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

Niels Möller wrote:
> Paul Eggert <[email protected]> writes:
>
>   
>> This doesn't let you say "I want either c89 or c99, but not c11".
>>     
>
> That's right, I tried only the very simplest thing. Providing a list
> makes sense, thoguh. What should the interface be?
>
>   AC_C_STANDARD_VERSION([c99 c89])
>
> looks reasonable to me; list in order of preference, and whitespace
> separation. That's consistent with AC_PROG_CC. But that means that
>
>   AC_C_STANDARD_VERSION([c89 c99])
>
> is a bit meaningless; if compiler has c89, that's what will be used, and
> if it doesn't have c89, it won't have c99 either. 

Free compilers may behave that way, however I have vague memories of a 
compiler that dropped support for K&R function definitions many years 
ago, long before GCC did.  Since Autoconf seeks portability, including 
to non-free systems, preferring C89 but accepting C99 is reasonable to 
express.  There may be non-free compilers out there that do not accept 
C89 but do accept C99.

> [...]
> I considered trying this out, but then there's some impedance mismatch
> between the whitespace separated list to AC_C_STANDARD_VERSION, and the
> comma-separated list required by m4_map. Certainly doable, but what's
> the easiest way to transform
>
>   [c99 c89]
>
> into 
>   
>   [99, 89]
>
> ?
>   

Some quick tests here suggest that "patsubst(patsubst([c99 c89], [c]), [ 
], [, ])" should do that trick.

>>> +  m4_ifdef([_AC_C_STANDARD_VERSION_LIST],
>>> +    [m4_fatal([AC_PROG_C_STANDARD_VERSION should only be used once], 1)])
>>>       
>> Why have this check?
>>     
>
> I figured the user should get some error message if using
> AC_C_STANDARD_VERSION too late, e.g., after some AC_FOO that implicitly
> uses AC_PROG_CC, which will also trigger this check. Not sure of
> m4_fatal is the right way to signals error to the user, though. (And
> error message could be improved).
>   

How about "error:  AC_PROG_CC_STANDARD_EDITION used after AC_PROG_CC 
invoked"?


-- Jacob