From 88d8fd2742cad79f92b73eabb2559e8b26bb021e Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Mon, 7 Apr 2025 12:35:02 -0700 Subject: [PATCH] Ignore zero-sized types in wasm future-compat warning This commit fixes a false positive of the warning triggered for #138762 and the fix is to codify that zero-sized types are "safe" in both the old and new ABIs. --- compiler/rustc_monomorphize/src/mono_checks/abi_check.rs | 5 +++++ tests/ui/lint/wasm_c_abi_transition.rs | 6 ++++++ 2 files changed, 11 insertions(+) diff --git a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs index 0f5bdc8d768..aa4f0fee1ad 100644 --- a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs +++ b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs @@ -111,6 +111,11 @@ fn wasm_abi_safe<'tcx>(tcx: TyCtxt<'tcx>, arg: &ArgAbi<'tcx, Ty<'tcx>>) -> bool } } + // Zero-sized types are dropped in both ABIs, so they're safe + if arg.layout.size.bytes() == 0 { + return true; + } + false } diff --git a/tests/ui/lint/wasm_c_abi_transition.rs b/tests/ui/lint/wasm_c_abi_transition.rs index 1fe81679e65..6a933a0de03 100644 --- a/tests/ui/lint/wasm_c_abi_transition.rs +++ b/tests/ui/lint/wasm_c_abi_transition.rs @@ -39,3 +39,9 @@ pub fn call_other_fun(x: MyType) { unsafe { other_fun(x) } //~ERROR: wasm ABI transition //~^WARN: previously accepted } + +// Zero-sized types are safe in both ABIs +#[repr(C)] +pub struct MyZstType; +#[allow(improper_ctypes_definitions)] +pub extern "C" fn zst_safe(_x: (), _y: MyZstType) {}