Ensure bridging header function prototypes are valid #1512
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Actually, that's inaccurate: it's a hybrid swift + objc project and i think the prototype error was coming from building a |
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Any chance you can demonstrate the problem in one of our fixtures? |
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Yes. I'm trying to figure that out now, there don't seem to be any existing fixtures which demonstrate running a C/obj-c compiler over the FFI.h. |
Compiling my swift project I am seeing:
```
Generated/mycrateFFI.h:75:45: error: this function declaration is not a prototype [-Werror,-Wstrict-prototypes]
```
for the `ffi_mycrate_uniffi_contract_version` and
`uniffi_mycrate_checksum_func_myfun` declarations.
This is because they take no arguments which is emitted as `()`, for C `(void)`
is required, C++ is happy with either.
The included fixture attempts to validate that the generated header is valid
according to a compiler at a highly pendantic level, interestingly this doesn't
actually cover `-Wstrict-prototypes` so that is enabled separately.
Add a specific case to `swift::arg_list_ffi_decl` to handle this by adding the
`void` when there are no arguments. The resulting diff is:
```diff
--- swift_bridging_header_compileFFI.h.old 2023-04-06 14:30:29.994435300 +0000
+++ swift_bridging_header_compileFFI.h.new 2023-04-06 14:31:14.047300820 +0000
@@ -54,6 +54,7 @@
void uniffi_swift_bridging_header_compile_fn_func_no_arguments(
RustCallStatus *_Nonnull out_status
+
);
RustBuffer ffi_swift_bridging_header_compile_rustbuffer_alloc(
@@ -73,9 +74,11 @@
);
uint32_t ffi_swift_bridging_header_compile_uniffi_contract_version(
+ void
);
uint16_t uniffi_swift_bridging_header_compile_checksum_func_no_arguments(
+ void
);
```
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Done. |
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Wow, C is so weird. This seems correct to me based on https://en.wikipedia.org/wiki/Compatibility_of_C_and_C%2B%2B.
Yes. I can confirm |
Compiling my swift project I am seeing:
for the
ffi_mycrate_uniffi_contract_versionanduniffi_mycrate_checksum_func_myfundeclarations.This is because they take no arguments which is emitted as
(), for C(void)is required, C++ is happy with either.Add a specific case to
swift::arg_list_ffi_declto handle this. The resulting diff is: