Error while running Makefile in Ubuntu

[AverageAssemblyProgrammer]

When I try to run the Makefile the output says "g++: error: unrecognized command line option ‘-std=c++20’; did you mean ‘-std=c++2a’?" then if I change -std=c++20 to -std=c++2a in the Makefile, it gives me more errors, they are:-

1. "error: ‘constinit’ does not name a type 3 | extern const constinit std::array<unsigned,256> xterm256table;"

2. "error: ‘xterm256table’ was not declared in this scope 366 | case m(MODE38_5): color = 0; a = xterm256table[a & 0xFF];"

3. "error: ‘xterm256table’ was not declared in this scope 622 | case 4: {unsigned v = xterm256table[p[1]&0xFF];"

what should I do to fix these errors?

my distribution is Ubuntu 20.04.4 LTS x86_64 kernel is 5.13.0-41-generic.

[bisqwit]

Too old compiler version is being used.

[AverageAssemblyProgrammer]

soo what do I do about it? do I update the compiler?

my gcc version is 9.4.0 my g++ version is 9.4.0