On Monday I wrote:
> > to exclude other problems, we need to check it on a platform-by-platform
> > basis.
This is the situation on the various platforms:
* In C++ mode,
- either the C <stdbool.h> is used,
- or a C++ <stdbool.h> exists that
#include <cstdbool>
- or a C++ <stdbool.h> exists that #include <__config>,
and the latter does:
Linux: #include <features.h>
FreeBSD: #include <sys/endian.h>, #include <osreldate.h>
NetBSD: #include <sys/endian.h>
Windows store apps: #include <winapifamily.h>
Solaris: #include <sys/isa_defs.h>
else: #include <endian.h>
The latter includes various OS stuff, and should therefore be
avoided when possible. Since a compilation unit cannot be ISO C 23
and C++ at the same time, it is easy to achieve: Wrap the new
config.h additions in
#ifndef __cplusplus
...
#endif
* In C mode: <stdbool.h> does
AIX: #include <standards.h>, defines only macros
FreeBSD: self-contained
Haiku: self-contained
HP-UX: #include <sys/stdsyms.h>, defines only macros
macOS: self-contained
mingw: self-contained
Minix: self-contained
musl: self-contained
NetBSD: self-contained
OpenBSD: self-contained
Solaris 10: #include <sys/feature_tests.h> -> #include <sys/ccompile.h>, #include <sys/isa_defs.h>, defines only macros
Solaris 11: #include <sys/feature_tests.h>
So, in this case, it is OK to #include <stdbool.h>, since it
does not include header files with function declarations, only
header files with macro definitions.
Paul Eggert wrote:
> In the long run this problem will vanish, as in the long run config.h
> will do nothing (that's all that's needed for C23 and C++).
I agree.
> In the shorter run I think we'll be OK for C17 and earlier if we include
> <stdbool.h> on platforms where bool+true+false don't work out of the
> box, because (unlike some other .h files) stdbool.h doesn't tend to
> cause conflicts.
Yes. Based on the analysis above, this should work.
So, IIUC, what we should do, is:
- Determine GL_GENERATE_STDBOOL_H as in gnulib/m4/stdbool.m4,
- If it is true, add to <config.h> the lines
#ifndef __cplusplus
... current contents of gnulib/m4/stdbool.in.h ...
#endif
- Otherwise, test "$ac_cv_header_stdbool_h".
- If it is != 'yes', add to <config.h> the lines
#ifndef __cplusplus
#include <stdbool.h>
#endif
Bruno
