dub, ldc2, MS VS 2015, static c library

[Nicholas Wilson via digitalmars-d-ldc]

On Friday, 16 December 2016 at 03:37:14 UTC, dm wrote:
> Hi!
> I'm trying to build my static c library and use it with my d 
> application.
> I'm making a library as described here: 
> https://msdn.microsoft.com/en-us/library/ms235627(v=vs.90).aspx
>
> My MS VS solution have file funcs.cpp:

                                                       ^^^
> ```
> #include <stdint.h>
>
> int32_t myFunc(int32_t a, int32_t b)
> {
> 	return a + b;
> }
> ```
> I'm build my library. Build is Release, target - x64. Got file 
> mylib.lib.
>
> Next I make app.d:
> ```
> import std.stdio;
>
> extern (C) int myFunc(int, int);
              ^^^
change this to extern(C++)

>
> void main()
> {
> 	writeln(myFunc(1, 2));
> }
> ```
>
> I put mylib.lib in root of my dub project:
> ```
> E:\D\sl>ls
> dub.sdl  mylib.lib  source
>
> E:\D\sl>cat dub.sdl
> name "sl"
> description "A minimal D application."
> libs-windows "mylib"
> libs-posix "mylib"
> dflags "-O5" "-m64" "-release" "-w"
> ```
>
> Next I'm trying to build my app:
> ```
> E:\D\sl>dub build --build=release --compiler=ldc2
>
> ## Warning for package sl ##
>
> The following compiler flags have been specified in the package 
> description
> file. They are handled by DUB and direct use in packages is 
> discouraged.
> Alternatively, you can set the DFLAGS environment variable to 
> pass custom flags
> to the compiler, or use one of the suggestions below:
>
> -m64: Use --arch=x86/--arch=x86_64 to specify the target 
> architecture
> -release: Call dub with --build=release
> -w: Use "buildRequirements" to control warning behavior
>
> Performing "release" build using ldc2 for x86.
> sl ~master: building configuration "application"...
> Using Visual Studio: C:\Program Files (x86)\Microsoft Visual 
> Studio 14.0\
> sl.obj : error LNK2019: unresolved external symbol myFunc 
> referenced in function _Dmain
> .dub\build\application-release-windows-x86-ldc_0-9C4A611E39233F32B4FA0F867429B08B\sl.exe : fatal error LNK1120: 1 unresolved externals
> Error: `C:\Windows\system32\cmd.exe /s /c "C:\ldc\bin\amd64.bat 
> link.exe"` failed with status: 1120
> ldc2 failed with exit code 1120.
> ```
>
> ldc version:
> ```
> E:\D\sl>ldc2 -version
> LDC - the LLVM D compiler (0.17.1):
>   based on DMD v2.068.2 and LLVM 3.7.1
>   Default target: x86_64-pc-windows-msvc
>   Host CPU: ivybridge
>   http://dlang.org - http://wiki.dlang.org/LDC
>
>   Registered Targets:
>     arm      - ARM
>     armeb    - ARM (big endian)
>     cpp      - C++ backend
>     mips     - Mips
>     mips64   - Mips64 [experimental]
>     mips64el - Mips64el [experimental]
>     mipsel   - Mipsel
>     ppc32    - PowerPC 32
>     ppc64    - PowerPC 64
>     ppc64le  - PowerPC 64 LE
>     sparc    - Sparc
>     sparcel  - Sparc LE
>     sparcv9  - Sparc V9
>     thumb    - Thumb
>     thumbeb  - Thumb (big endian)
>     x86      - 32-bit X86: Pentium-Pro and above
>     x86-64   - 64-bit X86: EM64T and AMD64
> ```
>
> What I'm doing wrong?

Your lib is a C++ lib and (because you didn't make myFunc `extern 
"C"`) it has C++ name mangling (_Z6myFunciii or something like 
it). On the D side you said it was extern(C) (_myFunc) therefore 
the linker can't find the symbol because the names don't match.