[CMake] Why does a mylib.dll.a file be build automatically ?

[Kermit Mei]

Hello, I use cmake with Qt4.5.0(for Win installer), and my program on
can be compiled well on Linux, but when I use in windows, I want a share
lib, but it always build a mylib.dll.a file with mylib.dll. And finally,
when I link the targets, it can't work, and tell me:
Linking CXX shared library ..\..\lib\libFreeReciteGui.dll
...(some undefined errors)...

I detected the lib directory, and libFreeReciteGui.dll haven't been
built, but a libFreeReciteGui.dll be built. Why?
The CMakeLists.txt for this library is:
###########################################
##$ cat ../src/gui/CMakeLists.txt 
###########################################
# Include the core library.
INCLUDE_DIRECTORIES(${FREERECITE_SOURCE_DIR}/src/core)
# Make sure the compiler can find include files from our ui library.
INCLUDE_DIRECTORIES(${FREERECITE_BINARY_DIR}/src/gui)
# Make sure the linker can find the ui library once it is built.
LINK_DIRECTORIES(${FREERECITE_BINARY_DIR}/lib)

SET(LIBRARY_OUTPUT_PATH ${CMAKE_BINARY_DIR}/lib)

# with SET() command you can change variables or define new ones
# here we define SAMPLE_SRCS variable that contains a list of all .cpp
files
# note that we don't need \ at the end of line
SET( FR_SRCS
    Speaker.h
    Speaker.cpp
    )

SET( FRGUI_SRCS
  AddDialog.cpp
  MainWindow.cpp
  MainWidget.cpp
  ModifyDialog.cpp
  TaskModel.cpp
  ScannerWidget.cpp
  ReciterWidget.cpp
  ResultWidget.cpp
  TesterWidget.cpp
  )
  
# another list, this time it includes all header files that should be
treated with moc
SET( FRGUI_MOC_HDRS
  AddDialog.h
  MainWindow.h
  MainWidget.h
  ModifyDialog.h
  TaskModel.h
  ScannerWidget.h
  ReciterWidget.h
  ResultWidget.h
  TesterWidget.h
  )

# some .ui files
SET( FRGUI_UIS
  AddDialog.ui
  MainWindow.ui
  MainWidget.ui
  ModifyDialog.ui
  ResultWidget.ui
  ScannerWidget.ui
  )

# and finally an resource file
#SET( FRGUI_RCS
#  ./src/rc/sample.qrc
#  )

# enable warnings
ADD_DEFINITIONS( -Wall )
  
# by default only QtCore and QtGui modules are enabled
# other modules must be enabled like this:

#SET( QT_USE_QT3SUPPORT TRUE )   

#SET( QT_USE_QTXML TRUE )

# this command finds Qt4 libraries and sets all required variables
# note that it's Qt4, not QT4 or qt4
FIND_PACKAGE( Qt4 REQUIRED )

SET( QT_USE_QTWEBKIT TRUE )

# add some useful macros and variables
# (QT_USE_FILE is a variable defined by FIND_PACKAGE( Qt4 ) that
contains a path to CMake script)
INCLUDE( ${QT_USE_FILE} )

# this command will generate rules that will run rcc on all files from
FRGUI_RCS
# in result FRGUI_RC_SRCS variable will contain paths to files produced
by rcc
#QT4_ADD_RESOURCES( FRGUI_RC_SRCS ${FRGUI_RCS} )

# this will run uic on .ui files:
QT4_WRAP_UI( FRGUI_UI_HDRS ${FRGUI_UIS} )

# and finally this will run moc:
QT4_WRAP_CPP( FRGUI_MOC_SRCS ${FRGUI_MOC_HDRS} )

ADD_LIBRARY(FreeReciteGui SHARED
  ${FRGUI_SRCS}
  ${FRGUI_MOC_SRCS}
  ${FRGUI_UI_HDRS}
  ${FR_SRCS}
  )

TARGET_LINK_LIBRARIES(FreeReciteGui FreeReciteCore ${QT_LIBRARIES})

INSTALL(TARGETS LIBRARY DESTINATION lib)
###########################################

And by the way, it works well on Linux. Another share library is
FreeReciteCore.dll, and it also be built on Windows.

Help me, please;p
Thanks for any replay!
Kermit