[CMake] file depending on a target

[Brad King]

Brandon J. Van Every wrote:
> How can I make a file depend on a target?  I have a lexer SILEX.EXE that 
> I generate.  I need other files to depend on the existence of SILEX.EXE, 
> so that I can lex and create new output.  It seems like 
> target-depends-on-target is dealt with, and file-depends-on-file, and 
> even target-depends-on-file.  But not file-depends-on-target.
> 
> My current headscratching code:
> 
> EXE_C_TARGET(silex) # Generates silex.c from silex.scm
> ADD_EXECUTABLE(silex ${Chicken_BINARY_DIR}/silex.c)
> SET_TARGET_PROPERTIES(silex PROPERTIES COMPILE_FLAGS "${STATIC_FLAGS}")
> TARGET_LINK_LIBRARIES(silex libchicken-static)
> 
> ADD_CUSTOM_COMMAND(
>  OUTPUT ${Chicken_BINARY_DIR}/easyffi.l.silex
>  MAIN_DEPENDENCY ${Chicken_SOURCE_DIR}/easyffi.l
>  DEPENDS silex
>  COMMAND silex ${Chicken_SOURCE_DIR}/easyffi.l 
> ${Chicken_BINARY_DIR}/easyffi.l.silex
> )
> 
> ADD_FILE_DEPENDENCIES(${Chicken_BINARY_DIR}/easyffi.c
>  ${Chicken_BINARY_DIR}/easyffi.l.silex
> )
> 
> 
> It seems that "DEPENDS silex" will not refer to the SILEX.EXE target.  
> Rather, it thinks it's an ordinary file level dependency.

That's okay.  The make process that evaluates the file-level dependency 
will not be executed until it is known that the exe target is up to 
date.  That is what the target-level dependency does.

-Brad