Rustine: mimalloc C → Rust Translation

[enum-class]

This PR presents an initial version of Rust translation of Microsoft's mimalloc (dev3 branch) using Rustine, an LLM-powered C-to-Rust whole-repository translation/validation/debugging pipeline. It is worth noting that C2Rust fails to translate mimalloc because it struggles with complex atomic operations and strict thread-safety requirements. In contrast, Rustine succeeds by focusing on semantic intent rather than relying on shallow, syntax-level transpilation.

The translation of the entire repository (including application and test code) is 100% compilable. Test translation quality is manually checked, and execution of translated tests on translated code results in 100% test pass (test_api, test_api_fill, test_stress).

Please review the translations and let us know if you are interested in additional stats related to Rust code (safety features, raw pointer usage, including pointer arithmetics, clippy results, and code quality metrics). We would be happy to incorporate your feedback into the pipeline and improve the translation.

[enum-class]

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[enum-class]

@enum-class please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@microsoft-github-policy-service agree [company="{your company}"]

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• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

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[Zoxc]

The LLM output looks quite bad, presumedly since it tries to stay close to C without using idiomatic Rust. The use of references I've seen looks highly questionable also. Compare it to https://github.com/Zoxc/fjall for a more proper Rust port.

[jcotton42]

It only took me until here to find a blatantly incorrect translation

mimalloc/src/alloc.c

Lines 270 to 282 in b196396

	void* mi_expand(void* p, size_t newsize) mi_attr_noexcept {
	#if MI_PADDING
	// we do not shrink/expand with padding enabled
	MI_UNUSED(p); MI_UNUSED(newsize);
	return NULL;
	#else
	if (p == NULL) return NULL;
	const mi_page_t* const page = mi_validate_ptr_page(p,"mi_expand");
	const size_t size = _mi_usable_size(p,page);
	if (newsize > size) return NULL;
	return p; // it fits
	#endif
	}