Are GCC and Clang parsers really handwritten?

Question

It seems that GCC and LLVM-Clang are using handwritten recursive descent parsers, and not machine generated, Bison-Flex based, bottom up pa

Answer 1

gcc's parser is handwritten.. I suspect the same for clang. This is probably for a few reasons:

• Performance: something that you've hand-optimized for your particular task will almost always perform better than a general solution. Abstraction usually has a performance hit
• Timing: at least in the case of GCC, GCC predates a lot of free developer tools (came out in 1987). There was no free version of yacc, etc. at the time, which I'd imagine would've been a priority to the people at the FSF.

This is probably not a case of "not invented here" syndrome, but more along the lines of "there was nothing optimized specifically for what we needed, so we wrote our own".