Re: [bug-gnulib] getlogin_r.m4 and host_os.m4

[Bruno Haible]

Paul Eggert wrote:
> the getlogin_r.m4 change (adding
> AC_REQUIRE([AC_GNU_SOURCE])) looks a bit GNU-specific.  Wouldn't it be
> better to depend on the 'extensions' module instead?  That would catch
> similar problems in non-GNU systems.
> 
> (Come to think of it, doesn't a similar argument apply to the 30 or so
> other uses of AC_GNU_SOURCE in gnulib?  I guess I can bring that up on
> a different thread....)

Traditionally, we use AC_GNU_SOURCE to get declarations on glibc systems,
and gl_USE_SYSTEM_EXTENSIONS to get declarations on glibc and Solaris
systems.

getlogin_r appears to have the same problem on Solaris as on glibc, says
a look into <unistd.h>. So it's good to use gl_USE_SYSTEM_EXTENSIONS in this
case.

memmem(), on the other hand, is not defined in Solaris headers. It's a
pure glibc invention. Checking whether to define __EXTENSIONS__ for using
memmem() would be pointless.

So IMO whether to use AC_GNU_SOURCE or 'extensions' needs to be decided
on a case by case basis.

Bruno