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authorMasahiro Yamada <yamada.masahiro@socionext.com>2018-03-19 20:26:08 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2018-03-26 02:01:27 +0900
commitf98fe47ce51dee6d97dd91bbeccdde23f043c754 (patch)
tree9baebcbde886c154d22f51a01a1ca69bd2442660 /lib/zstd
parentf5f336812c233976ad84995110c2266cd94c5cd0 (diff)
kbuild: link $(real-obj-y) instead of $(obj-y) into built-in.a
In Kbuild, Makefiles can add the same object to obj-y multiple times. So, obj-y += foo.o obj-y += foo.o is fine. However, this is not true when the same object is added multiple times via composite objects. For example, obj-y += foo.o bar.o foo-objs := foo-bar-common.o foo-only.o bar-objs := foo-bar-common.o bar-only.o causes build error because two instances of foo-bar-common.o are linked into the vmlinux. Makefiles tend to invent ugly work-around, for example - lib/zstd/Makefile - drivers/net/ethernet/cavium/liquidio/Makefile The technique used in Kbuild to avoid the multiple definition error is to use $(filter $(obj-y), $^). Here, $^ lists the names of all the prerequisites with duplicated names removed. By replacing it with $(filter $(real-obj-y), $^) we can do likewise for composite objects. For built-in objects, we do not need to keep the composite object structure. We can simply expand them, and link $(real-obj-y) to built-in.a. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Diffstat (limited to 'lib/zstd')
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