grep and git grep not working on a Gentoo system

[o0nd7ots]

Hello,

I have grep compiled with PCRE support on my host.
I also have git grep but do not know how to check the pcre support.

TODOs section does not show up unless I install rpgrep.

Is there a way I can debug this?
Here's how Emacs describes the variable:

magit-todos-scanner is a variable defined in ‘magit-todos.el’.

Its value is ‘magit-todos--scan-with-git-diff’
Original value was nil

File scanning method.
"Automatic" will attempt to use rg, ag, git-grep, and
find-grep, in that order.

  You can customize this variable.

[alphapapa]

Hello,

rg is the best, fastest scanner to use, anyway. Why don't you want to use it?

Since it works for you, I don't think it would be a good use of time trying to debug the other scanners on an unspecified platform. I'd recommend just using what works.

[o0nd7ots]

Why don't you want to use it?

I already have two implementations installed. I want to use them and see if they are enough for me as I try to avoid installing many packages.

That is why I care about it and want to make it work with the two greps that I have installed.
I am running Gentoo and GNU Emacs 29.4.
What other details could be helpful?

[alphapapa]

I'm afraid I don't have the time to offer support for making secondary and tertiary scanners work when the primary one is working for you. In this day and age, disk space is not at a premium, and ripgrep is not a large utility, so there's no practical reason to not just install and use it. If you refuse to use it, you will have to debug the issues with the other scanners on your own. FWIW, they are known to work, so if they don't on your Gentoo system, I'd guess that you might be using non-standard build flags which are making them incompatible. (Long gone are the days when it was worth the time and trouble to use system-specific build flags on a Gentoo system to eke out a few percentage points of performance improvements. We're talking about microseconds of theoretical benefit here.)