GeoExpress DSDK and MinGW / GCC

kshehata · Joined: 08 Mar 2010 Posts: 14

I've now gotten my JNI library to load in the MrSID data and I can display it on my Mac and Linux, and now I'm looking to add it to our windows build. We use MinGW / GCC to build our windows executables. Is there a build of the DSDK available for that environment?

I've tried using the VC9 build. I can get it to compile a .o file by adding a few defines to headfake lt_platform.h into thinking that the compiler is visual studio, but I can't get past linking. The linker seems to recognize the .lib files, but it complains of all kinds of undefined references. Any ideas?

Thanks!

Kareem

kshehata · Joined: 08 Mar 2010 Posts: 14

Here's the output from linking:
h_t_t_p://pastebin.com/wJSRJ11z

gat · Joined: 12 Jan 2009 Posts: 27

I'm sorry but we do not have a distribution for that compiler.

kirkoman · Joined: 24 Jan 2008 Posts: 11 Location: LizardTech

Kareem,

The undefined symbols in your listing should be coming from msvcrt or libc (or corresponding threaded/debug versions of the same). Could they have to do with the warnings up at the front? For example:

Warning: .drectve `/DEFAULTLIB:"libcpmt" /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized

I'm not super familiar with the mingw environment, but libcmt is where these symbols should be coming from, so if it is not getting linked in that may be your problem.

Kirk

kshehata · Joined: 08 Mar 2010 Posts: 14

[quote="gat"]I'm sorry but we do not have a distribution for that compiler.[/quote]

How do people build JNI interfaces for multiple platforms then? I'm trying to have a Java JAR and a set of libraries that work consistently across Windows, Mac, and Linux, and it's a whole lot easier to do that with gcc than switching compilers.

Also: our build server is on Linux, so I'd have to change our entire build system to use the Visual Studio compiler. That's really not an option for us.

kshehata · Joined: 08 Mar 2010 Posts: 14

Based on the discussion on StackOverflow (link below, I don't understand why BB code isn't working), it looks like linking from one compiler to another is simply impossible. This is a dealbreaker for us: we have make this work on Windows, or the whole effort is lost. Is there any chance of having a version compiled with MinGW? If you already have a linux build script, this should be trivially easy to do. If not, how do people build JNI libraries for multiple platforms?

h_t_t_p://stackoverflow.com/questions/1796209/how-to-link-to-vs2008-generated-libs-from-g

kshehata · Joined: 08 Mar 2010 Posts: 14

Confirmed: you cannot link C++ libraries built with one compiler to another.

h_t_t_p://stackoverflow.com/questions/2472924/linking-to-msvc-dll-from-mingw

BTW: Have you considered releasing a Java interface? Even if it required a platform specific library (.dll/.so/.dylib), the JNI layer on top of what you have should be pretty easy to do. Considering that I started with nothing less than two weeks ago and can now view SID-based map data and I've integrated it with our existing GUI, a full implementation should be quick and high value.

kirkoman · Joined: 24 Jan 2008 Posts: 11 Location: LizardTech

I've looked into building our SDK using MinGW and it is not as trivial as one would think. Just as you would have to "change [your] entire build system" to use the VS compiler, we have a pretty hefty build-server system in place which serves its purpose well but adding new platforms is a significant process with a lot of setup and hand-holding.

I would love to see this platform get supported, and will escalate your request. However, this is the only request we have received for mingw support, so even if it does happen, it is not likely to be in a short timeframe. So I'd recommend pursuing your only viable option at this point: Either use the existing C DLL (which is fairly simplistic, I know), or write a VS shim DLL (i.e., roll your own C DLL that meets your needs).

If you're so inclined, I hope you post back once you get something working. Best of luck.

kshehata · Joined: 08 Mar 2010 Posts: 14

I ended up switching over to the plain C library and got that to build successfully on all platforms. Since all I'm looking for is the image data and georeferences, this does the trick.

I'm surprised no one else has run into this. It seems like the most natural way to develop cross platform: use gcc for everything! Then again, I guess most people don't do a lot of cross-platform development.

Thanks for your attention on this. If you do decide to implement a MinGW build, I would definitely be interested in testing it out.

barndt · Joined: 27 Jul 2010 Posts: 2

I am in the same boat. I've been struggling with this for a couple hours now, before I finally stumbled across this post. I'd like to try moving to the C dll as well, but for the life of me I can't find it. Looking on the SDK download page, all I see for Windows is C++ SDKs. Is there something I'm missing? Is the C API somehow bundled with the C++ ones? Are there examples somewhere that use the C API?

Thanks,
Brad

barndt · Joined: 27 Jul 2010 Posts: 2

Nevermind, I think I just found my answer in the /include/c_api directory