[CMake] Elegant solution for preprocessing a linker script?

[Williams, Norman K]

Why doesn't this work?

add_custom_command(
OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/api.lds
MAIN_DEPENDENCY ${CMAKE_CURRENT_SOURCE_DIR}/api.lds.S
COMMAND ${CMAKE_C_COMPILER} -E ${CMAKE_CURRENT_SOURCE_DIR}/api.lds.S
        -P -o ${CMAKE_CURRENT_BINARY_DIR}/api.lds.S)

The actual target that needs the linker script needs to depend on api.lds,
or the custom command will never be run, because it lives outside the
dependency chain of the build system.

In other words, if nothing depends on api.lds, it will never get built.

add_dependencies(target_that_actually_depends_on_api_lds
        ${CMAKE_CURRENT_BINARY_DIR}/api.lds)



On 11/6/13 9:01 AM, "Michael Weise" <michael.weise at ek-team.de> wrote:

>Hello,
>
>I'm looking for a way to preprocess a linker script.
>
>After (unsuccessfully) trying add_custom_command() I found this
>explanation and a workaround:
>http://www.mail-archive.com/cmake@cmake.org/msg16496.html
>
>
>It uses an intermediate dependency "dummy.c" in the source list of
>the executable, which forces the custom command to be executed:
>
>----
>add_executable(cmake_test ${CMAKE_CURRENT_BINARY_DIR}/dummy.c)
>
>add_custom_command(
>  OUTPUT  ${CMAKE_CURRENT_BINARY_DIR}/dummy.c
>  COMMAND ${CMAKE_C_COMPILER} -E ${CMAKE_CURRENT_SOURCE_DIR}/api.lds.S
>                              -P -o ${CMAKE_CURRENT_BINARY_DIR}/api.lds
>  COMMAND echo "/* this file is (almost) empty */"
>               > ${CMAKE_CURRENT_BINARY_DIR}/dummy.c
>  MAIN_DEPENDENCY ${CMAKE_CURRENT_SOURCE_DIR}/api.lds.S )
>
>set(CMAKE_EXE_LINKER_FLAGS "-T api.lds")
>----
>
>While this is actually working, I find the approach somehow "dirty".
>Is there a more elegant solution without the dummy.c file?
>
>Best Regards
>Michael
>
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