Reading config file fails with latest GCC in Debian

Debian's test infrastructure discovered that osk-sdl built with GCC 12 fails to read it's config file. Specifically, the test output is:

 autopkgtest [05:11:09]: test test-functional: [-----------------------
 ** Testing key script with 'physical' key input
 INFO: osk-sdl v0.66
 ERROR: Syntax error on line 4
 ERROR: Could not parse config file: ./osk.conf
 ERROR: No valid config file specified, use -c [path]
 ERROR: Unexpected result!
 	got:            
 	expected:       postmarketOS
 ** Testing osk toggle button and 'mouse' key input
 INFO: osk-sdl v0.66
 ERROR: Syntax error on line 4
 ERROR: Could not parse config file: ./osk.conf
 ERROR: No valid config file specified, use -c [path]
 ERROR: Unexpected result!
 	got:            
 	expected:       qwerty
 autopkgtest [05:11:25]: test test-functional: -----------------------]
 autopkgtest [05:11:25]: test test-functional:  - - - - - - - - - - results - - - - - - - - - -
 test-functional      FAIL non-zero exit status 2
 autopkgtest [05:11:25]: @@@@@@@@@@@@@@@@@@@@ summary
 test-machine-functional SKIP Test requires machine-level isolation but testbed does not provide that
 test-functional      FAIL non-zero exit status 2

I have narrowed this down to the first check in https://gitlab.postmarketos.org/postmarketos/osk-sdl/-/blob/master/src/config.cpp#L197, which seems to always return false now, even though eq and val are correctly set.

While playing around with it myself, removing just this part of the check allows the config to be loaded successfully, though some keypresses are still missed. This may be an issue with the test or some other bug.

The failing config file is mostly default.

# Config file for osk-sdl
# The space around the = is important

wallpaper = #000000

keyboard-background = #0E0E12
keyboard-map = us
keyboard-font = /usr/share/fonts/truetype/dejavu/DejaVuSans.ttf
keyboard-font-size = 24

key-foreground = #FFFFFF
key-foreground-highlighted = #0E0E12
key-background-letter = #5A606A
key-background-return = #003C00
key-background-other = #32363E
key-background-highlighted = #FFFFFF
key-radius = 0
key-vibrate-duration = 100
key-preview-popup = true

inputbox-foreground = #FFFFFF
inputbox-foreground-error = #7E141A
inputbox-background = #32363E
inputbox-background-error = #E76A63
inputbox-radius = 0

animations = true