[CMake] cmake-gui's separation between configuration & generation

[Robert Dailey]

On Thu, Aug 23, 2012 at 10:48 AM, Robert Dailey
<rcdailey.lists at gmail.com> wrote:
> On Thu, Aug 23, 2012 at 10:43 AM, John Drescher <drescherjm at gmail.com> wrote:
>>> Is the separation between configuration & generation really necessary
>>> for cmake-gui? I ask because several of my co-workers are confused
>>> between the differences in the two, even though I explain it.
>>>
>>> Honestly there isn't really a reason that I can think of to do a
>>> configure without a generate, unless you're testing the integrity of
>>> your CMake script changes maybe, but even then, if its broken
>>> generation won't take place.
>>>
>>> The command line program does not separate the two, so I simply think
>>> cmake-gui should eliminate the configure button, and simply have a
>>> generate button. Does this seem fair? Is there a reason why they are
>>> separated?
>>
>> I can think of one use case that I use that the separation is a good
>> thing. What about when you have options and variables that are
>> conditional depending on other CMake variables so that setting the
>> variables / options may take more than 1 configure.
>
> Well, think of this from the perspective of Linux users. They don't
> get to configure seperately, so only Windows users get special
> treatment here (and maybe Mac too, since it's using Qt). Basically, if
> two configures are necessary, you simply just hit the "generate"
> button twice, and the wait may be slightly longer because of the
> generation. However, usually it's the configure step that takes 99% of
> the time and generation is quick since it's just spitting out files to
> disk it seems.
>
> I would also argue that any CMake project should have appropriate
> defaults OR logic to calculate the defaults for you, so that even if a
> user decides to not modify any cache variables, generation should
> always succeed. CMake can't assume that 2 passes will be necessary
> (and it really shouldn't).

Oh and also, if two configures are necessary (say that, a library or
package can't be found intelligently), then the configuration step
would fail and be interrupted, so you get a chance to correct any
errors and adjust appropriate cache variables. So, in this case it
doesn't really matter if you've hit configure or generate.