[Bug libc/14024] argp: mis-formatted --help output

["mark-sourceware at glines dot org" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14024

--- Comment #3 from Mark Glines <mark-sourceware at glines dot org> 2012-04-26 17:28:13 UTC ---
I've done some preliminary analysis of this issue.  It appears that
__argp_fmtstream_update attempts to insert leading whitespace to indent the
remainder of an option's description (argp/argp-fmtstream.c:131).  However,
when the buffer does not have enough space for the additional whitespace, the
whitespace is instead printed directly to the output stream
(argp/argp-fmtstream.c:144).

When the buffer contained previous data that had not been written to the output
stream yet, this results in the output being printed out of order, appearing
mis-formatted to the user.

It's not immediately clear how to solve this.  The issue seems to be that
__argp_fmtstream_update can insert data into the buffer, but has no means to
grow the buffer if necessary.  The normal means of growing the buffer
(__argp_fmtstream_ensure) is a caller of __argp_fmtstream_update.

One option to fix this would be to flush the formatted output from the buffer
(if any), and then try again.

A second option would be to allocate a larger buffer, either duplicating the
buffer-expansion code in __argp_fmtstream_ensure, or splitting it out into a
third function which both can use.

A third option would be to change __argp_fmtstream_update to return an int
(currently it returns void), and have it return the amount of formatted text in
this case, so that __argp_fmtstream_ensure can only write the formatted subset
of the data in the buffer.  This option seems like it would have a higher
impact, as __argp_fmtstream_update has multiple callers.


File names and line numbers in the above text are referring to the argp code as
it was in today's git, revision 0ac229c819afd15ba323838ba72d0a409f16acc4.

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