openharmony/third_party_rust_cxx
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Pass Str in PtrLen representation

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MSVC is hesitant about passing private fields in an extern "C" signature.
Repro:

    struct Str1 {
      const char *ptr;
      size_t len;
    };

    struct Str2 {
    private:
      const char *ptr;
      size_t len;
    };

    extern "C" {
      Str1 str1();
      Str2 str2();
    }

Warning from MSVC v19.27:

    warning C4190: 'str2' has C-linkage specified, but returns UDT 'Str2' which is incompatible with C
This commit is contained in:
David Tolnay 2020-10-31 19:46:41 -07:00
parent 54742b7ced
commit 0356d33acb
No known key found for this signature in database
GPG Key ID: F9BA143B95FF6D82
3 changed files with 39 additions and 6 deletions
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40
gen/src/write.rs
View File

@ -324,7 +324,7 @@ fn write_include_cxxbridge(out: &mut OutFile, apis: &[Api]) {
out.begin_block("namespace");
if needs_trycatch || needs_rust_error {
if needs_trycatch || needs_rust_error || needs_rust_str && !out.header {
out.begin_block("namespace repr");
writeln!(out, "struct PtrLen final {{");
writeln!(out, " const void *ptr;");
@ -333,7 +333,28 @@ fn write_include_cxxbridge(out: &mut OutFile, apis: &[Api]) {
out.end_block("namespace repr");
}
if needs_rust_str && !out.header {
out.next_section();
writeln!(out, "template <>");
writeln!(out, "class impl<Str> final {{");
writeln!(out, "public:");
writeln!(
out,
" static Str new_unchecked(repr::PtrLen repr) noexcept {{",
);
writeln!(out, " Str str;");
writeln!(out, " str.ptr = static_cast<const char *>(repr.ptr);");
writeln!(out, " str.len = repr.len;");
writeln!(out, " return str;");
writeln!(out, " }}");
writeln!(out, " static repr::PtrLen repr(Str str) noexcept {{");
writeln!(out, " return repr::PtrLen{{str.ptr, str.len}};");
writeln!(out, " }}");
writeln!(out, "}};");
}
if needs_rust_error {
out.next_section();
writeln!(out, "template <>");
writeln!(out, "class impl<Error> final {{");
writeln!(out, "public:");
@ -619,6 +640,7 @@ fn write_cxx_function_shim(out: &mut OutFile, efn: &ExternFn, impl_annotations:
}
match &efn.ret {
Some(Type::Ref(_)) => write!(out, "&"),
Some(Type::Str(_)) if !indirect_return => write!(out, "::rust::impl<::rust::Str>::repr("),
Some(Type::SliceRefU8(_)) if !indirect_return => {
write!(out, "::rust::Slice<uint8_t>::Repr(")
}
@ -638,6 +660,12 @@ fn write_cxx_function_shim(out: &mut OutFile, efn: &ExternFn, impl_annotations:
} else if let Type::UniquePtr(_) = &arg.ty {
write_type(out, &arg.ty);
write!(out, "({})", arg.ident);
} else if let Type::Str(_) = arg.ty {
write!(
out,
"::rust::impl<::rust::Str>::new_unchecked({})",
arg.ident,
);
} else if arg.ty == RustString {
write!(
out,
@ -658,7 +686,7 @@ fn write_cxx_function_shim(out: &mut OutFile, efn: &ExternFn, impl_annotations:
match &efn.ret {
Some(Type::RustBox(_)) => write!(out, ".into_raw()"),
Some(Type::UniquePtr(_)) => write!(out, ".release()"),
Some(Type::SliceRefU8(_)) if !indirect_return => write!(out, ")"),
Some(Type::Str(_)) | Some(Type::SliceRefU8(_)) if !indirect_return => write!(out, ")"),
_ => {}
}
if indirect_return {
@ -850,6 +878,7 @@ fn write_rust_function_shim_impl(
write!(out, "(");
}
Type::Ref(_) => write!(out, "*"),
Type::Str(_) => write!(out, "::rust::impl<::rust::Str>::new_unchecked("),
_ => {}
}
}
@ -865,6 +894,7 @@ fn write_rust_function_shim_impl(
write!(out, ", ");
}
match &arg.ty {
Type::Str(_) => write!(out, "::rust::impl<::rust::Str>::repr("),
Type::SliceRefU8(_) => write!(out, "::rust::Slice<uint8_t>::Repr("),
ty if out.types.needs_indirect_abi(ty) => write!(out, "&"),
_ => {}
@ -873,7 +903,7 @@ fn write_rust_function_shim_impl(
match &arg.ty {
Type::RustBox(_) => write!(out, ".into_raw()"),
Type::UniquePtr(_) => write!(out, ".release()"),
Type::SliceRefU8(_) => write!(out, ")"),
Type::Str(_) | Type::SliceRefU8(_) => write!(out, ")"),
ty if ty != RustString && out.types.needs_indirect_abi(ty) => write!(out, "$.value"),
_ => {}
}
@ -893,7 +923,7 @@ fn write_rust_function_shim_impl(
write!(out, ")");
if !indirect_return {
if let Some(ret) = &sig.ret {
if let Type::RustBox(_) | Type::UniquePtr(_) = ret {
if let Type::RustBox(_) | Type::UniquePtr(_) | Type::Str(_) = ret {
write!(out, ")");
}
}
@ -964,6 +994,7 @@ fn write_extern_return_type_space(out: &mut OutFile, ty: &Option<Type>) {
write_type(out, &ty.inner);
write!(out, " *");
}
Some(Type::Str(_)) => write!(out, "::rust::repr::PtrLen "),
Some(Type::SliceRefU8(_)) => write!(out, "::rust::Slice<uint8_t>::Repr "),
Some(ty) if out.types.needs_indirect_abi(ty) => write!(out, "void "),
_ => write_return_type(out, ty),
@ -976,6 +1007,7 @@ fn write_extern_arg(out: &mut OutFile, arg: &Var) {
write_type_space(out, &ty.inner);
write!(out, "*");
}
Type::Str(_) => write!(out, "::rust::repr::PtrLen "),
Type::SliceRefU8(_) => write!(out, "::rust::Slice<uint8_t>::Repr "),
_ => write_type_space(out, &arg.ty),
}

1
include/cxx.h
View File

@ -79,6 +79,7 @@ public:
~Str() noexcept = default;
private:
friend impl<Str>;
// Not necessarily ABI compatible with &str. Codegen will translate to
// cxx::rust_str::RustStr which matches this layout.
const char *ptr;

4
tests/cxx_gen.rs
View File

@ -18,7 +18,7 @@ fn test_extern_c_function() {
let output = str::from_utf8(&generated.implementation).unwrap();
// To avoid continual breakage we won't test every byte.
// Let's look for the major features.
assert!(output.contains("void cxxbridge05$do_cpp_thing(::rust::Str foo)"));
assert!(output.contains("void cxxbridge05$do_cpp_thing(::rust::repr::PtrLen foo)"));
}
#[test]
@ -28,5 +28,5 @@ fn test_impl_annotation() {
let source = BRIDGE0.parse().unwrap();
let generated = generate_header_and_cc(source, &opt).unwrap();
let output = str::from_utf8(&generated.implementation).unwrap();
assert!(output.contains("ANNOTATION void cxxbridge05$do_cpp_thing(::rust::Str foo)"));
assert!(output.contains("ANNOTATION void cxxbridge05$do_cpp_thing(::rust::repr::PtrLen foo)"));
}