Is cmake work differently for Linux and WinCE platform? - linux

Question

We are working on the Project which contains thousands of the cmake files. Code is develop on the Linux platform. Now we are porting this project for Windows CE platform.
We are facing lots of linking error when change some of the functionality to project in Linux platform.
We are resolving this linking error by adding respective library in target_link_library of cmake file.
I am surprised how it worked for Linux? And it is failing for Windows CE.
Difference between the platform additional library :
Linux Platform
[A.Common]
[B]
[C]
[C]
[C]
[TLV]
[D]
[Boost.Filesystem]
[Boost.System]
[Boost.Thread]
[Boost.Atomic]
[Boost.DateTime]
[Boost.Chrono]
[Platform.Socket]
[D]
[C]
[C]
[Debug]
[SQLite]
[C]
[C]
[C]
[Meta]
[E]
WinCE
[A.Common]
[B]
[E]
[E]
[E]
[TLV]
[D]
[Boost.Filesystem]
[Boost.System]
[Boost.Thread]
[Boost.Atomic]
[Boost.DateTime]
[Boost.Chrono]
[Platform.Socket]
[D]
[C]
[C]
[Debug]
[SQLite]
[ZLib]
[C]
[C]
[C]
[Meta]
[E]
Any help will be appreciated.

Answer 1

From my experience I can confirm that moving with a CMake project to a new platform is also a check if you have setup your library dependencies correctly.
If we are talking about SHARED libraries, please first confirm that you have correctly exported your function declarations:
Creating and using shared libraries with different compilers on different operating systems
cmake link shared library on Windows
If you are using STATIC libraries, I see two possible approaches (not taking linker errors about missing symbols from system libraries into account):
You may have some if statements checking for this or that platform in your CMake code. So first check that your library dependencies are truly the same by activating GLOBAL_DEPENDS_DEBUG_MODE:
set_property(GLOBAL PROPERTY GLOBAL_DEPENDS_DEBUG_MODE 1)
Put it in your main CMakeList.txt file and compare the output on both platforms.
The linking order is also important, not only that the library is named somewhere on the linker command line. I like to quote from the Beginner's Guide to Linkers:
Another important detail to note is the order of events; the libraries are consulted only when then the normal linking is done, and they are processed in order, left to right. This means that if an object pulled in from a library late in the link line needs a symbol from a library earlier in the link line, the linker won't automatically find it.
Use the following CMake test program to see if your linker does a multi-path scan for open symbols. I've tested it with GCC 4.8.1 (doesn't work) and Visual Studio 2013 (does work). So I don't have your environments, so please do the test yourself.
The program is deliberately setup to have a wrong library linkage order by not using normal library dependencies like target_link_libraries(lib1 lib2) (a rule of thumb is to add as dependecies all libraries you directly include a header file from), but by giving the order in a global list to main:
cmake_minimum_required(VERSION 2.8)
project(WrongLinkOrderTest CXX)
set(_idx 1)
while (_idx LESS 10)
math(EXPR _next_idx "${_idx} + 1")
file(WRITE lib${_idx}.h "int lib${_idx}_func();")
file(WRITE lib${_idx}.cc "#include \"lib${_next_idx}.h\"\nint lib${_idx}_func() { return lib${_next_idx}_func(); }")
add_library(lib${_idx} lib${_idx}.cc)
# NOTE: This would fix it
#target_link_libraries(lib${_idx} lib${_next_idx})
set(_idx "${_next_idx}")
endwhile()
file(WRITE lib${_idx}.h "int lib${_idx}_func();")
file(WRITE lib${_idx}.cc "int lib${_idx}_func() { return 0; }")
add_library(lib${_idx} lib${_idx}.cc)
file(WRITE main.cc "#include \"lib1.h\"\nint main() { return lib1_func(); }")
add_executable(main main.cc)
if (CMAKE_COMPILER_IS_GNUCXX)
#target_link_libraries(main "-Wl,--start-group")
endif()
while (_idx GREATER 0)
math(EXPR _next_idx "${_idx} - 1")
# NOTE: Here it's done wrong
target_link_libraries(main lib${_idx})
set(_idx "${_next_idx}")
endwhile()
if (CMAKE_COMPILER_IS_GNUCXX)
#target_link_libraries(main "-Wl,--end-group")
endif()
By default, it will show the following error with GCC:
liblib1.a(lib1.cc.obj):lib1.cc:(.text+0x7): undefined reference to `lib2_func()'
Uncomment the target_link_libraries(lib${_idx} lib${_next_idx}) or --start-group/--end-group lines to fix it.
Additional References
How do I list the defined make targets from the command line?
Why does the order in which libraries are linked sometimes cause errors in GCC?
GCC: what are the --start-group and --end-group command line options?
Porting code to Windows and getting "error LNK2019: unresolved external symbol ...."
Use -Wl,--start-group and -Wl,--end-group for Android linking