Re: One cause of spurious rebuilds

[Roland McGrath <roland at redhat dot com>]

> A result from the changed mkdep handling.  When math/m_isinf.o is first
> built, there is no .d file for it.  The "m_%.c: sysdeps/foo_%.c" rule
> triggers, and math/m_isinf.c is created as an intermediate dependency. 
> Therefore it's removed when we're done with it.
> 
> During a second time through make, the .d is loaded.  m_isinf.o now
> explicitly depends on m_isinf.c, so it is not an intermediate file; so the
> fact that it is missing can no longer be ignored.  It is built, and this
> time left around.  libm is rebuilt.
> 
> Solution?  I'm not sure; you might think that this would work:
> .INTERMEDIATE: $(foreach s,.c .S l.c l.S f.c f.S,$(calls:s_%=$(objpfx)m_%$s))

What about:

.PRECIOUS: m_%.c m_%.S

?  That ought to prevent the targets of the generated rules from being
intermediate files, so they are never deleted.  I think that's what we
want, so the .d files can be complete and not refer to anything that might
wind up missing.


Thanks,
Roland