[CMake] Dependencies when using macro as include filename

[Michael Wild]

On 09/16/2011 01:29 PM, Max Vasin wrote:
> Hello,
> I have a number of headers (say A.h, B.h, C.h) that define some kind
> of hardware abstraction layer, which header to use is determined
> by the CMakeLists.txt and specified by the macro in config.h:
> 
> config.h:
> #cmakedefine HAL_H ${HAL_H}
> 
> The config.h and the HAL_H are included by the header (say P.h).
> 
> P.h:
> #include "config.h"
> #include HAL_H
> 
> When I modify the HAL_H only the program is not rebuilt. I do not what
> to make condition includes like
> 
> P.h:
> #if NEED_A_H
> #  include "A.h"
> #elseif NEED_B_H
> #  include "B.h"
> // etc.
> 
> because I what to have all these condition in CMakeLists.txt only and
> keep P.h simple and straightforward.
> I understand that I can generate P.h with CONFIGURE_FILE but I wonder
> if there are other solutions and which
> solution the community recommends.
> 


The problem is your config.h file. #cmakedefine doesn't do what you
want. What it does is substitute either

#define HAL_H

if the variable HAL_H evaluates to a TRUE value, otherwise to

/* #define HAL_H */

What you want is

#define HAL_H ${HAL_H}

or IMHO preferably

#define HAL_H @HAL_H@

and then use configure_file(... @ONLY).

HTH

Michael