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lib/clz_tab.c: put in lib-y rather than obj-y

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The clz table (__clz_tab) in lib/clz_tab.c is also provided as part of
libgcc.a, and many architectures link against libgcc.  To allow the
linker to avoid a multiple-definition link failure, clz_tab.o has to be
in lib/lib.a rather than lib/builtin.o.  The specific issue is that
libgcc.a comes before lib/builtin.o on vmlinux.o's link command line, so
its _clz.o is pulled to satisfy __clz_tab, and then when the remainder
of lib/builtin.o is pulled in to satisfy all the other dependencies, the
__clz_tab symbols conflict.  By putting clz_tab.o in lib.a, the linker
can simply avoid pulling it into vmlinux.o when this situation arises.

The definitions of __clz_tab are the same in libgcc.a and in the kernel;
arguably we could also simply rename the kernel version, but it's
unlikely the libgcc version will ever change to become incompatible, so
just using it seems reasonably safe.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Chris Metcalf 2016-01-20 14:59:12 -08:00 committed by Linus Torvalds
parent 243c2137cd
commit f594870189
1 changed files with 1 additions and 1 deletions
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2
lib/Makefile
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@ -154,7 +154,7 @@ obj-$(CONFIG_GLOB) += glob.o
obj-$(CONFIG_MPILIB) += mpi/
obj-$(CONFIG_SIGNATURE) += digsig.o
obj-$(CONFIG_CLZ_TAB) += clz_tab.o
lib-$(CONFIG_CLZ_TAB) += clz_tab.o
obj-$(CONFIG_DDR) += jedec_ddr_data.o