Silent failure when missing bc

Commit Message

Sam Ravnborg May 2, 2013, 8:25 p.m. UTC

On Thu, May 02, 2013 at 04:44:03PM +0200, Ian Kumlien wrote:
> Hi, 
> 
> A dependency on bc was added at some point during the 3.9 development.
> 
> My machines runs a git forest which contains both stable and Torvalds
> mainline. So any kernel version is only a:
> 	git fetch --all && git checkout <tag> away
> 
> When switching from v3.8.5 to v3.9-rc7 i ran in to a odd thing.
> 
> It seemed to build fine, make install and modules_install was all fine
> as well but rebooting revealed that 3.8.5 had been installed again
> instead.
> 
> Doing make clean and rebuilding revealed that I was missing bc ;)
> 
> I have tried to find exactly where it's run since then, i have found the
> cmd_bc section but not found what triggers it... Due to lack of time and
> energy, I hearby report this bug!
> 
> This is about as far as i got:
> kernel/Makefile:135:quiet_cmd_bc  = BC      $@
> kernel/Makefile:136:      cmd_bc  = bc -q $(filter-out FORCE,$^) > $@

Could you try this patch. Untested but I think it required to catch this bug.


> 
> Is there any detaled information and or instructions on kbuild btw?
There is some docs in Documentation/kbuild/* - but I dunno if this is
what you are after.

	Sam
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Patch

diff --git a/kernel/Makefile b/kernel/Makefile
index d1574d4..18a9083 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -134,7 +134,7 @@  $(obj)/hz.bc: $(objtree)/include/config/hz.h FORCE
 	$(call if_changed,hzfile)
 
 quiet_cmd_bc  = BC      $@
-      cmd_bc  = bc -q $(filter-out FORCE,$^) > $@
+      cmd_bc  = bc -q $(filter-out FORCE,$^) > $@ || (rm -f $@; false)
 
 targets += timeconst.h
 $(obj)/timeconst.h: $(obj)/hz.bc $(src)/timeconst.bc FORCE