I am getting linker failures under MinGW, however I cannot see why. This is the link command:
g++ -shared -mthreads -Wl,--out-implib,C:\Users\camm\Syren\libs\libSy_polyMesh.a -o C:\Users\camm\Syren\libs\Sy_polyMesh.dll debug/Sy_polyMesh.o debug/moc_Sy_polyMesh.o debug/qrc_Sy_polyMesh.o -L"c:\Qt\4.8.4\lib" -lglu32 -lopengl32 -lgdi32 -luser32 -LC:\Users\camm\Syren/libs -lSyren -lglew32 -lboost_system -lQtSvgd4 -lQtSqld4 -lQtOpenGLd4 -lQtGuid4 -lQtCored4
The undefined reference errors come from the Syren dll (I should state the command was automatically generated by qmake). The -LC:\Users\camm\Syren/libs looks malformed to me because of the mix of forward and backslashes, but if I manually set them to all one way or the other - it does not change the compiler output.
I had earlier problems with 3rd party libraries I needed (GLEW and Boost specifically), but because they were relatively 'constant' I didn't have a problem putting them in my C:\MinGW\lib directory. But that is really not an option for my plugins.
What I find is that the MinGW docs state in a few locations:
...since suitable search paths may always be specified using -L options.
...but that GCC itself furnishes the effective defaults, by supplying appropriate -L options.
However, C:\Users\camm\Syren\libs is where Syren.dll resides!
Edit: Here are the LIBS declarations in my .pro file:
LIBS += -L$(SYREN_PATH)/libs \
-lSyren
win32 {
LIBS += -lglew32 \
-lboost_system
}
And $(SYREN_PATH) expands to C:\Users\camm\Syren. Also I can see to the 'missing' symbols in Syren.dll, for example:
C:\Users\camm\Documents\Syren\Sy_polyMesh_debug/../Sy_polyMesh/src/Sy_polyMesh.cpp:341: undefined reference to `Sy_GLBuffer::unbind()'
Can be seen listed as:
6c500bd6 T _ZN11Sy_GLBuffer6unbindEv
Edit2
After adding a verbose flag to the linker stage I noticed that the linker was iterating through each search path and then through each library naming convention, and using the first one it could open.
attempt to open C:\Users\camm\Syren/libs/libSyren.dll.a failed
attempt to open C:\Users\camm\Syren/libs/Syren.dll.a failed
attempt to open C:\Users\camm\Syren/libs/libSyren.a succeeded
Hypothesizing that the libSyren.a may be broken, I renamed it to force the linker to use the .dll:
attempt to open C:\Users\camm\Syren/libs/libSyren.dll.a failed
attempt to open C:\Users\camm\Syren/libs/Syren.dll.a failed
attempt to open C:\Users\camm\Syren/libs/libSyren.a failed
attempt to open C:\Users\camm\Syren/libs/Syren.lib failed
attempt to open C:\Users\camm\Syren/libs/libSyren.dll failed
attempt to open C:\Users\camm\Syren/libs/Syren.dll succeeded
But I still get exactly the same error messages!