[cmake-developers] INCLUDE_DIRECTORIES variable expansion (was: Performance problem in tll-set-include-and-defines-requirements)

[David Cole]

Before we do another policy here, does the performance problem go away if
you comment out the SetProperty calls?

If so, we can just add some code that detects whether any variables were
actually expanded in the call, and then only call SetProperty when that's
the case. (In the vast majority of cases there will not be any variables in
the property values...)

The code is left in there simply because it was there before the "moving
includes to a target property" change.

It is still unclear to me why that code is required. I suspect it is
probably not at this point, but since I don't understand the full history
there, I can't state that with 100% certainty.

This is a problem only now that generator expressions are use-able in this
context. If there were no $ in the input, then ExpandVariablesInString
would return immediately without doing any significant work...




On Thu, Nov 29, 2012 at 2:30 PM, David Cole <david.cole at kitware.com> wrote:

> Looking at this now, will reply in just a minute
>
>
>
>
> On Thu, Nov 29, 2012 at 2:14 PM, Stephen Kelly <steveire at gmail.com> wrote:
>
>> Brad King wrote:
>>
>> > On 11/29/2012 07:34 AM, Stephen Kelly wrote:
>> >> The patch that added that line is
>> >> d899eb71b52616c9e3f3f5987f229619605e632b. It is apparently there for
>> >> strict backwards compatibility, but it is not clear what exactly needs
>> to
>> >> be backwards compatible there. Any idea about that?
>> >
>> > I don't know off the top of my head, Dave?
>> >
>> > Stephen, please add the policy that the d899eb71 commit message
>> > suggests.  Only bother with expansion if the policy is OLD or
>> > not set.
>>
>> Ok, I'll wait until we hear from Dave so I can write a well-informed
>> commit
>> message.
>>
>> Thanks,
>>
>> Steve.
>>
>>
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