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Re: how to include dependencies only if includes changed


From: Allan Odgaard
Subject: Re: how to include dependencies only if includes changed
Date: Tue, 10 Nov 2009 02:12:24 +0100

On 9 Nov 2009, at 19:25, Mark Galeck (CW) wrote:

[...] I am dealing with a code base of over 8 million lines, more than 1000 .c files, each depending on around 500 .h files. The dependencies, all of them, take about 1 minute to "-include", even if you are just rebuilding one .o file.

The time should be relative to number of total .h files (and I guess number of included files).

I have a much smaller project (~200 sources + ~250 headers) but I noticed that the implicit rules of make can really slow things down:

   % time make
   make: Nothing to be done for `all'.
   real 0m0.318s

   % time make -r
   make: Nothing to be done for `all'.
   real 0m0.090s

Don’t know if you rely on the implicit rules, if not, definitely test how much time they eat. If you do use them, you may be able to just copy those you use and disable the rest.





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