Merge pull request #2954 from helinwang/cmake_rebuild

cmake: fix problem that go_library is never rebuilt.

Author: helinwang

cmake/generic.cmake

@@ -290,8 +290,22 @@ function(go_library TARGET_NAME)
  set(${TARGET_NAME}_LIB_NAME "${CMAKE_STATIC_LIBRARY_PREFIX}${TARGET_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX}" CACHE STRING "output library name for target ${TARGET_NAME}")
  endif()
 
- # Add dummy code to support `make target_name` under Terminal Command
  set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/${TARGET_NAME}_dummy.c)
+
+ # This custom command will always run since it depends on a not
+ # existing file.
+ add_custom_command(
+ OUTPUT dummy_rebulid_${TARGET_NAME}
+ COMMAND cmake -E touch ${dummyfile}
+ )
+ # Create a custom target that depends on the custom command output
+ # file, so the custom command can be referenced as a dependency by
+ # `add_dependencies`.
+ add_custom_target(rebuild_${TARGET_NAME}
+ DEPENDS dummy_rebulid_${TARGET_NAME}
+ )
+
+ # Add dummy code to support `make target_name` under Terminal Command
  file(WRITE ${dummyfile} "const char * dummy = \"${dummyfile}\";")
  if (go_library_SHARED OR go_library_shared)
  add_library(${TARGET_NAME} SHARED ${dummyfile})
@@ -302,6 +316,12 @@ function(go_library TARGET_NAME)
  add_dependencies(${TARGET_NAME} ${go_library_DEPS})
  endif(go_library_DEPS)
 
+ # The "source file" of the library is `${dummyfile}` which never
+ # change, so the target will never rebuild. Make the target depends
+ # on the custom command that touches the library "source file", so
+ # rebuild will always happen.
+ add_dependencies(${TARGET_NAME} rebuild_${TARGET_NAME})
+
  set(${TARGET_NAME}_LIB_PATH "${CMAKE_CURRENT_BINARY_DIR}/${${TARGET_NAME}_LIB_NAME}" CACHE STRING "output library path for target ${TARGET_NAME}")
 
  file(GLOB GO_SOURCE RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "*.go")