[CMake] Parallel build with custom command

[Ruslan Baratov]

On 07-Oct-14 19:14, Bill Hoffman wrote:
> On 10/7/2014 10:26 AM, Ruslan Baratov wrote:
>>
>> I'm expecting 1 message `Script run`, but I have 5 messages. If I modify
>> `generate.cmake` script so it always write the file then everything
>> works fine.
> Ah OK, I see.  Your depend never gets up to date.  If you touch 
> generate.cmake, and the file already exists, then generate.cmake will 
> always be newer than the file.  And it will always try to run it.  So 
> this is expected.
>
Yes, that's why second file always modified. So assume I have a script 
that generates a lot of *.cpp files. I modify script so it only change 
one file, one file modified - one file recompiled. So what I trying to 
do is optimization that can be checked by rule: "if there is at least 
one file from OUTPUT list that is newer then any file from DEPENDS list 
- you don't need to rerun custom command".

So this optimization is not possible (?) custom command must modify all 
the files from OUTPUT list?

Ruslo