• Abby (24/24) Mar 14 2020 I would like to export some functions from my bettec dll for
• User (2/5) Mar 14 2020 It is the calling convention.
• Mike Parker (13/34) Mar 14 2020 For one thing, you're defining it with stdcall in dotnet, but
• Ahmet Sait (5/7) Mar 15 2020 You can check my library documentation to understand how to do

Abby <loniro7678 twit-mail.com> writes:

I would like to export some functions from my bettec dll for 
dotnet core application in windows.

Right now I have compiled dll using dmd v2.091.0-dirty simply by 
´dub build´

this is the function I have

extern(C) char* test_echo(const(char)* line, size_t len,  ref 
size_t resLen)
{
     enum format = "{\"message\": \"%s\"}\n";

     auto response = cast(char*)malloc(format.length + len);
     resLen = sprintf(response, format, line);
     return response;
}

and this is my dotnet core equivalent

[DllImport(DllName, CallingConvention = 
CallingConvention.StdCall)]
static extern IntPtr 
test_echo([MarshalAs(UnmanagedType.LPStr)]string line, ulong len, 
out ulong resLen);

This works for me in linux but does not in windows, any idea what 
I'm doing wrong?

This is the output from dotnet core

Unhandled exception. System.EntryPointNotFoundException: Unable 
to find an entry point named 'test_echo' in DLL 'test.dll'

User <user user.com> writes:

On Saturday, 14 March 2020 at 20:53:45 UTC, Abby wrote:
 I would like to export some functions from my bettec dll for 
 dotnet core application in windows.

 [...]

It is the calling convention.

Mike Parker <aldacron gmail.com> writes:

On Saturday, 14 March 2020 at 20:53:45 UTC, Abby wrote:
 I would like to export some functions from my bettec dll for 
 dotnet core application in windows.

 Right now I have compiled dll using dmd v2.091.0-dirty simply 
 by ´dub build´

 this is the function I have

 extern(C) char* test_echo(const(char)* line, size_t len,  ref 
 size_t resLen)
 {
     enum format = "{\"message\": \"%s\"}\n";

     auto response = cast(char*)malloc(format.length + len);
     resLen = sprintf(response, format, line);
     return response;
 }

 and this is my dotnet core equivalent

 [DllImport(DllName, CallingConvention = 
 CallingConvention.StdCall)]
 static extern IntPtr 
 test_echo([MarshalAs(UnmanagedType.LPStr)]string line, ulong 
 len, out ulong resLen);

 This works for me in linux but does not in windows, any idea 
 what I'm doing wrong?

For one thing, you're defining it with stdcall in dotnet, but 
cdecl in the code. You should change the convention on the dotnet 
side to CallingConvention.Cdecl. Or, if you really want to use 
stdcall, use extern(System) in D -- the equivalent of 
extern(Windows) on Windows and extern(C) everywhere else.

Also, I would expect you'd have to use export [1] on the D side 
for the symbol to be loadable from the dll:

extern(C) export char* test_echo(...) { ... }

This should be the equivalent of __declspec(dllexport) for C and 
C++ on Windows.

[1] https://dlang.org/spec/attribute.html#visibility_attributes 

Ahmet Sait <nightmarex1337 hotmail.com> writes:

On Saturday, 14 March 2020 at 20:53:45 UTC, Abby wrote:
 I would like to export some functions from my bettec dll for 
 dotnet core application in windows.


You can check my library documentation to understand how to do 

https://github.com/ahmetsait/IDL/wiki

Should probably write a detailed blog post about that some time :/