[CMake] CMake+QT always failed for the first build, and succeeded for second build or later.

Wed Jun 1 03:02:41 EDT 2016

Hej,

Some things that come to mind:
* You're generating files *inside* the source tree - you're not supposed to
do that
* Why do you want to have a special Qt_tmp directory? I don't see the
benefit, and without that requirement you can simply use the qt4_wrap_cpp
macro explicitly and you still are not forced to use the automoc feature

And now for what is probably wrong in your CMakeLists.txt:
* It seems you made an important mistake regarding the behaviour of
'file(GLOB)'. That function will do the expansion *while running CMake*.
But at that time the moc_* files *don't exist!* (as a matter of fact, the
tmp directory doesn't even exist). In other words, your ${Moc_SOURCES} will
be empty, and hence they are not compiled, and hence you get precisely the
linker errors you see (because these sources implement the functions that
are listed as missing by the linker)

If you would use the qt4_wrap_cpp() macro you don't run into this problem,
so I'd strongly suggest using it.

Sincerely,
Jakob van Bethlehem

On Tue, May 31, 2016 at 4:52 PM, irene w <ire866306 at gmail.com> wrote:

> It seems CMakw could not find the generated moc_xxx files.  I modified the
> scripts to specify moc_xxx files is generated, but it still has same errors.
>
> ADD_CUSTOM_COMMAND ( OUTPUT ${Qt_tmp}/moc_GMWindow.cpp
>                      COMMAND ${QT_MOC_CMD} ${GM_DIR}/GMWindow.h -o
> ${Qt_tmp}/moc_GMWindow.cpp
>                      DEPENDS ${GM_DIR}/GMWindow.h
>                    )
> ADD_CUSTOM_TARGET(generate_foo DEPENDS ${Qt_tmp}/moc_GMWindow.cpp)
> SET_SOURCE_FILES_PROPERTIES(${Qt_tmp}/moc_GMWindow.cpp PROPERTIES
> GENERATED 1)
> SET_PROPERTY(SOURCE ${GM_DIR}/GMWindow.cpp APPEND PROPERTY OBJECT_DEPENDS
> ${Qt_tmp}/moc_GMWindow.cpp)
>
> .....
> add_dependencies (GM generate_foo)
>
>
> Does the Macro  "SET_SOURCE_FILES_PROPERTIES" with "GENERATED"
> setting work for this purposes?  Any help would be greatly appreciated !
>
>
> On Wed, May 25, 2016 at 12:48 PM, irene w <ire866306 at gmail.com> wrote:
>
>> Hi,
>>
>> I am compiling a simple Qt3 application on Linux using CMake. In my case,
>> I need to build moc_xxx files with custom options and output to a specified
>> directory, So, I was not using CAMKE_AUTO macros. My cmake scripts create a
>> "Qt_tmp" directory and output moc_xxx there.
>>
>> It looked it always failed to link the moc_xxx files for the first time
>> build when there is no "Qt_tmp" directory, and succeeded if I ran build
>> again if the "Qt_tmp" directory and moc_xxx files created by the failed
>> build were kept without removing.  However, it'll fail if I delete
>> the "Qt_tmp" directory.
>>
>> Even it failed at the first build, the moc_xxx files were
>> successfully created in the "Qt_tmp" directory.
>>
>> Here is my cmake scripts and the errors I got.  Can anyone help me to
>> figure out the issues? Any help would be greatly appreciated.  Thanks.
>>
>> CMakeLists.txt
>>
>> ---------------------------------------------------------------------------------------------
>> cmake_minimum_required(VERSION 3.4.1)
>> project (GM_Application CXX)
>> SET (CMAKE_SYSTEM_NAME Linux)
>> SET (CMAKE_CXX_COMPILER ${COMPILER_PATH}${CROSS_COMPILE}g++)
>> set (GM_DIR ${CMAKE_CURRENT_SOURCE_DIR})
>> set (QT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/ThirdParty/Qt/4.8.6)
>> LINK_DIRECTORIES (${QT_DIR}/lib)
>> INCLUDE_DIRECTORIES ("${QT_DIR}/include"
>>                      "${GM_DIR}"
>> )
>> ##### Compiling QT moc and ui  #####
>> set (QT_MOC_CMD ${QT_DIR}/bin/moc -I$(QT_DIR)/mkspecs/linux-g++
>> -I${QT_DIR}/include -I${QT_DIR}/include/QtGui)
>> file (MAKE_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/Qt_tmp)
>> set (Qt_tmp ${CMAKE_CURRENT_SOURCE_DIR}/Qt_tmp)
>> add_custom_target (Moc_GMWindows
>>                    COMMAND ${QT_MOC_CMD} ${GM_DIR}/GMWindow.h -o
>> ${Qt_tmp}/moc_GMWindow.cpp
>>                   )
>>
>> ##### Compiling application  #####
>> file (GLOB GM_SOURCES ${GM_DIR}/*.h ${GM_DIR}/*.cpp)
>> file (GLOB Moc_SOURCES ${Qt_tmp}/*.h ${Qt_tmp}/*.cpp)
>> add_executable (GM ${GM_SOURCES} ${Moc_SOURCES})
>> target_include_directories (GM PRIVATE ${Qt_tmp})
>> add_dependencies (GM Moc_GMWindows)
>> target_link_libraries (GM QtGui)
>>
>>
>> -------------------------------------------------------------------------------------------
>> Errors:
>>
>> Scanning dependencies of target Moc_GMWindows
>> [  0%] Built target Moc_GMWindows
>> Scanning dependencies of target GM
>> [ 14%] Building CXX object GM/CMakeFiles/GM.dir/GM/GM.cpp.o
>> [ 42%] Building CXX object GM/CMakeFiles/GM.dir/GM/GMService.cpp.o
>> [ 67%] Building CXX object GM/CMakeFiles/GM.dir/GM/GMWindow.cpp.o
>> [ 85%] Building CXX object GM/CMakeFiles/GM.dir/GM/main.cpp.o
>> [100%] Linking CXX executable ../bin/GM
>> CMakeFiles/GM.dir/GM/GMWindow.cpp.o: In function
>> `GM::GMWindow::emitAppendMessage(QStrin
>> g)':
>> /GM/GMWindow.cpp:217: undefined reference to
>> `GM::GMWindow::appendMessage(QString)'
>> CMakeFiles/GM.dir/GM/GMWindow.cpp.o:(.rodata._ZTVN2GM8GMWindowE[vtable
>> for GM::GMWindow]
>> +0x8): undefined reference to `GM::GMWindow::metaObject() const'
>> CMakeFiles/GM.dir/GM/GMWindow.cpp.o:(.rodata._ZTVN2GM8GMWindowE[vtable
>> for GM::GMWindow]
>> +0xc): undefined reference to `GM::GMWindow::qt_metacast(char const*)'
>> CMakeFiles/GM.dir/GM/GMWindow.cpp.o:(.rodata._ZTVN2GM8GMWindowE[vtable
>> for GM::GMWindow]
>> +0x10): undefined reference to
>> `GM::GMWindow::qt_metacall(QMetaObject::Call, int, void**)'
>> collect2: ld returned 1 exit status
>> make[2]: *** [bin/GM] Error 1
>> make[1]: *** [GM/CMakeFiles/GM.dir/all] Error 2
>> make: *** [all] Error 2
>>
>>
>>
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free.
>> www.avast.com
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>
>> <#m_3542150497808946122_m_6400203814648417669_DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>
>
>
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