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Fix export import conflicts for llvm #147600

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Fix export import conflicts for llvm #147600

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4 changes: 3 additions & 1 deletion compiler/rustc_codegen_llvm/src/callee.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,9 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t

let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());

let llfn = if let Some(llfn) = cx.get_declared_value(sym) {
let llfn = if let Some(llfn) = cx.get_declared_value(sym)
&& (!cx.tcx.is_codegened_item(instance.def_id()) || !instance.def_id().is_local())
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This will break things badly. With this change every time you refer to a different raw-dylib import of the same function, LLVM will use a different name for the function in the object file. For example open, open.1, open.2, ... Only the first reference will actually be resolved by the import library. Also in the case of #113050 where someone defines a local function with the same name, if this function is declared first, then the raw-dylib import get the mangled name and if it is declared second, then if another codegen unit tries to call this function it will call the raw-dylib instead.

The only fix for #113050 I can think of is to have rustc mangle raw-dylib imports and also record this mangled name in the import library rustc generates. The issue with that however is that when a user does want to override a raw-dylib import, they can't do that anymore either.

{
llfn
} else {
let instance_def_id = instance.def_id();
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