[PATCH] D155955: [Clang] Improve the handling of large arrays evaluation.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added a comment.

> Note sure what you mean. Making sure we use size_t for all array extents is not something that can be fixed overnight but more importantly, it does not help: Would it not overflow, the allocation would still fail.

Oh, right, it would be sizeof(APValue) * UINT_MAX, which would break in any practical usage.

> I don't think that would make sense in actual code, and having some sort of sparse array is something I considered. And we already delay allocation in some cases, but we do need to create elements to destroy them, read them, etc. So while it may be possible, it seems... complicated.

Definitely not simple, sure.

> I think a more viable long term fix might be to not crash on allocation failure, and/or to have a way to limit the allocation to some portion of the available memory.

Making the compiler's behavior depend on the amount of memory installed in the user's computer seems like a non-starter.  I think we just have to stick with some combination of:

- Try to reduce excessive memory usage in constant folding.
- Add strict limits memory usage limits for optional constant folding
- Maybe consider disobeying the standard slightly in certain cases: the standard requires that we constant-fold the initializers for all global variables, but that might not really be viable for globals that are expensive to evaluate.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D155955/new/

https://reviews.llvm.org/D155955