Re: Discussion about why GNU/Linux system upgrades cause old programs to break

Arsen Arsenović <[email protected]> Fri, 14 Aug 2026 00:13:53 +0200

Newsgroups	gmane.emacs.devel
Message-ID	<[email protected]>

Eli Zaretskii <[email protected]> writes:

>> From: Arsen Arsenović <[email protected]>
>> Cc: [email protected],  [email protected]
>> Date: Wed, 12 Aug 2026 20:34:59 +0200
>> 
>> > Does Emacs 27 specify an option that implies "reject K&R syntax"
>> > or "complain about anything that doesn't satisfy the C99 spec?"
>> 
>> Yes, it will specifically pass -std=gnu11 to a C89 compiler:
>> 
>>   /tmp/emacs-27.1$ ./configure CC='gcc -std=gnu89' --with-jpeg=no --with-gif=no
>>   [...]
>>     What compiler should emacs be built with?               gcc -std=gnu89 -std=gnu11 -g3 -O2
>>   [...]
>
> Correction: the -std=gnu11 option will be passed to the compiler only
> if needed and supported.  Emacs (starting from v25.1) requires C99, it
> does not require C11.

That doesn't contradict what I said.

>> > Does GCC offer an option to allow K&R function definitions along with
>> > the features of C99, which could have been used in compiling Emacs 27?
>> 
>> Yes, though Emacs 27 doesn't need it, by passing -std=c89.
>> 
>> But, gcc allows you to recover the old behavior (of permitting cetain
>> K&R constructs in C99 and onwards) also, by passing:
>> 
>>   -Wno-error=implicit-function-declaration
>>   -Wno-error=declaration-missing-parameter-type
>>   -Wno-error=return-mismatch
>>   -Wno-error=int-conversion
>>   -Wno-error=incompatible-pointer-types
>
> Sadly, the GCC manual, even the latest one which ships with GCC 16.2,
> does not have an index entry that matches "K&R", so users who want to
> know how to disable the warnings and errors when compiling such
> programs have an uphill battle to fight to discover these options.

Indeed, it may be worth writing a little bit about that and linking to
the flag under (gcc) Standards, and then indexing the paragraph about
K&R C as such.

>> Emacs 27 builds fine actually.
>> 
>> The error that was originally being discussed was not a break in the
>> toolchain, just a system administration error.
>
> The problem with SIGSTKSZ, which breaks the original Emacs 27.1
> sources, is not a system administration error.  But yes, Emacs 27
> doesn't have problems with K&R syntax, that was a misunderstanding.

-- 
Arsen Arsenović

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