c99 support

c99 support

[Andy Wingo]

Hi,

Is there anyone who compiles Guile with a compiler that does not support
C99?  If so, please give platform and compiler.

I think my questions are limited to, in decreasing order of importance:

  * Is there any system that we target that doesn't have C99 stdint.h
    and stddef.h ?

  * Is there any system that we target that doesn't support C99 inline
    functions?

  * C99 mixed decls and statements?

  * C99 one-line comments (// foo) ?

  * C99 compound literals? ((struct x) { 1, 2 }) ?

  * stdbool.h

I would like to use C99 inside Guile, and I want to eventually replace
scm_t_uint8 with uint8_t.

Thanks,

Andy

Re: c99 support

[Chris Vine]

On Sat, 23 Jun 2018 22:12:39 +0200
Andy Wingo <wingo@pobox.com> wrote:
> Hi,
> 
> Is there anyone who compiles Guile with a compiler that does not support
> C99?  If so, please give platform and compiler.
> 
> I think my questions are limited to, in decreasing order of importance:
> 
>   * Is there any system that we target that doesn't have C99 stdint.h
>     and stddef.h ?
> 
>   * Is there any system that we target that doesn't support C99 inline
>     functions?
> 
>   * C99 mixed decls and statements?
> 
>   * C99 one-line comments (// foo) ?
> 
>   * C99 compound literals? ((struct x) { 1, 2 }) ?
> 
>   * stdbool.h
> 
> I would like to use C99 inside Guile, and I want to eventually replace
> scm_t_uint8 with uint8_t.

I include guile headers in C++11 code.  These C99 features seem to
be in current C++ (uint8_t is definitely supported if available on
the platform), except that my earlier assumption that compound literals
were in C++11 was wrong.  They do work, but that's because they are a
supported gcc, clang and MSVC extension in C++. That's decent coverage
though.

Although stdbool.h exists in C++11, its contents are signficantly
reduced in scope because bool is separately supported in C++.  The
definitions of bool are different in C99 and C++ - it is an integer type
plus macro in C99 - which might cause problems if the sizes of bool in
C++ and C99 are different.  It would be a very poor implementation which
does this, but stdbool.h may be best avoided in a guile header file.

This is not relevant if you are only including C99 features in
implementation (*.c) files.  That will always work OK.

Chris

Re: c99 support

[Eli Zaretskii]

> From: Andy Wingo <wingo@pobox.com>
> Cc: guile-users@gnu.org,  guile-devel@gnu.org
> Date: Sat, 23 Jun 2018 22:07:24 +0200
> 
> > MS-Windows (MinGW) doesn't have a C99 compliant C library, although
> > quite a few of what's needed is present.
> 
> Hard to say :)  I think my questions are limited to, in decreasing order
> of importance:
> 
>   * Is there any system that we target that doesn't have C99 stdint.h
>     and stddef.h ?
> 
>   * Is there any system that we target that doesn't support C99 inline
>     functions?
> 
>   * C99 mixed decls and statements?
> 
>   * C99 one-line comments (// foo) ?
> 
>   * C99 compound literals? ((struct x) { 1, 2 }) ?
> 
>   * stdbool.h

All of the above is available with reasonably recent versions of MinGW.

> I assume MinGW uses GCC.  What version?  I see that the version 6 series
> is available on mingw.org.

Current versions are 6 and 7, I have 5.3 installed on one of my
machines.  All of them support what you mentioned.

Re: c99 support

[Arne Babenhauserheide]

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Chris Vine <vine35792468@gmail.com> writes:

> On Sat, 23 Jun 2018 22:12:39 +0200
> Andy Wingo <wingo@pobox.com> wrote:
>> Hi,
>> 
>> Is there anyone who compiles Guile with a compiler that does not support
>> C99?  If so, please give platform and compiler.
>> 
>> I think my questions are limited to, in decreasing order of importance:
>> 
>>   * Is there any system that we target that doesn't have C99 stdint.h
>>     and stddef.h ?
>> 
>>   * Is there any system that we target that doesn't support C99 inline
>>     functions?
>> 
>>   * C99 mixed decls and statements?
>> 
>>   * C99 one-line comments (// foo) ?
>> 
>>   * C99 compound literals? ((struct x) { 1, 2 }) ?
>> 
>>   * stdbool.h
>> 
>> I would like to use C99 inside Guile, and I want to eventually replace
>> scm_t_uint8 with uint8_t.
>
> I include guile headers in C++11 code.  These C99 features seem to
> be in current C++ (uint8_t is definitely supported if available on
> the platform), except that my earlier assumption that compound literals
> were in C++11 was wrong.  They do work, but that's because they are a
> supported gcc, clang and MSVC extension in C++. That's decent coverage
> though.

OpenIndiana requires GCC 4.4.4 to build, so if Guile should be usable
for Solaris/Illumos development, compatibility to that would be
important. 4.4.4 seems to already support major parts of C99, but I’m not
sure whether something is missing: https://gcc.gnu.org/c99status.html

https://wiki.illumos.org/display/illumos/How+To+Build+illumos#HowToBuildillumos-GCC

Best wishes,
Arne
-- 
Unpolitisch sein
heißt politisch sein
ohne es zu merken

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Re: c99 support

[Andy Wingo]

On Sat 23 Jun 2018 22:12, Andy Wingo <wingo@pobox.com> writes:

> Is there anyone who compiles Guile with a compiler that does not support
> C99?  If so, please give platform and compiler.
>
> I think my questions are limited to, in decreasing order of importance:
>
>   * Is there any system that we target that doesn't have C99 stdint.h
>     and stddef.h ?
>
>   * Is there any system that we target that doesn't support C99 inline
>     functions?
>
>   * C99 mixed decls and statements?
>
>   * C99 one-line comments (// foo) ?
>
>   * C99 compound literals? ((struct x) { 1, 2 }) ?
>
>   * stdbool.h
>
> I would like to use C99 inside Guile, and I want to eventually replace
> scm_t_uint8 with uint8_t.

Thanks all for the responses.  It would seem that the first four
features of C99 are OK for all platforms that we target, with the
following caveats:

 * We should avoid using C++ keywords (e.g. throw) in Guile API files.

 * We might want to avoid mixed decls and statements in inline functions
   in Guile API files.

We should probably avoid stdbool.h and compound literals, for C++
reasons.

In Guile 3.0 (master branch), the types "scm_t_uint8" and so on are now
deprecated.  My recommendation is that all users switch to use
e.g. "uint8_t", "ptrdiff_t", etc from <stdint.h> instead of the
scm_t_uint8, etc definitions that they are now using.  The definitions
are compatible on all systems, AFAIU, and on GNU, scm_t_uint8 has long
been a simple typedef for uint8_t.

If you make the change while targetting current Guile (2.2), then you'll
won't have deprecation warnings when 3.0 comes out.

Cheers,

Andy