dll vs static build issues on Windows

[tksharpless]

Twin problems currently prevent using glog on Windows:
1] cmake offers no option to build a dll, creates only a static build
2] glog headers all assume a dll ("__declspec(dllimport)"), there is no check for static. So linking with the static library fails.

[tksharpless]

It is possible to build a dll using the readymade MSVC projects. But not to link glog statically.

[tksharpless]

BUT the readymade projects won't build 64-bit without modification. [AAARRRGH]

[sergiud]

Actually, CMake does offer an option to build DLLs: https://cmake.org/cmake/help/v3.5/variable/BUILD_SHARED_LIBS.html. This option applies to CMake enabled glog as well.

[sergiud]

By the way, as I'm aware that you are trying to build Ceres with glog on Windows, I must note that this is in fact possible. However, this requires minor changes in Ceres' CMakeLists.txt. See cmake/INSTALL.md how to use the CMake version of glog.

[tksharpless]

Thanks Sergiu,

Are you telling me I could get a dll build of glog just by setting a cmake
variable? Then why not offer that option as a checkable item in your cmake
script (I use cmake-gui on Windows and will not edit scripts unless there
is no other way).
I have been able to build ceres with the static glog libraries that the
as-distributed cmake setup makes.
But only by changing this bit of logging.h:

// Annoying stuff for windows -- makes sure clients can import these functions

/// even if they want to use the static library! -- TKS

#ifndef GOOGLE_GLOG_DLL_DECL

if defined(_WIN32) && !defined(CYGWIN)

ifdef GLOG_STATIC

define GOOGLE_GLOG_DLL_DECL

else

define GOOGLE_GLOG_DLL_DECL __declspec(dllimport)

endif

else

define GOOGLE_GLOG_DLL_DECL

endif

#endif

Now defining GLOG_STATIC in all builds does the trick.

-- Tom

On Wed, Apr 20, 2016 at 5:27 AM, Sergiu Deitsch notifications@github.com
wrote:

By the way, as I aware that you are trying to build Ceres with glog on
Windows, I must note that this is in fact possible. However, this requires
minor changes in Ceres' CMakeLists.txt. See cmake/INSTALL.md
http://../tree/master/cmake/INSTALL.md how to use the CMake version of
glog.

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#103 (comment)

[sergiud]

@tksharpless That's correct. Just by calling CMake using ``cmake -DBUILD_SHARED_LIBS:BOOL=ON` will generate a Visual Studio solution that produces DLLs. Unfortunately, CMake chose not to provide a default cache entry for the option which would allow to modify it via cmake-gui. But you can add the option yourself using the above command line call. As a side note, Ceres works with static glog as well.

[dashesy]

When I use this

cmake .. -Dgflags_DIR=/c/devel/gflags/tmp/ -DBUILD_SHARED_LIBS=1

To build glog shared library on Windows I get this error when I try to build the solution:

1>c:\devel\glog\src\stacktrace_windows-inl.h(42): error C2375: 'google::GetStackTrace': redefinition; different linkage

That line is this:

    GOOGLE_GLOG_DLL_DECL
    int GetStackTrace(void** result, int max_depth, int skip_count) {

During build it must be export, during usage it must be import. I think GOOGLE_GLOG_DLL_DECL definition is not complete.

---

Edit: This error is the current master. The release v0.3.5 compiles fine

[sergiud]

@dashesy I can confirm the problem. Can you please create a new issue since this problem is unrelated to the one of the original author? Thanks!