[CMake] Embedding up-to-date version info in built library

[Kolja Waschk]

> the list of sources. But another problem came up: Only the first single
> list item seems to be scanned for implicit dependencies. And I failed to
> come up with a list or command syntax that would allow me to have the
> other 99+ sources scanned as well.

I think I came up with a usable workaround for now. A semaphore file is
created for every source file which IMPLICIT_DEPENDS on that source
file, and my actual version.cc now depends on all the semaphore files.

Basically this:


foreach (srcfile ${SOURCEFILES})
   string(REPLACE "/" "_" srcok ${srcfile})
   set(semafile dep_${srcok})
   add_custom_command(
     OUTPUT ${semafile}
     COMMAND touch ${semafile}
     IMPLICIT_DEPENDS CXX ${PROJECT_SOURCE_DIR}/src/${srcfile}
     COMMENT ""
   )
   set(VERSION_DEPFILES ${VERSION_SEMAFILES} ${semafile})
endforeach(srcfile)

add_custom_command(
   OUTPUT version.cc
   COMMAND create_version_cc.sh
   DEPENDS ${VERSION_SEMAFILES}
)

I'm open for improvements and better ideas...

Kolja