Re: git: d58339f39874 - main - tzcode: Drop libc namespace

Konstantin Belousov <kostikbel@gmail.com> writes:
> Dag-Erling Smørgrav <des@FreeBSD.org> writes:
> > If we really want to do what you suggest, there are better
> > ways (like what macOS does).
> I have no idea about MacOS/what is used by Mach-O.  Can you provide some
> hints or links, please?

They use macros in the header that contains the prototype to rename
functions when there are multiple variants.  In our case it would look
like this:

(in sys/sys/cdefs.h)

    #ifdef __LIBC
    #define __LIBC_SYM(sym) __asm("_" #sym)
    #else
    #define __LIBC_SYM(sym)
    #endif __LIBC

(in include/fcntl.h)

    int     open(const char *, int, ...) __LIBC_SYM(open);

(in lib/lib{c,sys,thr}/Makefile)

    CFLAGS+=-D__LIBC

This allows code in libc to use open() instead of _open() and not have
to worry about needing to include "namespace.h" and "un-namespace.h" in
the right places.  It also means simply adding __LIBC to any prototype
(and a __weak_reference in the correct place) automatically protects
every call to that function in lib{c,sys,thr} without having to chase
them all down.

DES
-- 
Dag-Erling Smørgrav - des@FreeBSD.org