This was clearly copied from a previous line but wasn't updated with the
correct condition to check, so if malloc() failed, it would dereference NULL
instead of reporting an error.
(transplanted from 1dc6e265fefcc1fec8d68f096a73e1dca4bf0691)
So if a zip file goes to the zip archiver but is corrupted, the system can now
know not to bother trying other archivers once the zip archiver has had a shot
at it, and just as important: it can report the real error from that archiver
instead of a generic "unsupported."
Now callbacks can stop further enumeration and report errors, if they had a
catastrophic issue or just found what they needed and don't need to process
any more items.
Also, the actual enumerators can report errors instead of silently dropping
items. This led to several other fixes as all these implementations got
audited and reworked.
The original, non-callback enumerator now returns NULL if it can't produce a
complete list instead of dropping items and returning a partial list.
So now you can drop this into your program and not worry about filename
conflicts, or where "platform_unix.c" came from in the debugger, etc.
Also renamed the "beos" sources to "haiku" and "macosx" to "macos" to match
modern platform names.
Ryan C. Gordon