[Python-Dev] inet_addr usage in Modules/socketmodule.c?

[Skip Montanaro]

According to the checkin comment for Modules/socketmodule.c v. 1.91:

    Port inet_ntoa and inet_aton to Windows:

    - fix unescaped newline in string literal
    - removed unused err variable
    - Windows doesn't have inet_aton; use inet_addr instead

However, in the man page for inet_addr it states:

    This is an obsolete interface to inet_aton, described immediately above;
    it is obsolete because -1 is a valid address (255.255.255.255), and
    inet_aton provides a cleaner way to indicate error return.

The reason I bring it up is that a request came in today to python-help
about python-2.2 on an SX supercomputer, which suggests that the code for
handling INADDR_NONE (and thus inet_addr()) is broken:

    I have compiled python-2.2 on an SX supercomputer which does not have
    inet_pton(). The emulated one in Modules/socketmodule.c is being used
    instead. The test for packed_addr against INADDR_NONE fails because:

    1) INADDR_NONE is 0xffffffff in SX #include file,
    2) long on SX is 8-bytes,
    3) inet_addr() returns -1 (0xffffffffffffffff) which is -1, but _not_
       INADDR_NONE. 

    Has this problem come up anywhere else with sizeof(long) == 8 and
    inet_addr() schizophrenia?

    I realize that this may be an OS implementation issue (should
    inet_addr() return -1 or INADDR_NONE) but what should/can be done (if
    anything) to the Python package in order to address this?

It seems to me the simplest thing to do is to force a "proper" definition of
INADDR_NONE with something like

    #ifdef INADDR_NONE
    #undef INADDR_NONE
    #endif
    #define INADDR_NONE ((in_addr_t)-1)

if it's not defined and in_addr_t is available.  The more correct thing
would seem to be to dump inet_addr in favor of inet_aton unless the latter
is unavailable.  

On the other hand, perhaps just the SX include files are busted and all that
has to happen is to override INADDR_NONE for that platform:

    #if defined(INADDR_NONE) && INADDR_NONE != ((in_addr_t)-1)
    #undef INADDR_NONE
    #define INADDR_NONE ((in_addr_t)-1)
    #endif

Unfortunately, my mastery of the C preprocessor, casts, and configure is
insufficient to determine without some experimentation on a platform I have
no acces to if either of these is a workable approach or if there is a
better approach that will work on the SX.

Your thoughts?

Skip