ttyname_r on Mac

[Simon Josefsson]

Note: this problem doesn't cause my any immediate problem, but it breaks
the daily build on Mac.  I don't think it is important to work on fixing
this, but someone finds it interesting.

There appears to be a ttyname_r signature bug, see:
http://autobuild.josefsson.org/gnulib/log-201004250717723515000.txt

g++ -DHAVE_CONFIG_H -I.  -DGNULIB_STRICT_CHECKING=1 -I. -I. -I.. -I./.. 
-I../gllib -I./../gllib -I/opt/local/include   -MT test-fcntl-h-c++.o -MD -MP 
-MF $depbase.Tpo -c -o test-fcntl-h-c++.o test-fcntl-h-c++.cc &&\
mv -f $depbase.Tpo $depbase.Po
../gllib/unistd.h:1463: error: invalid conversion from 'char* (*)(int, char*, 
size_t)' to 'int (*)(int, char*, size_t)'
make[4]: *** [test-fcntl-h-c++.o] Error 1

The relevant code and the 1463 line is:

,----
| #if 1
| /* Store at most BUFLEN characters of the pathname of the terminal FD is
|    open on in BUF.  Return 0 on success, otherwise an error number.  */
| # if !1
| _GL_FUNCDECL_SYS (ttyname_r, int,
|                   (int fd, char *buf, size_t buflen) _GL_ARG_NONNULL ((2)));
| # endif
> _GL_CXXALIAS_SYS (ttyname_r, int,
|                   (int fd, char *buf, size_t buflen));
| _GL_CXXALIASWARN (ttyname_r);
| #elif defined GNULIB_POSIXCHECK
| # undef ttyname_r
| # if HAVE_RAW_DECL_TTYNAME_R
| _GL_WARN_ON_USE (ttyname_r, "ttyname_r is not portable - "
|                  "use gnulib module ttyname_r for portability");
| # endif
| #endif
`----

/usr/include/unistd.h contains:

#if __DARWIN_UNIX03
int      ttyname_r(int, char *, size_t) __DARWIN_ALIAS(ttyname_r);
#else /* !__DARWIN_UNIX03 */
char    *ttyname_r(int, char *, size_t);
#endif /* __DARWIN_UNIX03 */

So it seems ttyname_r on older Mac OS X versions returned char*.

Should we define __DARWIN_UNIX03?  I'm not sure how well supported that
is.  /usr/include/sys/cdefs.h contains:

/*
 * The __DARWIN_ALIAS macros is used to do symbol renaming, 
 * they allow old code to use the old symbol thus maintiang binary 
 * compatability while new code can use a new improved version of the 
 * same function.
 *
 * By default newly complied code will actually get the same symbols
 * that the old code did.  Defining any of _APPLE_C_SOURCE, _XOPEN_SOURCE,
 * or _POSIX_C_SOURCE will give you the new symbols.  Defining _XOPEN_SOURCE
 * or _POSIX_C_SOURCE also restricts the avilable symbols to a subset of
 * Apple's APIs.
 *
 * __DARWIN_ALIAS is used by itself if the function signature has not
 * changed, it is used along with a #ifdef check for __DARWIN_UNIX03
 * if the signature has changed.  Because the __LP64__ enviroment
 * only supports UNIX03 sementics it causes __DARWIN_UNIX03 to be
 * defined, but causes __DARWIN_ALIAS to do no symbol mangling.
 */

#if !defined(__DARWIN_UNIX03)
#if defined(_APPLE_C_SOURCE) || defined(_XOPEN_SOURCE) || 
defined(_POSIX_C_SOURCE) || defined(__LP64_
_)
#if defined(_NONSTD_SOURCE)
#error "Can't define both _NONSTD_SOURCE and any of _APPLE_C_SOURCE, 
_XOPEN_SOURCE, _POSIX_C_SOURCE, 
or __LP64__"
#endif /* _NONSTD_SOURCE */
#define __DARWIN_UNIX03 1
#elif defined(_NONSTD_SOURCE)
#define __DARWIN_UNIX03 0
#else /* default */
#define __DARWIN_UNIX03 0
#endif /* _APPLE_C_SOURCE || _XOPEN_SOURCE || _POSIX_C_SOURCE || __LP64__ */
#endif /* !__DARWIN_UNIX03 */

#if __DARWIN_UNIX03 && !defined(__LP64__)
#define __DARWIN_ALIAS(sym) __asm("_" __STRING(sym) "$UNIX2003")
#else
#define __DARWIN_ALIAS(sym)
#endif

Maybe we want to define _APPLE_C_SOURCE?  I'm doing a gnulib build with
that flag enabled now to see if it fixes anything.

/Simon