Readline library crash on custom completion

Binary package hint: libreadline5

Description
=======

Using up-to-date feisty.

I am using libreadline to provide custom completion for an application.

Using custom completion involves setting a global C symbol
(rl_attempted_completion_function) to a function that returns with a list
of suitable matches:

char ** match_generator(char * prefix, ...);

The char ** result ends with a (char *)NULL. If no matches are found, this
returns the NULL on the first position which confuses readline (see patch).

Steps to reproduce:
============

/* compile: gcc -Wall -O -o rltest rltest.c -lreadline */

#include <stdlib.h>
#include <readline/readline.h>
#include <readline/history.h>

char ** match_func(const char * text, int start, int end)
{
        char ** ret = (char **)malloc(sizeof(char *));
        ret[0] = 0;
        return ret;
}

int main()
{
        rl_attempted_completion_over = 1;
        rl_attempted_completion_function = match_func;

        readline("hit TAB> ");
        return 0;
}

Fixes
====

Existing applications can simply do "if !matches[0] then matches=0".

To get expected (IMHO) behaviour from the library:

--- readline-5.2/complete.c 2006-07-28 17:35:49.000000000 +0200
+++ readline-5.2-fixed/complete.c 2007-07-27 16:57:02.000000000 +0200
@@ -961,6 +961,7 @@
   if (rl_attempted_completion_function)
     {
       matches = (*rl_attempted_completion_function) (text, start, end);
+ if (matches && ! matches[0]) matches = 0;

       if (matches || rl_attempted_completion_over)
        {

====

Cheers!