sysinfo.pl: unitialized values and division by 0

[clorteau]

Script / WeeChat

• Name of script: sysinfo.pl
• Script version: 1.2.1
• WeeChat version: 4.7.1

This bug has been reported to the script author? Yes

Bug summary

Each time it runs these errors occur:

08:46:09" perl: warning: Use of uninitialized value $vard in subtraction (-) at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 847.
08:46:09" perl: warning: Use of uninitialized value $vara in subtraction (-) at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 847.
08:46:09" perl: warning: Use of uninitialized value $varb in subtraction (-) at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 847.
08:46:09" perl: warning: Use of uninitialized value $varc in subtraction (-) at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 847.
08:46:09" perl: warning: Use of uninitialized value $vara in subtraction (-) at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 871.
08:46:09" perl: error: Illegal division by zero at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 871.
08:46:09" =!= perl: error: Illegal division by zero at /home/northernlights/.local/share/weechat/perl/sysinfo.pl line 871.
08:46:09" =!= perl: error in function "cmd_sysinfo"

Steps to reproduce

1.  Install script
2.  Type /sysinfo
3.  Check the core buffer for the errors

Current behavior

Errors

Expected behavior

No errors :)

[AnonShell]

Took a quick look at this - classic case of missing input validation on /proc/meminfo parsing.

The issue is twofold:

1. meminfo() returns an empty string when a field doesn't exist, but the caller multiplies it by 1024 anyway - hence the uninitialized value warnings
2. Line 871 divides by ($vara - $vard) without checking if that equals zero first

This probably happens on containers or minimal installs where Buffers: or Cached: aren't present in /proc/meminfo. Seen this pattern break on Docker, WSL, and various ARM boards over the years.

Quick fix - just add this guard before line 871:

return "N/A" if (!$vara || ($vara - $vard) == 0);

Or if you want to be more thorough, update meminfo() to return 0 instead of "":

sub meminfo {
    my $string = shift;
    @arr = grep(/^$string/, @meminfo);
    return 0 if (!@arr || !defined $arr[0] || $arr[0] eq "");
    $var = join("\n", $arr[0]);
    @arr = split(/\s+/, $var);
    $var = $arr[1];
    return (defined $var && $var ne "") ? $var : 0;
}

If that helped you and fixed the issue, please submit a PR with the fix, it could help other people as well!