glibc's getopt uses alloca to construct a linked list of possibilities
for an "ambiguous" long option. In gnulib, malloc should be used
instead. Providing for both cases complicates things a fair bit.
This patch rewrites ambiguous-option handling to use a boolean vector
instead of a linked list. There is then only one allocation that
might need freeing; in glibc it can honor __libc_use_alloca as usual,
and in gnulib we define __libc_use_alloca to always be false, so we
don't need ifdefs in the middle of the function. This should also be
slightly more efficient in the normal case of long options being fully
spelled out -- I think most people aren't even aware they _can_
sometimes abbreviate long options.
One interesting consequence is that the list of possibilities is now
printed in exactly the order they appear in the list of long options,
instead of the first possibility being shuffled to the end.
(The patch looks bigger than it really is because there's a fair bit
of reindentation and code rearrangement.)
* lib/getopt.c: When used standalone, define __libc_use_alloca
as always false and alloca to abort if called.
(process_long_option): Rewrite handling of ambiguous long options
to use a single boolean vector, not a linked list; use
__libc_use_alloca to decide whether to allocate this using alloca.