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Wrangling Untrusted File Formats Safely
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convert wuffs asserts into back-end asserts #77

Open ratchetfreak opened 2 years ago

ratchetfreak commented 2 years ago

Can there be an option to convert wuffs-side asserts into asserts in the generated code?

This could be a macro which lets the user code pick which behavior to have for them.

So the assert can translate into nothing (like it is now), or a full error like if not cond {return "#internal error: failed assert";}, or an actual assert(cond);, or even an assume(cond);.

Theoretically the compiler should be able to optimize out all these checks but there will be cases where it cannot make the assumptions necessary like across a yield. This in turn could help the optimizer figure out better options based on the invariants that are present in wuffs but not present in the backend.

nigeltao commented 2 years ago

Do you have an actual example (with benchmark numbers) where this helps the compiler / optimizer or is it hypothetical at this stage?

If we do do this, one subtlety is that Wuffs-side asserts work in ideal numbers but compilers work in fixed-sized integers. assert (x + 1) > x is valid for mathematical integers but isn't always true for uint32_t integers (and for signed fixed-size integers, this might even be "undefined behavior").

ratchetfreak commented 2 years ago

It's hypothetical at this stage.

and yeah that does complicate matters