PROMETHIA (May 22 2023 at 12:57): PROMETHIA (May 22 2023 at 12:57):I've noticed that it seems like cranelift is unable to produce or call C ABI functions. Are there any plans to be able to do so or am I missing something obvious?
I've also noticed that lots of examples, especially JIT ones, seem to use C ABI in rust to communicate with the jitted functions which are usually platform default ABI, such as fastcall/systemV. Given that rust can choose every ABI that cranelift supports, including the default system ABI, shouldn't these examples all use something like SystemV instead?
bjorn3 (May 22 2023 at 14:30):extern "C" in rust is the platform default ABI, so SystemV on Unix and WindowsFastcall on Windows.
bjorn3 (May 22 2023 at 14:30):Which examples are you referring to specifically?
PROMETHIA (May 22 2023 at 14:39):For example, https://github.com/bytecodealliance/wasmtime/blob/main/cranelift/jit/examples/jit-minimal.rs transmutes the function pointer to an extern "C" pointer and then calls it, but it's declared (implicitly) with e.g. fastcall on windows.
And I thought extern "system" in rust was platform default, extern "C" is C ABI?
bjorn3 (May 22 2023 at 14:45):make_signature() uses the C abi by default.
bjorn3 (May 22 2023 at 14:47):On 32bit x86 Windows there is a difference between extern "system" which is used for system libraries and extern "C" which is used for the rest. On every other system there is no difference. I have been referring to extern "C" as platform default.
PROMETHIA (May 22 2023 at 14:52):Ah, I see. I thought C ABI was referring to a concrete ABI such as cdecl, not referring to "whatever the system C compiler uses". That makes more sense. Thank you!
Last updated: Nov 22 2024 at 17:03 UTC