• Jan (42/42) Dec 06 2021 I am trying to auto-generate bindings for C++ code in D. I've
• frame (3/5) Dec 08 2021 Sounds like a bug to me, eg this one:
• frame (4/9) Dec 08 2021 But this is no show stopper, you can always force the mangling
• Jan (8/19) Dec 09 2021 Oh it's a known bug for over a year already :(

Jan <Jan Krassnigg.de> writes:

I am trying to auto-generate bindings for C++ code in D. I've 
come across something that looks like a bug in DMD to me, but 
since I'm such a newbie in D maybe I am missing something.

My C++ class looks like this:

```cpp
template <typename Type>
struct Vec3Template
{
   static const Vec3Template<Type> ZeroVector();
};
```

And my D binding code looks like this:

```cpp
extern(C++) struct Vec3Template(TYPE)
{
   static const(Vec3Template!(TYPE)) ZeroVector();
}
alias Vec3 = Vec3Template!(float);
```

However, when I try to use Vec3.ZeroVector() I am getting a 
linker error about unresolved symbols. It works with other 
functions, the error is specific to this function.

Now it complains that it can't find this one:
`?ZeroVector ?$Vec3Template M  SA?AU1 XZ`

However, I am using castXml to extract my C++ information, and 
that says that the mangled name should be:
`?ZeroVector ?$Vec3Template M  SA?BU1 XZ`

Running both names through undname.exe, an MSVC tool that 
generates the undecorated function name from the mangled name, it 
says that the latter function definition should be:
`public: static struct Vec3Template<float> const __cdecl 
Vec3Template<float>::ZeroVector(void)`

Whereas the former definition would be:
`public: static struct Vec3Template<float> __cdecl 
Vec3Template<float>::ZeroVector(void)`

So the one that D tries to link against is missing the `const`.

However, unless I misunderstood how to apply const to a type in 
D, you can see that I did wrap the type in const(). (I also tried 
immutable, but that's not allowed for extern C++ code).

So am I missing something, or did the compiler somehow forget 
about the const-ness?

I'm currently using DMD64 D Compiler v2.098.0-dirty

frame <frame86 live.com> writes:

On Monday, 6 December 2021 at 20:31:47 UTC, Jan wrote:

 So am I missing something, or did the compiler somehow forget 
 about the const-ness?

Sounds like a bug to me, eg this one:
https://issues.dlang.org/show_bug.cgi?id=20685

frame <frame86 live.com> writes:

On Thursday, 9 December 2021 at 07:41:32 UTC, frame wrote:
 On Monday, 6 December 2021 at 20:31:47 UTC, Jan wrote:

 So am I missing something, or did the compiler somehow forget 
 about the const-ness?

 Sounds like a bug to me, eg this one:
 https://issues.dlang.org/show_bug.cgi?id=20685

But this is no show stopper, you can always force the mangling 
with the pragma directive.
https://dlang.org/spec/pragma.html#mangle

Jan <Jan Krassnigg.de> writes:

On Thursday, 9 December 2021 at 07:58:46 UTC, frame wrote:
 On Thursday, 9 December 2021 at 07:41:32 UTC, frame wrote:
 On Monday, 6 December 2021 at 20:31:47 UTC, Jan wrote:

 So am I missing something, or did the compiler somehow forget 
 about the const-ness?

 Sounds like a bug to me, eg this one:
 https://issues.dlang.org/show_bug.cgi?id=20685

 But this is no show stopper, you can always force the mangling 
 with the pragma directive.
 https://dlang.org/spec/pragma.html#mangle

Oh it's a known bug for over a year already :(

It is a bit of a show stopper for me, since the mangled name that 
I have isn't always correct (CastXML uses Clang and that seems to 
pick different calling conventions sometimes, than what MSVC 
would do, so the mangled names that I get are not guaranteed to 
be correct).

Well, I'll work around it for now, thanks for the answer.