[ruby-core:106882] [Ruby master Bug#18446] LSAN reporting

Issue #18446 has been updated by ibylich (Ilya Bylich).


Thanks, I've seen this gem before. Unfortunately, Valgrind doesn't work on the latest MacOS (starting from Catalina? I don't remember), there are a few forks, but they were buggy and I couldn't find any that works on the current latest MacOS, so LSAN is the only thing I can use locally.

Also, as I understand, it uses suppression files. I had the same idea with LSAN - https://github.com/lib-ruby-parser/ruby-bindings/blob/master/LSan.supp, but every time I added a new filter I wasn't sure if I'm doing the right thing. Would be great if it could be fixed directly in Ruby.

----------------------------------------
Bug #18446: LSAN reporting
https://bugs.ruby-lang.org/issues/18446#change-95690

* Author: ibylich (Ilya Bylich)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0dev (2021-12-27T13:57:46Z master be476f38f9) [x86_64-darwin20]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
ASAN ships with LSAN (LeakSANinitizer) that (if compiled with ASAN) can be enabled by adding `ASAN_OPTIONS=detect_leaks=1` env variable. As I know it can also be injected dynamically via `LD_PRELOAD`/`DYLD_INSERT_LIBRARIES` on Linux/Mac. Currently it reports a bunch of memory leaks of different sizes:

```
...
1 kilometer of leaks
...

SUMMARY: AddressSanitizer: 540806 byte(s) leaked in 11450 allocation(s).
```

First of all, are these leaks real? valgrind also reports them. If they are not real, is there a way to make LSAN ignore them? As I know MRI uses ASAN programmatically in many place (like in `gc.h`) to poison (i.e. "mark"?) some memory areas, and so my hunch is that these leaks are false-positive.

Then, is it possible to "fix" reporting? I'm asking because it'd be very useful for native extensions development, ASAN+LSAN is a good combo to find and unroll segfaults and memory leaks, but LSAN is barely usable right now.



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