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[Bug-readline] Memory leaks (identified with valgrind)

From: Timothe Litt
Subject: [Bug-readline] Memory leaks (identified with valgrind)
Date: Sun, 6 Mar 2016 07:56:55 -0500
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

readline 6.3 under Fedora Linux.
(same failures with 6.2)

Any trivial program using readline leaks memory. 
There is also a reference to uninitialized memory.

A sample distilled from a real application is included.

With no valgrindrc or leaker.history:

 cc -o rl_leaker -g rl_leaker.c -lreadline -ltermcap &&  \
    valgrind --gen-suppressions=all --show-leak-kinds=all \
    --leak-check=full ./rl_leaker 2>leaker63.txt

Without (even) doing any line editing:

To the prompt, type "hello readline"
To the next prompt, type "q"

==1841== HEAP SUMMARY:
==1841==     in use at exit: 76,701 bytes in 176 blocks
==1841==   total heap usage: 276 allocs, 100 frees, 87,744 bytes allocated

grep match-leak-kinds leaker63.txt

reveals that all the leaks are reachable.

I suggest that readline establish an "atexit" function during initialization
that will cleanup... or  (less desirable) provide a suitable function
for the
application to call "atexit".

Obviously, further testing with more user interaction is in order.

/* Demonstrate memory leaks in readline */

/* cc -o rl_leaker -g rl_leaker.c -lreadline -ltermcap && \
 * valgrind --gen-suppressions=all --show-leak-kinds=all \
 *    --leak-check=full ./rl_leaker 2>leaker.txt

#include <stdlib.h>
#include <stdio.h>

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

int main( int argc, char **argv ) {
    const char *hfname = "leaker.history";
    char *cmd;

    (void) argc;
    (void) argv;

    printf( "Readline version %s\n", rl_library_version );

    rl_readline_name = "leaker";
    history_truncate_file( hfname, 200 );
    stifle_history( 200 );
    read_history( hfname );

    do {
        char c;

        cmd = readline( "more> " );
        if( cmd == NULL ) break;

        if( *cmd != '\0' && *cmd != 'q' )
            add_history( cmd );
        printf( "less: %s\n", cmd );
        c = *cmd;
        free( cmd );
        if( c == 'q' ) break;
    } while( 1 );

    write_history( hfname );


The following suppression rules can mask the issue, but are unwise:
   <Readline senmdsg>

Timothe Litt
ACM Distinguished Engineer
This communication may not represent the ACM or my employer's views,
if any, on the matters discussed. 

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