Re: how to test for a prototype difference

[Nick Bowler]

Hello,

Some comments...

On 2014-05-16 02:33 +0200, Thomas Klausner wrote:
> Hi Eric!
> 
> On Wed, Apr 30, 2014 at 06:51:23PM -0600, Eric Blake wrote:
> > On 04/30/2014 06:12 PM, Thomas Klausner wrote:
[...]
> > > I'd like to test for the difference int <-> size_t in a configure
> > > script so I can get integer type/sign conversion-warnings free code on
> > > all these operating systems.
> > > 
> > > I'm however not sure how to do this. Does anyone have a suggestion?
[...]
> Here's what I came up with:
> AC_CACHE_CHECK([parameter type for backtrace()],
>   [am_cv_proto_backtrace_type],

The am_cv_ prefix is used by Automake so I suggest choosing a
different one.

>   [AC_COMPILE_IFELSE(
>     [AC_LANG_PROGRAM(
>       [[
> #include <execinfo.h>
> extern
> #ifdef __cplusplus
> "C"
> #endif
> size_t backtrace(void **addrlist, size_t len);
>       ]])
>     ],
>     [am_cv_proto_backtrace_type=size_t],
>     [am_cv_proto_backtrace_type=int])

So if the compilation fails for any reason, you set the type to int.
That could be OK in your case (depending how you use it) but it seems
a little weird to me.

>   ])
> AC_DEFINE_UNQUOTED([backtrace_t], [$am_cv_proto_backtrace_type],
>   [Define to return type for backtrace().])

Note that POSIX reserves identifiers ending in _t if you include any
header file, so you should normally avoid using that suffix in an
application.

Cheers,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)