[CMake] Dependency for launching an application

[Nick Overdijk]

I'm probably missing something, but why

> add_dependencies(parent child)

? That doesn't make sense. Parent is not using anything from child. You can just leave that line away and everything will be fine right?

On 2013-08-02, at 16:24:21 , Andreas Haferburg wrote:

> Yes, that's pretty much the setup we have: The common (static) library contains almost all obj's, and the two exe projects only have a small main.obj and link against the library. I'd like to eliminate the build(=link) time of child.exe by having the linker link both exes at the same time.
> 
> Regards,
> Andreas
> 
> 
> On 08.02.2013 15:41, Patrick Johnmeyer wrote:
>> On Fri, Feb 8, 2013 at 8:16 AM, Andreas Haferburg <ahaferburg at scopis.com
>> <mailto:ahaferburg at scopis.com>> wrote:
>> 
>>    What happens is that common is built, then child, then parent, then parent is executed.
>>    What I'd like to happen is that common is built, then child+parent are being built concurrently,
>>    and as soon as both are done, parent is executed.
>> 
>> 
>> Unfortunately that's just not how dependencies work. If parent is dependent on child, then child
>> will build before parent in serial. And since they are both dependent on common, you essentially
>> have a linear dependency in your example.
>> 
>> You could break this up by creating a new target that is dependent on child and parent, and
>> eliminate parent's direct dependency on child. This will allow child and parent to be built
>> simultaneously. You would then need to "do something" with this new target so that it will cause
>> "parent" to be run.
>> 
>> You may be able to improve build times (assuming that is the driver) by invoking the compiler flag
>> for parallel compilation. Another option may be to convert the majority of child and parent to
>> another library, with small simple executable projects that invoke those libraries. This moves the
>> dependencies around in a way that you *may* get better build performance ... but everything I say is
>> speculative without knowing the nitty gritty of your project -- build times per project, full
>> dependency graph, etc.
> --
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