alexanderkyte added a comment.
This change is causing mono's native interop with C code compiled from clang to
break. After some investigation, we're tracked bitcode differences between
tests that fail versus not. When we upgrade the compiler to Xcode 8.3, we see
that code generated to call functions returning empty structs will now generate
code that crashes.
This seems to be us trying to pass arguments assuming that clang exhibits the
same behavior it used to. It is easy enough for us to generate code for what
clang does now, but that code would break if forced to interact with C compiled
by gcc and older clangs.
Is there a way for callers of clang-emitted code to detect which ABI clang is
going to use when returning an empty struct? This ABI change does not seem to
admit backwards compatibility.
xcode73's clang -emit-llvm generates:
- define void @ret(%struct.AStruct* noalias sret %agg.result, i32 %a) #0 {
while xcode83's clang generates:
- define void @ret(i32) #0 {
Repository:
rL LLVM
https://reviews.llvm.org/D16808
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