I'm trying to wrap a C++ library and have reduced my problem case to the code below. I get a linker error due to different name mangling (this is on Linux):

main.d:(.text._Dmain+0x13): undefined reference to `_ZN3ns13ns212createStructERN3ns17OptionsE'

The C++ object file has instead a symbol called _ZN3ns13ns212createStructERNS_7OptionsE. To make matters worse and me more confused, according to https://demangler.com, they both demangle to the same thing: `ns1::ns2::createStruct(ns1::Options&)`.

If you're wondering why there's two D files it's because trying to do:

extern(C++, ns1) {... }
extern(C++, ns1.ns2) {...}

doesn't compile since there would be two D versions of ns1, which is... mildly annoying.

I even took `const` off of the parameter in case that was the problem but clearly not.

Atila


impl.cpp:


namespace ns1 {

struct Options {

};

struct Struct {

};

namespace ns2 {
ns1::Struct* createStruct(Options&) {
    return nullptr;
}

}

}


header.d:

extern(C++, ns1) {
    struct Options {

    }

    struct Struct {
    }
}


main.d:

extern(C++, ns1.ns2) {
    import header;
    Struct* createStruct(ref Options);
}


void main() {
    import header;
    Options options;
    auto s = createStruct(options);
}

That's a mangling compression scheme (possibly tunable via gcc options), from https://github.com/gchatelet/gcc_cpp_mangling_documentation:
> To save space a compression scheme is used where symbols that appears multiple times are then substituted by an item from the sequence : S_, S0_, S1_, S2_, etc ...

As to nested C++ namespaces - `extern(C++, ns1) { ... extern(C++, ns2) { ... } }` should work in a single D file.

On Tuesday, 28 March 2017 at 16:30:19 UTC, kinke wrote:
> That's a mangling compression scheme (possibly tunable via gcc options), from https://github.com/gchatelet/gcc_cpp_mangling_documentation:
>> To save space a compression scheme is used where symbols that appears multiple times are then substituted by an item from the sequence : S_, S0_, S1_, S2_, etc ...
>
> As to nested C++ namespaces - `extern(C++, ns1) { ... extern(C++, ns2) { ... } }` should work in a single D file.

Good to know, thanks!

Atila

On Tuesday, 28 March 2017 at 16:30:19 UTC, kinke wrote:
> That's a mangling compression scheme (possibly tunable via gcc options), from https://github.com/gchatelet/gcc_cpp_mangling_documentation:
>> To save space a compression scheme is used where symbols that appears multiple times are then substituted by an item from the sequence : S_, S0_, S1_, S2_, etc ...
>
> As to nested C++ namespaces - `extern(C++, ns1) { ... extern(C++, ns2) { ... } }` should work in a single D file.

Not only good to know, this... fixed it. So I was being stupid. Thanks!

Atila