[completion] GDB completion bug

[Arusekk <arek_koz@o2.pl>]

Hello!

This is my first time with zsh development, so I hope I will not miss 
anything. I am using zsh 5.8 shipped with Gentoo, no patches.
I use oh-my-zsh with plugins=(tig gitfast colored-man-pages colorize 
command-not-found cp dirhistory autojump sudo fast-syntax-highlighting 
zsh-autosuggestions)
and ZSH_THEME="powerlevel10k/powerlevel10k" and no further 
customisations, but I hope this is irrelevant, just activates the 
completion functions.

The bug is not critical in any way, but just happens in the following 
setting:

zsh-5.8% gdb (cursor here) -h

Then it is enough to hit Tab. The -h can be any other option, or even a 
file name, not really important, but there has to be space before 
cursor, and after it (I guess so).

This is the error message:

_pids:shift:13: shift count must be <= $#
_pids:compadd:42: bad option: -m

I traced it down to most probably 
/usr/share/zsh/5.8/functions/Completion/Unix/_gdb calling _pids, but I 
do not know enough of zsh completion to investigate more.

Glad to have found a bug in such reliable software!
Arusekk