://en.cppreference.com/w/c/99 would be useful if it was filled out for more compilers. And it also doesn't mention _Bool and stdbool.h.

TenDRA and the M/o/Vfuscator are the only compilers without stdbool.h support on https://godbolt.org/ as far as I can see, but that website doesn't have a lot of commercial compilers (understandably).

So I guess in practice we still need to check each new feature, even though in theory we should be fine after the two-year test.

René
Previous: Junio C HamanoNext: Phillip Wood
Message 11 of 26 in “Use ^=1 to toggle between 0 and 1”
  1. Use ^=1 to toggle between 0 and 1AtariDreams via GitGitGadget, Dec 12, 2023
  2. Dragan SimicDec 12, 2023
  3. Jeff KingDec 12, 2023
  4. René ScharfeDec 12, 2023
  5. Jeff KingDec 13, 2023
  6. Junio C HamanoDec 13, 2023
  7. René ScharfeDec 14, 2023
  8. Jeff KingDec 14, 2023
  9. Phillip WoodDec 15, 2023
  10. Junio C HamanoDec 15, 2023
  11. René ScharfeDec 16, 2023
  12. Phillip WoodDec 18, 2023
  13. git-compat-util: convert skip_{prefix,suffix}{,_mem} to boolRené Scharfe, Dec 16, 2023
  14. Phillip WoodDec 18, 2023
  15. Junio C HamanoDec 18, 2023
  16. René ScharfeDec 19, 2023
  17. Jeff KingDec 21, 2023
  18. Jeff KingDec 21, 2023
  19. phillip.wood123@gmail.comDec 21, 2023
  20. Use ^=1 to toggle between 0 and 1AreaZR via GitGitGadget, Dec 18, 2024
  21. git: use ^=1 to toggle between 0 and 1AreaZR via GitGitGadget, Dec 18, 2024
  22. git: use ^=1 to toggle between 0 and 1AreaZR via GitGitGadget, Dec 18, 2024
  23. git: use ^=1 to toggle between 0 and 1AreaZR via GitGitGadget, Dec 18, 2024
  24. git: use logical-not operator to toggle between 0 and 1AreaZR via GitGitGadget, Dec 18, 2024
  25. Junio C HamanoDec 19, 2024
  26. Junio C HamanoDec 18, 2024

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