Annotations for symbol visibility (such as `__declspec(dllexport)` and
`__attribute__((visibility("default")))`) is the primary use case.
Such annotations are expected to be needed on declarations (headers)
only, however forcing the annotations into the header file only
is causes missing symbols. Therefore the fix is to force the
annotations into both declaration (header files) and definition
(source files).
I guess MSVC finds this important enough to emit warnings about.
cxxbridge\sources\tests\ffi\lib.rs.cc(1220): warning C4624: 'tests::R': destructor was implicitly defined as deleted
cxxbridge\sources\tests\ffi\lib.rs.cc(1335): warning C4190: 'tests$cxxbridge1$c_return_str' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Str' which is incompatible with C
cxxbridge\include\rust/cxx.h(93): note: see declaration of 'rust::cxxbridge1::Str'
cxxbridge\sources\tests\ffi\lib.rs.cc(1340): warning C4190: 'tests$cxxbridge1$c_return_slice_char' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Slice<const char>' which is incompatible with C
cxxbridge\crate\tests/ffi/tests.h(93): note: see declaration of 'rust::cxxbridge1::Slice<const char>'
cxxbridge\sources\tests\ffi\lib.rs.cc(1345): warning C4190: 'tests$cxxbridge1$c_return_mutsliceu8' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Slice<uint8_t>' which is incompatible with C
cxxbridge\crate\tests/ffi/tests.h(94): note: see declaration of 'rust::cxxbridge1::Slice<uint8_t>'
cxxbridge\sources\tests\ffi\lib.rs.cc(1976): warning C4190: 'tests$cxxbridge1$r_return_str' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Str' which is incompatible with C
cxxbridge\include\rust/cxx.h(93): note: see declaration of 'rust::cxxbridge1::Str'
cxxbridge\sources\tests\ffi\lib.rs.cc(1978): warning C4190: 'tests$cxxbridge1$r_return_sliceu8' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Slice<const uint8_t>' which is incompatible with C
cxxbridge\crate\tests/ffi/tests.h(163): note: see declaration of 'rust::cxxbridge1::Slice<const uint8_t>'
cxxbridge\sources\tests\ffi\lib.rs.cc(1980): warning C4190: 'tests$cxxbridge1$r_return_mutsliceu8' has C-linkage specified, but returns UDT 'rust::cxxbridge1::Slice<uint8_t>' which is incompatible with C
cxxbridge\crate\tests/ffi/tests.h(94): note: see declaration of 'rust::cxxbridge1::Slice<uint8_t>'
Fix for warning when running cargo test.
```
warning: /Users/pickett/Documents/GitHub/cxx/target/debug/build/cxx-test-suite-de711daed7f2e46d/out/cxxbridge/sources/tests/ffi/lib.rs.cc:1256:10: warning: struct template 'Slice' was previously declared as a class template; this is valid, but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
warning: template struct ::rust::Slice<const char>;
warning: ^
warning: /Users/pickett/Documents/GitHub/cxx/target/debug/build/cxx-test-suite-de711daed7f2e46d/out/cxxbridge/include/rust/cxx.h:146:7: note: previous use is here
warning: class Slice final
warning: ^
warning: /Users/pickett/Documents/GitHub/cxx/target/debug/build/cxx-test-suite-de711daed7f2e46d/out/cxxbridge/sources/tests/ffi/lib.rs.cc:1256:10: note: did you mean class here?
warning: template struct ::rust::Slice<const char>;
warning: ^~~~~~
warning: class
```
MSVC fails to compile code like the following unless there is an
explicit instantiation of the class template:
template <typename T>
class slice {};
//template class slice<int>;
extern "C" slice<int> repro() { return {}; }
Error:
<source>(6): error C2526: 'repro': C linkage function cannot return C++ class 'slice<int>'
<source>(6): note: see declaration of 'slice<int>'
<source>(6): error C2562: 'repro': 'void' function returning a value
<source>(6): note: see declaration of 'repro'
Compiler returned: 2
This results in slightly less noise when code generation produces an
error during a Cargo build.
Before:
process didn't exit successfully: `/git/example-cxx/target/debug/build/example-f20ef12178a95a23/build-script-build` (exit code: 1)
--- stdout
cargo:CXXBRIDGE_PREFIX=example
cargo:CXXBRIDGE_DIR0=/git/example-cxx/target/debug/build/example-188c8410ffc8bb7d/out/cxxbridge/include
cargo:CXXBRIDGE_DIR1=/git/example-cxx/target/debug/build/example-188c8410ffc8bb7d/out/cxxbridge/crate
--- stderr
error[cxxbridge]: extern type with lifetimes is not supported yet
┌─ src/main.rs:9:21
│
9 │ type Object<'a>;
│ ^^ extern type with lifetimes is not supported yet
After:
process didn't exit successfully: `/git/example-cxx/target/debug/build/example-f20ef12178a95a23/build-script-build` (exit code: 1)
--- stderr
error[cxxbridge]: extern type with lifetimes is not supported yet
┌─ src/main.rs:9:21
│
9 │ type Object<'a>;
│ ^^ extern type with lifetimes is not supported yet
