Parsing a single header file in isolation is cheap, but each header will include others, and templates mean many headers contain large amounts of code inline. F

Parsing a single header file in isolation is cheap, but each header will include others, and templates mean many headers contain large amounts of code inline. For instance, just including <vector> results in the compiler having to look at almost 30kloc, on my system: $ clang -x c++ -E - <<<"#include <vector>" | wc -l 27378 Other headers are similar: algorithm 23103 array 23450 memory 15909 random 52107 thread 31424 tuple 9240 (Of course, a bunch of this code is shared, e.g. including both thread and vector is “only” 35713 loc total, not 60kloc.) I believe C++ compilers have SIMD-accelerated lexers/parsers because of the sheer explosion of code due to headers and templates.