fix: handle zero-sized memory intrinsics#876
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mizoz wants to merge 2 commits intorust-lang:masterfrom
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bjorn3
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Apr 28, 2026
| return Ok(()); | ||
| } | ||
| return Err(Instance::new_raw(instance.def_id(), instance.args)); | ||
| } |
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Why not change the memset, memcpy and memmove methods on Builder? Also this only helps with ZST types, not with copying zero elements.
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You're right — this should cover the generic I had avoided changing the builder methods because a first pass that split the current block inside those methods caused later MIR emission to keep writing to the terminated block in local testing. I'm going to rework this instead of trying to paper over it, so the updated patch handles runtime zero sizes cleanly as well. |
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Fixes #516.
This avoids lowering zero-sized
copy,copy_nonoverlapping, andwrite_bytesintrinsics to GCC memory builtins. For zero-sized element types, the operation has no bytes to touch, so the backend can return before the fallback lowering emitsmemcpy,memmove, ormemset.A small run test covers the three zero-sized memory intrinsic paths using
()pointers.Tested with:
git diff --checkcargo fmt --check./y.sh test --mini-testscargo test -p rustc_codegen_gcc --test lang_tests zero_sized_mem -- --nocapture