On 30.01.23 21:08, Junio C Hamano wrote: > Junio C Hamano <gitster@xxxxxxxxx> writes: > >> If we were to keep that "die", it is absolutely required, I would >> think. Users who got their Git with JIT-enabled pcre2 may be >> viewing JIT merely as "a clever optimization the implementation is >> allowed to use when able", without knowing and more importantly >> without wanting to know how to disable it from within their >> patterns. >> >> But can't we drop that die() if we took the v1 route? > > Having said all that, I do not mind queuing v2 if the "use *NO_JIT > to disable" is added to the message to help users who are forced to > redo the query. > > And in practice, it shouldn't make that much difference, because the > only scenario (other than the SELinux-like situation where JIT is > compiled in but does not work at all) that the difference may matter > would happen when a non-trivial portion of the patterns users use > are not workable with JIT, but if that were the case, we would have > written JIT off as not mature enough and not yet usable long time > ago. So, in practice, patterns refused by JIT would be a very tiny > minority to matter in real life, and "failing fast to inconvenience > users" would not be too bad. Exactly! > So while I still think v1's simplicity is the right thing to have > here, I think it is waste of our braincell to compare v1 vs v2. As > v2 gives smaller incremental behaviour change perceived by end > users, if somebody really wanted to, I'd expect that a low-hanging > fruit #leftoverbit on top of such a patch, after the dust settles, > would be to > > (1) rename pcre2_jit_functional() to fall_back_to_interpreter() or > something, > > (2) add a configuration variable to tell fall_back_to_interpreter() > that any form of JIT error is allowed to fall back to > interpreter(). > > and such a patch will essentially give back the simplicity of v1 to > folks who opt into the configuration. Fair enough. But aside from the W|X memory allocation denial exception is the likelihood to run into the limitations of PCRE2's JIT requiring the interpreter fallback so little (as otherwise we'd see it in the past already), I think, the demand for such a knob is basically nonexistent. Thanks, Mathias
