Improve analyzegc experience

[staticfloat]

This makes the analyzegc experience faster, more beautiful, and a lot easier to run from a clean clone, as we expect to do regularly on CI. In particular, the clang analysis pass is now invoked in serial, which reduces runtime from 6.5 minutes to 2.5 minutes on a 4-core box; which isn't a bad speedup.

[staticfloat]

Triggered a new CI run; looks like it's working! :D

Will clang return nonzero if something fails an analysis sweep? If not, it's always going to be green.

[Keno]

Will clang return nonzero if something fails an analysis sweep? If not, it's always going to be green.

I think so, but you can try it out, but just deleting any JL_GC_POP line. The analyzer will catch that.

[staticfloat]

I think so, but you can try it out, but just deleting any JL_GC_POP line. The analyzer will catch that.

Looks like the answer is no, clang does not turn analyzer warnings into errors, even with -Werror. Here's an SO answer about the same thing, with a very mac/iphone specific solution that I don't think will work for us.

We could check to make sure that clang does not output anything, but that seems a little fragile.

[StefanKarpinski]

Wut?! This is UNIX 101. Maybe submit a patch to clang to make it work the right way when running in static analysis mode?

[staticfloat]

@Keno is it possible for us to write a checker plugin that processes the results of all other checkers and turns any exception into something fatal? The only other option that I can think of is to have it output something more structured, such as a .plist, consume that .plist and ensure that it is an empty array.

[Keno]

I looked into this for a bit, but didn't see anything obvious. Enabling the analyzer explicitly disables -Werror and the analyzer is hardcoded to emit its results as a warning. I do feel like we must be missing something stupid, so probably worth emailing the clang list to ask about.

[staticfloat]

I'm going to merge this for now, to get rid of the red X's, and because we will want these changes merged in any case; we'll fix the fault detection in a future PR.

[Keno]

Shall I email cfe-dev or do you want to?

[staticfloat]

Please go ahead; I couldn't even find the source for the analyzer parts of clang.

[Keno]

With https://reviews.llvm.org/D62885, adding -Xanalyzer -analyzer-werror will do what you want