Re: LNK2019 error in the C++ interface

[dokutoku via Digitalmars-d-learn]

On Thursday, 10 June 2021 at 15:19:27 UTC, kinke wrote:

Confirmed: https://issues.dlang.org/show_bug.cgi?id=22014


Thank you for the bug report. I'm glad I couldn't handle it 
myself.


The only thing that bothers me is that there is no sign of this 
problem being fixed.

I fear that this may be the case forever.

On Thursday, 10 June 2021 at 15:19:27 UTC, kinke wrote:
Wrt. `tagRECT`, this should come in handy (for a druntime fix): 
https://dlang.org/changelog/2.097.0.html#pragma-mangle-aggregate


I don't see how this helps with the modifications related to 
tagRECT.

Re: LNK2019 error in the C++ interface

[kinke via Digitalmars-d-learn]

On Thursday, 10 June 2021 at 13:19:34 UTC, dokutoku wrote:
The reason seems to be that WCHAR should be mangled with 
wcha_t, but it is mangled with chat16_t.


Confirmed: https://issues.dlang.org/show_bug.cgi?id=22014

Wrt. `tagRECT`, this should come in handy (for a druntime fix): 
https://dlang.org/changelog/2.097.0.html#pragma-mangle-aggregate

Re: LNK2019 error in the C++ interface

[Mike Parker via Digitalmars-d-learn]

On Thursday, 10 June 2021 at 13:19:34 UTC, dokutoku wrote:


I still haven't solved this problem.


Not sure if this is the issue, but you don't need `extern` on 
these. You already have the `extern(C++)` thing at the top of the 
file.


```d
extern void str_test(LPCSTR str1);

nothrow @nogc
extern void wstr_test(LPCWSTR str1);
```

Re: LNK2019 error in the C++ interface

[dokutoku via Digitalmars-d-learn]

It's been a while since then, but the problem with the structure 
has been solved.
The reason seems to be that the structure name defined in 
core.sys.windows.windef was not tagRECT.
I was able to get it to compile by adding a custom definition as 
follows


```d
extern (C)
struct tagRECT
{
LONG left;
LONG top;
LONG right;
LONG bottom;
}

alias RECT = tagRECT;
```

The type name did not work.
The reason seems to be that WCHAR should be mangled with wcha_t, 
but it is mangled with chat16_t.
Since the mangle is wchat_t, I thought maybe I should use wchar_t 
in core.stdc.stdef, so I changed LPCWSTR to const (wchar_t)*, but 
that didn't work either.


I still haven't solved this problem.
I also took a look at Data Type Compatibility in Interfacing to 
C++, and I think it's wrong about wchar_t.


https://dlang.org/spec/cpp_interface.html#data-type-compatibility

LNK2019 error in the C++ interface

[dokutoku via Digitalmars-d-learn]

I tried to use a function from a library written in C++ in D. 
I've been trying to use it in D. But I got an error in LNK2019 
and the build failed.


So I created a simple static library as follows and built it.

```cpp
#pragma once

#include 

namespace static_test {
void str_test(LPCSTR str)
{
MessageBoxA(NULL, str, NULL, MB_OK);
}

void wstr_test(LPCWSTR str)
{
MessageBoxW(NULL, str, NULL, MB_OK);
}

void rect_test(RECT rect)
{
}
}
```

```d
import core.sys.windows.windows;
import std.utf;

extern (C++, "static_test") {
nothrow @nogc
extern void str_test(LPCSTR str1);

nothrow @nogc
extern void wstr_test(LPCWSTR str1);

nothrow @nogc
void rect_test(RECT rect);
}

void main()
{
str_test(toUTFz!(const char*)("test"));

// error LNK2019
wstr_test(toUTF16z("test"w));

// error LNK2019
rect_test(RECT.init);
}
```

The LNK2019 error still occurred.
I'm guessing that the reason for the error is that the type 
declared in C++ is different from the type declared in D. But I'm 
not sure how to fix it.