Re: use of the uniquely NetBSD _OPENBSD_SOURCE vs something better?

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

> Date: Wed, 07 May 2025 11:24:41 -0700
> From: "Greg A. Woods" <woods%planix.ca@localhost>
> 
> There is no _OPENBSD_SOURCE on OpenBSD.  It is purely a NetBSD invention.

This serves to make it easier to port OpenBSD-specific code to NetBSD,
and mark the fact that it's OpenBSD-specific, without encouraging more
adoption of bad APIs.

> Shouldn't strtonum() likewise be protected by _NETBSD_SOURCE on NetBSD?

We are not exposing it by default in order to discourage its use.  You
should use strtoi(3) instead.  See the man page for details:
https://man.NetBSD.org/strtonum.3

> I see reallocarray() has also been added within the _OPENBSD_SOURCE as
> well, and I think it too should only be protected by _NETBSD_SOURCE.

We did not expose it by default in order to discourage its use, and to
encourage reallocarr(3) instead which fixes its issues.  See the man
pages for details: https://man.NetBSD.org/reallocarr.3
https://man.NetBSD.org/reallocarray.3

Unfortunately, POSIX.1-2024 adopted reallocarray despite the flaws
that make it barely more useful than -- and just as difficult to use
safely as -- realloc(3), so it is also exposed by the appropriate
_POSIX_C_SOURCE now.

> Notably strlcpy() and strlcat() are not protected by this unique
> _OPENBSD_SOURCE though they both were invented by and taken from
> OpenBSD.  Instead they are protected by _NETBSD_SOURCE.

Probably for hysterical raisins.  If we were doing it again, we might
use _OPENBSD_SOURCE, or, maybe we just wouldn't adopt strlcpy/strlcat
-- see the litany of warnings in the man page for details:
https://man.NetBSD.org/strlcpy.3

> (Maybe _NETBSD_SOURCE should be changed to __BSD_VISIBLE too?  There
> could be some confusion from that I guess given it would offer different
> symbols on different systems unless there's a _lot_ more coordination
> and cooperation between the system's developers!)

Absolutely not, that would break all kinds of code that already uses
_NETBSD_SOURCE, for no benefit.  It _might_ be plausible for
sys/featuretest.h to have

#ifdef __BSD_VISIBLE
#define _NETBSD_SOURCE
#endif

or something like that, but that is a high-risk change that needs to
be supported by a pkgsrc bulk build to consider, and it would need to
be accompanied by a justification.