Try to repro memory out of bounds errors in CI #1198
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Adds custom PHP memory storage handlers to stop PHP from attempting to partial unmap memory via the `munmap()` function. Emscripten allocators do not support using `munmap()` to partially unmap memory. They fail for partial unmaps, and when attempts fail, memory is leaked because PHP thinks the memory is free while Emscripten libs consider it allocated. The custom memory storage handlers take over responsibility for allocating and freeing aligned memory chunks. The handlers use `posix_memalign()` and `free()` instead of `mmap()` and `munmap()`, and this appears to resolve the problem. The handlers are added as part of a PHP extension, which is not perfect because allocation can happen before the extension is initialized. But the amount of allocation before the workaround is applied should be quite small. ## Testing Instructions Before applying this patch: Run [this test script](https://gist.github.com/brandonpayton/934d96d76b96557e94ad6983aaffa09f) and verify that it OOMs. After applying this patch: Rerun the test script and verify that it completes after 1000 interations. ## Remaining work - [x] Compare performance with php-wasm builds prior to this patch and reconsider if 20% slower. - [x] Find out whether it is sufficient to add the workaround during the PHP module init phase rather than during each request init - [x] Address minor TODO comments in wasm_memory_storage.c - [x] See if we can run the test script as part of tests under `packages/php-wasm/node/src/test`
brandonpayton
added
[Type] Bug
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Hmm... I think testing CI may require a branch in this repo. Creating a duplicate PR to test that theory... |
It looks like that is the case. Closing this PR which is based on a branch in my personal fork. |
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This is a test PR to hopefully reproduce memory access out of bounds errors with #1189.
So far, @adamziel has only encountered errors in CI (see #1194), but there was one error report in WP.org Slack:
https://wordpress.slack.com/archives/C06Q5DCKZ3L/p1712232849960669