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

Fri, 1 Mar 2002 10:47:33 -0600

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 it is obsolete because -1 is a valid address (255.255.255.255), and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?
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