Re: ANSI C standard of zsh

[Clinton Bunch <cdb_zsh@xxxxxxxxxxx>]

On 3/28/2024 04:16, Jun T wrote:
> > 2024/03/27 8:16、Clinton Bunch <cdb_zsh@xxxxxxxxxxx>のメール:
> >
> > If we're going to say Zsh expects C99 we should probably update
> > autoconf to check for C99 (and set any options needed)
> >
> > I've attached a patch for the trivial change needed.
> in the attached patch:
> > -AC_PROG_CC
> > +AC_PROG_CC_C99
> We can use AC_PROG_CC_C99 with autoconf-2.69, but in 2.7x
> it became obsolete and we need to use AC_PROG_CC, which
> tries C11, C99 and C89 (in this order) to find the latest
> edition the compiler supports.
>
> So we first need to decide which version of autoconf we
> use. Maybe we will continue using 2.69 for the moment?

EL 8 and 9 still ship 2.69, as does Solaris 11

FreeBSD 13.2-RELEASE-p10 has 2.71

The development guide currently says 2.50 or later.

2.71 is copyright 2021. 2.69 is 2012.

I believe in updating versions when they become too limiting, but 3 
years isn't what I'd consider limiting.  I don't think we should change 
to assume 2.71 yet.


Do we need to know that the compiler supports C11 unless we're using C11 
features?


> The following is info for someone who wants to know
> what AC_PROG_CC_C99 will check.
> In the comment to the AC_PROG_CC_C99 macro in c.m4
> (may be in /usr/share/autoconf/autoconf/ if you have 2.69
> installed, or lib/autoconf/ in the autoconf source tree):
>
> # It (AC_PROG_CC_C99) considers the compiler to be in ISO C99
> # mode if it handles
> # _Bool,
> # // comments,
> # flexible array members,          # aka incomplete array
> # inline,
> # long long int,
> # mixed code and declarations,
> # named initialization of structs, # aka designated initializer
> # restrict,
> # va_copy,                  # with <stdarg.h> and va_start etc.
> # varargs macros,        # macros with variable number of args
> # variable declarations in for loops      # for(int i=0; ...)
> # variable length arrays
>
> Note that "variable length array" (optional in C11) is
> required.
The current development guide specifically mentions support for variable 
length arrays.
> AC_PROG_CC_C99 does not check, for example (not comprehensive):
> headers other than <stdarg.h>, i.e., <complex.h>, <stdbool.h>,
>     <tgmath.h>, <intypes.h>, etc.
> snprintf() (and any other new library functions)
> universal character name: \uNNNN, \UNNNNNNNN
> compound literal