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[perl #128313] Memory leak in perl 5.24.0 when use re qw[strict] isused

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Dan Collins via RT
June 8, 2016 15:50
[perl #128313] Memory leak in perl 5.24.0 when use re qw[strict] isused
Message ID:
Confirmed in blead on linux.

Valgrind with --leak-check=full --show-leak-kinds=all reports several records of the type:

    ==9552== 7,339,416 bytes in 53,965 blocks are still reachable in loss record 651 of 651
    ==9552==    at 0x4C2AB5C: realloc (vg_replace_malloc.c:785)
    ==9552==    by 0x55BF69: Perl_safesysrealloc (util.c:274)
    ==9552==    by 0x5C83D1: Perl_sv_grow (sv.c:1602)
    ==9552==    by 0x5ED031: Perl_sv_catpvn_flags (sv.c:5414)
    ==9552==    by 0x60DD01: Perl_sv_vcatpvfn_flags (sv.c:11499)
    ==9552==    by 0x60CC6C: Perl_sv_vsetpvfn (sv.c:10834)
    ==9552==    by 0x604835: Perl_vnewSVpvf (sv.c:9448)
    ==9552==    by 0x604738: Perl_newSVpvf (sv.c:9433)
    ==9552==    by 0x52A809: S_handle_possible_posix (regcomp.c:14050)
    ==9552==    by 0x53246B: S_regclass (regcomp.c:15853)
    ==9552==    by 0x52287F: S_regatom (regcomp.c:12392)
    ==9552==    by 0x51D66D: S_regpiece (regcomp.c:11483)

I was able to minimize the test case to:

    use re qw[strict];
    my $s = 'aaa';
    my $ps = 'aa';
    while (1) {
        $s =~ /[^.]+$ps/;

The memory is allocated at 14050:

    ADD_POSIX_WARNING(p, "there must be a starting ':'");

The function will eventually return at 14498:


Leaving AV* warn_text not mortalized, since that doesn't happen until 14533:

    if (posix_warnings) {
        /* mortalize to avoid a leak with FATAL warnings */
        *posix_warnings = (AV *) sv_2mortal((SV *) warn_text);
    else {

A possible solution is to mortalize warn_text at every location where S_handle_possible_posix can return NOT_MEANT_TO_BE_A_POSIX_CLASS. This is a bit ugly since I had to copy/paste the code to each of 6 locations, but it's the only way I could get `make test` to pass. At first, I tried making warn_text mortal when it's first allocated, but that seemed to make it get freed too early.

No idea how to write a test for this.

via perlbug:  queue: perl5 status: new

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