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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: gcc and 'include'
Date: Mon, 30 Mar 2026 11:54:37 -0700
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Bart <bc@freeuk.com> writes:
[...]
> The rules may well be precise, but they can also allow for laxity in
> how code is written, and how strictly they are enforced by a compiler.
>
> That is why exactly the same program can pass with 0 warnings or
> errors, pass with some warnings, or fail with errors, depending on the
> options provided. So:
>
>   c:\cx>gcc mcc.c
>
>   c:\cx>gcc -Wall -Wextra -Wpedantic -O2 mcc.c 2>errors
>
> The first invocation compiled fine. The second generated thousands of
> warnings, for the same language standard. With -Werror, it would also
> fail.
  
Not the same language.  gcc with no "-std=..." option compiles the
GNU C dialect.  The default is "-std=gnuNN", where NN is 17 or 23
for recent versions of gcc.  That's reasonable if your code depends
on GNU extensions, but not if you want to make a point about the
C language as defined by the ISO standard(s).

If you care about the C language as defined by the ISO standard,
you should be using something like "-std=cNN -pedantic" (or
"-pedantic-errors"), where NN is the relevant edition of the
standard.

With "-Wall -Wextra", if you get "thousands of warnings", it's
because you asked for them.

You're complaining about gcc being lax, not about the C language
being lax.

Of course you know all this.

I think there is some laxity in ISO C's treatment of "inline",
some cases where one conforming implementation might successfully
handle a program and another might reject it.  I agree that's not
ideal.  But as a programmer, you can avoid it by understanding the
standard's rules for "inline" and writing portable code.  (And as
an implementer, you can either make a choice within the range of
options allowed by the standard, or you can make a non-conforming
implementation that does whatever you prefer.)

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */