I wrote a parser-generator in C and it took less than 42 days. Your mileage may vary.

https://github.com/gregtour/parsergenerator

Most of the C code is less than 1.5k LOC for the functional part, and this minimal, self-compiling C compiler has a parser that is nearly 3,000 lines long.

Even if it took 1,000 lines of extra code for the non-LR aspects of C's grammar, I think it would be the same amount of work.

This just leaves you in a better position to write a C++, Go, or Java compiler at the end.