[Bug bootstrap/17817] [4.0 Regression] restage[1,2,3] and then bootstrap no longer cause build dir to be rebuilt

["kcook at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From kcook at gcc dot gnu dot org  2004-10-04 16:54 -------
Subject: Re:  [4.0 Regression] restage[1,2,3] and then bootstrap no longer cause build dir to be rebuilt

I believe that this is currently working as intended.

The files in build/* are only built by the build compiler and do not
get rebuilt between stages unless one of its dependendent source files
changed.  The idea was to speed up bootstraps by not requiring the
generator programs, some of which on some (*cough* darwin) platforms
take a half hour to run, to be needlessly rerun multiple times only to
produce identical output.  For a long winded explanation, see
http://gcc.gnu.org/ml/gcc-patches/2004-09/msg00091.html.

In current CVS, the generator programs are no longer being rebuilt, yet
they are still being rerun.  I have an, as yet unsubmitted, three line
patch which would change the latter behavior to no longer erase the
stamp files between stages for the generated files such as
insn-attrtab.c.  I've been piecemealing the changes in, waiting a week
or two for some negative feedback from the each piece, which you have
now provided.

Do you have a specific example where the new behaviour you have noticed
is causing a problem?

If there is a real problem with this, then restoring previous behavior
of rebuilding the gen* programs each time would be a simple change:
either a one-liner to also stage bconfig.h or with some slightly more
complication properly stage the entire build directory.

Though I may be overlooking something, I'm under the impression that
the benefits of a significantly quicker bootstrap will outweigh the
risks of a missing a hypothetical bug in the stage2 compiler which
causes a problem while generating our generated *.c files, yet not
causing a bootstrap miscompare nor a problem overlooked by the
testsuite.

Also it is noteworthy that none of the behavior you are seeing will
occur with the Paolo's top level bootstrap which I was under the
impression was supposed to become the default RSN.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17817