[CMake] adding dependencies on generated files to source code files

[J Decker]

On Mon, Mar 8, 2010 at 6:28 PM, Tony Bridges <nabridges at gmail.com> wrote:
> Hi All,
>
> The problem is : the files that are generated are not dependencies of the
> top level target (as discussed in the article), they are dependencies of
> another source file because they are generated includes.  If I add the
> dependency to the executable, there’s no guarantee that the order will be
> correct, from what I see.
>

I think pretty much dependencies are handled in-order... unless there
is something specifically that requires something else before the
first thing.



>
>
> i.e.
>
>  message compiler runs in directory A, produces a .txt output containing
> string definitions.
>
>  Generated file is included into an RC file in directory B, within the
> correct RC context.
>
>
>
> The piece I’m missing is how to hook a source file as a top level target,
> without having to reimplement the compilation phase as a custom rule.
>

it does seem that sources are not targets... but the target they are
built into can depend on other targets, which get built before sources
are compiled?

>
>
> The makefile equivalent of all this is very simply :
>
>     myResource.rc : externalGeneratedFile.txt
>
>
>
> This feels like fairly common usage, so I’m sure I’ve just missed something,
> but I’m not sure what.
>
> many thanks
>

I was just playing with this...

cmake_minimum_required(VERSION 2.8)

set( FAKE source.h )

#this would be text->.h
add_custom_command( OUTPUT source.h
                     #DEPENDS ${SACK_BASE}/all_resources.rc
                     COMMAND echo \#include \"stdio.h\" >source.h
 )

# this would be .h used by
add_custom_command( OUTPUT main.c
                     DEPENDS source.h
                     COMMAND echo int main( void ) { return 1\; } >main.c
 )

ADD_CUSTOM_TARGET( generate_foo DEPENDS main.c )

# have to touch filea.c fileb.c and filec.c yourself... for brevity...
set( SOURCES main.c filea.c fileb.c filec.c )

add_executable( main ${SOURCES} )
# this pretty much makes sure that the header is generated before
other tings are compiled.
add_dependencies( main generate_foo )


# output after a make clean...
[  0%] Generating source.h
[  0%] Generating main.c
[ 25%] Built target generate_foo
[ 37%] Building C object CMakeFiles/main.dir/main.c.obj
[ 50%] Building C object CMakeFiles/main.dir/a.c.obj
[ 62%] Building C object CMakeFiles/main.dir/b.c.obj
[ 75%] Building C object CMakeFiles/main.dir/c.c.obj
Linking C executable main.exe
[100%] Built target main

# next output...
M:\tmp\zz\zz>make
[ 25%] Built target generate_foo
[100%] Built target main


> /t
>
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