pub static UNSUPPORTED_CALLING_CONVENTIONS: &Lint
Expand description
The unsupported_calling_conventions
lint is output whenever there is a use of the
stdcall
, fastcall
, thiscall
, vectorcall
calling conventions (or their unwind
variants) on targets that cannot meaningfully be supported for the requested target.
For example stdcall
does not make much sense for a x86_64 or, more apparently, powerpc
code, because this calling convention was never specified for those targets.
Historically MSVC toolchains have fallen back to the regular C calling convention for targets other than x86, but Rust doesn’t really see a similar need to introduce a similar hack across many more targets.
§Example
extern "stdcall" fn stdcall() {}
This will produce:
warning: use of calling convention not supported on this target
--> $DIR/unsupported.rs:39:1
|
LL | extern "stdcall" fn stdcall() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(unsupported_calling_conventions)]` on by default
= warning: this was previously accepted by the compiler but is being phased out;
it will become a hard error in a future release!
= note: for more information, see issue ...
§Explanation
On most of the targets the behaviour of stdcall
and similar calling conventions is not
defined at all, but was previously accepted due to a bug in the implementation of the
compiler.