How to build to debug with gdb?

[Giuseppe Crino']

Hello, to debug some issues I built and installed git via

$ make prefix=/usr/local DEVELOPER=1 CFLAGS="-O0 -g"
$ sudo make install
$ git --version # git version 2.23.0.40.g4d8aada92f 

But it seems there's still some optimization going on that prevents gdb from 
working correctly.

For example

(gdb) b builtin/config.c:752
Breakpoint 1 at 0x43942: file builtin/config.c, line 752.
(gdb) r config --global --edit
Starting program: /usr/local/bin/git config --global --edit
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libth
read_db.so.1".

Breakpoint 1, cmd_config (argc=0, argv=<optimized out>,
    prefix=<optimized out>) at builtin/config.c:753
    753                             if (fd >= 0) {
    (gdb) p fd
    $1 = <optimized out>

 What am I missing?

 -Giuseppe