system, orig: 0.22s
system, paolo: 0.22s
system, ".": 0.15s
compat, orig: 150.88s
compat, paolo: 0.43s
compat, ".": 0.15s
Besides the exponential behavior on the original regex, it is still
about twice as slow as the system one.
The reason is that the glibc regex is a DFA-based matcher. It is much
slower on regexes with backreferences, but otherwise it is faster.
1. Replace the builtin diff.java.xfuncname pattern with what Paolo
suggested (though I haven't verified its correctness beyond a
cursory look at the results).
I checked it a bit harder, but still it is not easy to check because of
the false positives in the original regex. I'm pretty sure it's correct
though; I find it even easier to read (though longer) than the
original one.
I haven't looked at how large or how portable the glibc
implementation is.
Decently portable, but I don't think it's worth it. Users that write
regexes so complex should know of the exponential behavior, I think.
Paolo
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