[cmake-developers] [CMake 0012929]: The "-shared" gcc option is not provided for MODULE shared library if PROJECT command declares in ways

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
====================================================================== 
http://www.cmake.org/Bug/view.php?id=12929 
====================================================================== 
Reported By:                Zheng GONG
Assigned To:                
====================================================================== 
Project:                    CMake
Issue ID:                   12929
Category:                   CMake
Reproducibility:            always
Severity:                   minor
Priority:                   low
Status:                     new
====================================================================== 
Date Submitted:             2012-02-02 18:52 EST
Last Modified:              2012-02-02 18:52 EST
====================================================================== 
Summary:                    The "-shared" gcc option is not provided for MODULE
shared library if PROJECT command declares in ways
Description: 
The "-shared" gcc option is not provided for MODULE shared library, if PROJECT
command declares in some ways.

test cases:
PROJECT (${proj_name})         - OK
PROJECT (${proj_name}C CXX)    - OK
without PROJECT command        - OK
PROJECT (${proj_name}CXX)      - FAIL
PROJECT (${proj_name}CXX C)    - FAIL

CMAKE_SHARED_MODULE_CREATE_C_FLAGS gets its initial value in
CMakeCInformation.cmake from CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS.

It seems that if CMakeCXXInformation.cmake is called before
CMakeCInformation.cmake, The variable CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS will
take the default value of CMAKE_SHARED_MODULE_CREATE_C_FLAGS which is blank at
that moment. 

As shown in CMakeCXXInformation.cmake files:
161 # repeat for modules
162 IF(NOT CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS)
163   SET(CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS
${CMAKE_SHARED_MODULE_CREATE_C_FLAGS})
164 ENDIF(NOT CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS)


The "-shared" gcc option is provided for SHARED library in any case.

Since CMakeGenericSystem.cmake gives CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS default
value "-shared". And in CMakeCXXInformation.cmake, '-shared' is passed to
CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS.


Steps to Reproduce: 
CMakeLists.txt file:
PROJECT (test CXX)
ADD_LIBRARY(a MODULE a.cpp)

a.cpp file:
int a(void){ return 0;
}

compile with MinGW, related log:
Linking CXX shared module liba.dll
C:\cmake-2.8.7-win32-x86\bin\cmake.exe -E cmake_link_script
CMakeFiles\a.dir\link.txt --verbose=1
C:\cmake-2.8.7-win32-x86\bin\cmake.exe -E remove -f CMakeFiles\a.dir/objects.a
C:\MinGW\bin\ar.exe cr CMakeFiles\a.dir/objects.a @CMakeFiles\a.dir\objects1.rsp
C:\MinGW\bin\g++.exe      -o liba.dll
-Wl,--major-image-version,0,--minor-image-version,0 -Wl,--whole-archive
CMakeFiles\a.dir/objects.a -Wl,--no-whole-archive -lkernel32 -luser32 -lgdi32
-lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 
c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../libmingw32.a(main.o): In function
`main':
C:\MinGW\msys\1.0\src\mingwrt/../mingw/main.c:73: undefined reference to
`WinMain at 16'

in which, CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS is empty rather than '-shared'
which cause the failure.

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Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2012-02-02 18:52 Zheng GONG     New Issue                                    
======================================================================