Re: How to modify algorithm that determines weather a target needs rebuild

[Paul Smith]

On Mon, 2010-08-09 at 22:06 -0700, mirage1987 wrote:
> I have my codebase residing on clearcase. Since i am using a dynamic view
> the MVFS provides me with files based on the timestamp at which they were
> last checked in.

Ah HAH!  I knew you were using ClearCase :-).

> The two obvious solutions to this would be to
> - either use clearcase make [has drawbacks.. doesn't involve all gnu make
> features]

Nevertheless, this is the right answer.  If you need more GNU make
features, file bugs with ClearCase development.

> - First timestamps can't be very reliable while matching for equality[ i aim
> to have the equality with +- delta]

This isn't a problem with ClearCase because MVFS doesn't (or at least
didn't last I used it) support sub-second timestamps, and you don't have
to worry about different types of filesystems with different timestamp
behaviors: they're all MVFS and work the same way.

> - Another is "How to i handle multiple dependencies with equality"
>    That is one question that perhaps presents a roadblock to the equality
> approach.. I can't think of any solution to overcome that.

Indeed.

> But i am thinking of an alternate approach:
> - With each <target-dependencies> rule i'll do the following 
> See if timestamp of any of the dependencies has changed. If yes build.
> I can do this by either storing the older timestamps <may be their sum/
> checksum of timestamps> in an external file [as pointed by TODD] and
> comparing them with the present
> And check for equality ( may be +- delta if i go for the sum)
> 
> I can't figure out the way to solve the 'X' part of the problem [may be you
> guys can suggest better] so i resorted to solving the 'Y' part.

Solving the X part is going back to using clearmake.

> Please let me know in case what i talked above is feasible without much
> affecting the performance or complexity of the "make" process. Or any
> alternate solution could help.

This is not a simple change, at all.  It will require very significant
effort.  But there's no alternate solution because you cannot change the
way ClearCase works.

As I said before that's why ClearCase, pretty much alone of all source
code control tools, provides its own build utility.

Plus if you use clearmake you can get winkin, which is pretty neat
actually.

-- 
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 Paul D. Smith <address@hidden>          Find some GNU make tips at:
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