I use cygwin build a C++ lib file:

libmemcached.a

but, how to link it to my dub project?

On Thursday, 22 September 2016 at 17:09:38 UTC, Brian wrote:
> I use cygwin build a C++ lib file:
>
> libmemcached.a
>
> but, how to link it to my dub project?

should be a .lib under windows. *.a is an archive of object files (aka a static library) for Posix systems. *.lib is the same but for Windows.

On Thursday, 22 September 2016 at 17:09:38 UTC, Brian wrote:
> I use cygwin build a C++ lib file:
>
> libmemcached.a
>
> but, how to link it to my dub project?

You'd probably need to use the GNU linker then, but the D objects would need to match the format used for your C++ lib. You could give the GDC compiler a shot, or use clang to compile the C++ lib to MS COFF format (.lib), which can then be fed to both DMD and LDC on Windows.

On Thursday, 22 September 2016 at 17:09:38 UTC, Brian wrote:
> I use cygwin build a C++ lib file:
>
> libmemcached.a
>
> but, how to link it to my dub project?

I don't know of any D compiler that supports Cygwin. There are older releases of LDC built on top of MinGW and GDC has had some releases for Windows, but I don't believe you'd be able to use anything generated by the Cygwin toolchain with those.

On Thursday, 22 September 2016 at 17:09:38 UTC, Brian wrote:
> I use cygwin build a C++ lib file:
>
> libmemcached.a
>
> but, how to link it to my dub project?

My plan:
1.I use cygwin build libmemcached.dll
2.use def tools export libmemcached.def
3.use VS2015 dev tools convert libmemcached.dll to libmemcached.lib
4.use coffimplib convert libmemcached.lib for D compiler

but, this plan must dep dll file.

how to static link libmemcached.lib?

On Friday, 23 September 2016 at 06:27:20 UTC, Brian wrote:
> how to static link libmemcached.lib?

Just pass the filename to the compiler as if it's a ".d" source and put the path to the sources root with -I

dmd app.d libmemcached.lib -Ipath/to/memcached/interface/

On Friday, 23 September 2016 at 06:27:20 UTC, Brian wrote:
> On Thursday, 22 September 2016 at 17:09:38 UTC, Brian wrote:
>> I use cygwin build a C++ lib file:
>>
>> libmemcached.a
>>
>> but, how to link it to my dub project?
>
> My plan:
> 1.I use cygwin build libmemcached.dll
> 2.use def tools export libmemcached.def
> 3.use VS2015 dev tools convert libmemcached.dll to libmemcached.lib
> 4.use coffimplib convert libmemcached.lib for D compiler
>
> but, this plan must dep dll file.
>
> how to static link libmemcached.lib?

With dub, you can use the the 'libs' directive in your configuration file. See the Build Settings section a [1] if you are using JSON and [2] for SDL. If you manage to get your Cygwin-compiled libs to work with DMD successfully with this approach, please let us know. I was unable to get anything more than simple C libraries compiled by MinGW to work with DMD.

[1] https://code.dlang.org/package-format?lang=json#build-settings
[2] https://code.dlang.org/package-format?lang=sdl#build-settings