[CMake] Custom Commands and Environmnt Settings for PATH and LD_LIBRARY_PATH

[Matthew Woehlke]

On 2014-04-11 05:32, Jörg Kreuzberger wrote:
> [stuff about environment and custom commands]
>
> So it would help to have a possiblity to have a custom command like this:
>
> add_custom_command( OUTPUT <out>
>                      COMMAND ..
>                      COMMAND ..
>                      ENVIRONMENT PATH=$ENV{PATH}
>                      ENVIRONMENT LD_LIBRARY=

I'm pretty sure this is not the first time this sort of thing has come 
up. It would indeed be useful to be able to pass environment values to a 
custom command without having to roll your own wrapper script. However, 
because the command must be run by the build too, I believe a wrapper of 
some sort is unavoidable (though on POSIX platforms, 'env' can possibly 
serve this purpose).

Bonus points for supporting '{PRE,AP}PEND ENVIRONMENT' which would 
automatically use the platform-appropriate PATH separator to 
prepend/append a specified value to an environment variable (omitting 
the separator if the variable is empty).

However, to do this, I think you would need to teach CMake a new command 
mode, e.g.:

   cmake -E env VAR1=VALUE VAR2:=PREPEND_VALUE VAR3+=APPEND_VALUE \
                command args

I think this would be a nice feature to have, though.

-- 
Matthew