Leak in XKeysymToString

[Alan Coopersmith]

On 8/20/22 11:47, Thomas Dickey wrote:
> On Sat, Aug 20, 2022 at 09:51:42AM -0700, Alan Coopersmith wrote:
>> Thanks - while gitlab is our preferred method, when that's not possible,
>> we prefer using the xorg-devel mailing list (cc'ed) instead of trying to
>> guess which individual developer to contact.
>>
>> This bug has been previously reported, but no one has developed a good
>> fix yet - I don't know if many XKeysymToString callers keep references to
>> the returned pointers and would be broken if those pointers suddenly had a
>> different string or were invalid due to a realloc() call.
> 
> The manpage hints that callers should make a copy of the string,
> since that "static area" implies that the library overwrites the
> data for each call:
> 
>         The returned string is in a static area and must not be modified.  The
>         returned string is in the Host Portable Character Encoding.  If the
>         specified KeySym is not defined, XKeysymToString returns a NULL.

Okay, but we also document that Xlib is thread safe if XInitThreads() has
been called, so both the patch suggested here to keep a static pointer to
a malloc'ed buffer and my suggestion of a global static buffer fail since
calls in different threads would have a race condition over whose answer
got returned.   We'd at least need a thread-specific buffer, which it
doesn't look like we've done in Xlib so far.

-- 
         -Alan Coopersmith-                 alan.coopersmith at oracle.com
          Oracle Solaris Engineering - https://blogs.oracle.com/solaris