Re: How to get autoconf to respect CC="gcc -std=c89"?

Just just 

./configure CC=gcc CFLAGS=-std=c89

No patching needed. Simple.
-- 
Evgeny

On 5 October 2023 23:31:58 GMT+03:00, "Niels Möller" <[email protected]> wrote:
>Hi,
>
>I still intend GNU Nettle to work with a c89 compiler, and I've been
>testing for that by configuring with
>
>  ./configure CC='gcc -std=c89'
>
>This used to catch accidental use of more recent C language features,
>like declarations not at the start of a block.
>
>However, I just realized that with recent autoconf (I'm now using
>autoconf-2.71), AC_PROG_CC has become more helpful, and in this
>configuration it automatically changes CC to 'gcc -std=c89 -std=gnu11'.
>It's documented at
>https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.71/html_node/C-Compiler.html#index-AC_005fPROG_005fCC-1,
>
>  If necessary, options are added to CC to enable support for ISO
>  Standard C features with extensions, preferring the newest edition of
>  the C standard that is supported.
>
>I'm sure that is a very useful feature in most cases, and a natural
>extension of the ancient autoconf feature of automatically adding flags
>needed to enable c89 aka ANSI-C.
>
>However, it completely defeats this way of testing that the project can
>be built with a c89 ompiler.
>
>Is there some way of telling autoconf to be less helpful, and attempt to
>add options only when needed to enable some particular version (in my
>case c89, less conservative projects might want to target c99 in the
>same way), but not add anything to enable even later language features?
>
>An alternative but less general approach would be some hack to skip this
>magic in the specific case that the compiler is gcc and CC already
>includes some -std=* argument.
>
>I think similar concerns apply to AC_PROG_CXX, and maybe this kind of
>testing is more important there due to higher speed of C++ language
>changes.
>
>BTW, I suspect that there's a typo in the corresponding docs for
>AC_PROG_CXX, it says
>
>  After calling this macro, you can check whether the C++ compiler has
>  been set to accept standard C++ by inspecting the shell variable
>  ac_prog_cc_stdc.
>
>"ac_prog_cc_stdc" looks wrong, since that's for AC_PROG_CC, not AC_PROG_CXX?
>
>Regards,
>/Niels
>