The described compiler bug is reproducible on gentoo [0] (gcc-10.2.0-r5, that is patchlevel 6).
So it is not a debian - specific bug
[0] https://github.com/Return-To-The-Roots/s25client/issues/1327#issuecomment-755180727
- Bug#979350: gcc-10: compiling bug of code for https://github.... Jens Ungerer
- Bug#979350: Confirmation of G++/GCC bug on gentoo Jens Ungerer
- Bug#979350: Minimal Example Jens Ungerer
- Bug#979350: Minimal Example: Command and Output Jens Ungerer
