Messages in this thread |  | | From | "Paul Flinders" <> | Subject | Re: source dependencies cleanup? | Date | Tue, 3 Dec 1996 21:36:09 -0000 |
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> From: Andrew E. Mileski <aem@nic.ott.hookup.net> > > Out of interest why doesn't the kernel use -MD to generate dependancies > > on the fly. > > > > If the answer is that we don't want to be tied to gcc then I would suggest > > that it's already too late for that. > > I _think_ the answer is, GCC is simply too slow. The 'mkdep.c' utility > doesn't have all the baggage of GCC, and is very fast.
Everybody who has replied has confused -MD with -M
-M makes gcc output dependancies to stdout, it needs a separate pass to be made use of and is slow. When I did do dependancies this way I quickly discovered that it's faster to do it in Perl as some people have mentioned.
-MD makes the preprocessor output the dependancies to a separate file during normal compilation. It adds just the amout of time taken to open a file and spit half a K or so to it to the compilation. The need for a separate "make depend" phase goes away and the dependancies can't get out of date.
"make config" seems to result in most things being re-compiled anyway as a result of <linux/config.h> and <linux/autoconf.h> being touched. This could be avoided but only at the expense of splitting the config options into several files.
Regards
Paul.
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