Hi all.

I'm working with a fleet of devices running Perl on a ARM chipset (armhf) that are experiencing an infrequent, random crash in SQL::Abstract (via DBIx::Class). I've not yet been able to reproduce it manually, our only clue to go off of has been the following log statement.

panic: stack_grow() negative count (-16777216) at /usr/share/perl5/SQL/Abstract.pm line 1493

I've found similar threads of https://rt-cpan.github.io/Public/Bug/Display/108578/ and https://github.com/Perl/perl5/issues/15013. But neither of which were fruitful.

My first observation was that -16777216 is 0xFF000000 as a 32-bit signed value. This makes me think it's due to a unsigned to signed cast gone wrong. However, adding 16 MiB to the stack seems incorrect as well. To me this screams memory corruption or an uninitialized value.

I ran it with the -d flag to get the following stack trace:

@ = SQL::Abstract::_join_sql_clauses(ref(DBIx::Class::SQLMaker), 'and'
+, ref(ARRAY), ref(ARRAY)) called from file '/usr/share/perl5/SQL/Abst
+ract.pm' line 678
@ = SQL::Abstract::_where_HASHREF(ref(DBIx::Class::SQLMaker), ref(HASH
+), undef) called from file '/usr/share/perl5/SQL/Abstract.pm' line 54
+5
@ = SQL::Abstract::_recurse_where(ref(DBIx::Class::SQLMaker), ref(HASH
+)) called from file '/usr/share/perl5/SQL/Abstract.pm' line 525
@ = SQL::Abstract::where(ref(DBIx::Class::SQLMaker), ref(HASH), ref(HA
+SH)) called from file '/usr/share/perl5/SQL/Abstract.pm' line 469
@ = SQL::Abstract::select(ref(DBIx::Class::SQLMaker), ref(ARRAY), 'me.
+id, me.name, me.value, me.modified_at', ref(HASH), ref(HASH)) called 
+from file '/usr/share/perl5/DBIx/Class/SQLMaker.pm' line 172
@ = DBIx::Class::SQLMaker::select(ref(DBIx::Class::SQLMaker), ref(ARRA
+Y), ref(ARRAY), ref(HASH), ref(HASH)) called from file '/usr/share/pe
+rl5/DBIx/Class/Storage/DBI.pm' line 1679
@ = DBIx::Class::Storage::DBI::_gen_sql_bind(ref(DBIx::Class::Storage:
+:DBI::Pg), 'select', ref(ARRAY), ref(ARRAY)) called from file '/usr/s
+hare/perl5/DBIx/Class/Storage/DBI.pm' line 1666
@ = DBIx::Class::Storage::DBI::_prep_for_execute(ref(DBIx::Class::Stor
+age::DBI::Pg), 'select', ref(ARRAY), ref(ARRAY)) called from file '/u
+sr/share/perl5/DBIx/Class/Storage/DBI.pm' line 1810
@ = DBIx::Class::Storage::DBI::_execute(ref(DBIx::Class::Storage::DBI:
+:Pg), 'select', ref(ARRAY), ref(ARRAY), ref(HASH), ref(HASH)) called 
+from file '/usr/share/perl5/DBIx/Class/Storage/DBI.pm' line 2409
@ = DBIx::Class::Storage::DBI::_select(ref(DBIx::Class::Storage::DBI::
+Pg), ref(ARRAY), ref(ARRAY), ref(HASH), ref(HASH)) called from file '
+/usr/share/perl5/DBIx/Class/Storage/DBI.pm' line 2586
@ = DBIx::Class::Storage::DBI::select_single(ref(DBIx::Class::Storage:
+:DBI::Pg), ref(ARRAY), ref(ARRAY), ref(HASH), ref(HASH)) called from 
+file '/usr/share/perl5/DBIx/Class/ResultSet.pm' line 1104
[download]

This puts us at the following function and line of the crash: https://github.com/dbsrgits/sql-abstract/blob/2972827e573b0217735b901088e69c994ba8d226/lib/SQL/Abstract.pm#L1493

sub _join_sql_clauses {
  my ($self, $logic, $clauses_aref, $bind_aref) = @_;

  if (@$clauses_aref > 1) {
    my $join  = " " . $self->_sqlcase($logic) . " ";
    my $sql = '( ' . join($join, @$clauses_aref) . ' )';
    return ($sql, @$bind_aref);
  }
  elsif (@$clauses_aref) {
    ##### CRASH TRIGGERED ON LINE 1493 BELOW #####
    return ($clauses_aref->[0], @$bind_aref); # no parentheses
  }
  else {
    return (); # if no SQL, ignore @$bind_aref
  }
}
[download]

However, trying to add a breakpoint to stack_grow() fails. From further research this is an internal symbol, so does not have a subroutine to match.

My questions are:

• How does stack_grow get called when returning an array like in the above _join_sql_clauses?
• Is there a way to include internal symbol calls (stack_grow) in the Perl debugger? If not, how would you go about tracking that call?
• Does this indicate a memory corruption? If so, are there any Perl tools to help debug such an issue?

Versions: Perl version: 5.32.1 DBIx::Class version: 0.082841 SQL::Abstract version: 1.87

I appreciate any and all feedback, thank you all in advance. - Casey

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.