[CMake] VC2005 - ADD_CUSTOM_TARGET problems..

[Shishir Ramam]

Brad,
As always, thanks for the quick response.

A few follow ups - 

On 5/26/05, Brad King <brad.king at kitware.com> wrote:
> Shishir Ramam wrote:
> > root/
> >      PROJECT(MyProject)
> >      subdir1/src
> >                      ADD_EXECUTABLE(target1 target1_srcs.c)
> >                      # target1 generates a header file - say gen_header.h
> >      subdir2/
> >                 ADD_EXECUTABLE(target2 target2_srcs.c)
> >
> > target2 includes gen_header.h So my interest is in building and running target1
> > before attempting to build target2.
> 
> This is a common design and is fully supported by CMake, but not quite
> the way you are doing things.  The custom command for generating the
> header should be added in subdir2/CMakeLists.txt:
> 
> ADD_CUSTOM_COMMAND(
>    OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/gen_header.h
>    COMMAND ${EXE_DIR}/target1 ARGS arg1 arg2
>    DEPENDS ${EXE_DIR}/target1
> )

What is the purpose of OUTPUT here? I'm guessing it allows Cmake to 
determine dependencies.

> 
> Since the header is generated it will not exist when the dependencies of
> the source files are scanned, so you need to add the dependency using a
> source file property:
> 
> SET_SOURCE_FILES_PROPERTIES(target2_src.c
>    PROPERTIES OBJECT_DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/gen_header.h)

This does seem reasonable. The complication that arose for my project
was the gen_header.h is also used for a few other targets in root/subdir1,
root/subdir2, root/subdir3. 

Instead of adding the dependency for each source file, I was attempting
sequence the steps, such that - 
1. target1 gets built, 
2. gen_header.h gets generated via a ADD_CUSTOM_TARGET with the ALL option. 
3. All the other targets can get built from there without any trouble.

To give you some idea on the rationale for pursuing this approach :
This is a third party code segment, and the gen_header.h is a file that 
contains error codes and error strings based on platform specific 
definitions - it's used all over the place. Am trying to prevent adding 
the dependency to *all* source files, but figuring a minimal set is a pain 
in the neck.

It all seems to work too. Just that there seems to be some kind of a loop
being introduced in the VC2005 solution, resulting in a high CPU usage.

Any hints on how to localise the problem would help...

-shishir

> 
> The FOREACH command can help you do this for more than one source in
> target2.
> 
> Note that generating source files is much easier than generating header
> files because you do not need the OBJECT_DEPENDS part.  Usually we use
> CONFIGURE_FILE to produce header files at CMake time with build-specific
> information.  Then you don't need the generation step at all.

Agreed. Dealing with 3rd party code, I'd like to keep the build system
interference
to a minimum in the hope that upgrading will be easier. 

> 
> -Brad
> 


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