use API lock in helper function ccalls

[lxvm]

Hi,

This pr wraps ccalls in src/api/helpers.jl with the library API lock. I believe the handling of strings is still thread-safe, but it would help for someone to check. Also, if this pr should be implemented at the level of the generator I may need some assistance with where to start.

Fixes #1179

[mkitti]

Thank you. This is probably the right direction. Does applying this lock solve the issue in #1179 for you? Could we also implement a minimal version of the MWE you reported in #1179 as a test?

[lxvm]

I checked that this pr fixes the issue in #1179 on my computer. To turn that MWE into a test, would I have to add a new test suite in a multi-threaded Julia process? I don't see other multi-threaded tests so I'm not sure what the best way to write such a test would be.

For the formatter, I'll try and fix the failing test soon.

[mkitti]

For the formatter you can run contrib/format/format.jl and push enter until it says it was formatted.

[mkitti]

For a multiple thread test, you can launch another Julia process as follows.

run(`$(Base.julia_cmd()) -t 2 -E "Threads.nthreads()"`)

Instead of -E you could just provide a file to run.

[lxvm]

Thanks for the recommendations. I added a test similar to what you described. I think it uses Pkg.jl internals to get a path to the test environment, which may be undesirable, but the test does show the MWE gets fixed by this pr when run on my machine. CI shows it passes on all platforms and versions except for nightly, but I'm not sure why this fix would segfault on nightly.

[mkitti]

Close enough for me. I'll merge and investigate the failures further or mark them as broken.