[PATCH v2 4/4] kbuild: remove unnecessary in-subshell execution

Masahiro Yamada
2019-01-17T10:02:44Z

The commands surrounded by ( ) are executed in a subshell, but in
most cases, we do not need to spawn an extra subshell.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v2: None

scripts/Makefile.build | 4 ++--
scripts/Makefile.lib | 21 ++++++++++-----------
scripts/mkcompile_h | 4 ++--
3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9800178..f8e2794 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -312,11 +312,11 @@ $(real-obj-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
#
# These mirror gensymtypes_c and co above, keep them in synch.
cmd_gensymtypes_S = \
- (echo "\#include <linux/kernel.h>" ; \
+ { echo "\#include <linux/kernel.h>" ; \
echo "\#include <asm/asm-prototypes.h>" ; \
$(CPP) $(a_flags) $< | \
grep "\<___EXPORT_SYMBOL\>" | \
- sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ) | \
+ sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \
$(GENKSYMS) $(if $(1), -T $(2)) \
$(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index c6fc295..c0abd9a 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -271,7 +271,7 @@ DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
# Generate an assembly file to wrap the output of the device tree compiler
quiet_cmd_dt_S_dtb= DTB $@
cmd_dt_S_dtb= \
-( \
+{ \
echo '\#include <asm-generic/vmlinux.lds.h>'; \
echo '.section .dtb.init.rodata,"a"'; \
echo '.balign STRUCT_ALIGNMENT'; \
@@ -281,7 +281,7 @@ cmd_dt_S_dtb= \
echo '__dtb_$(subst -,_,$(*F))_end:'; \
echo '.global __dtb_$(subst -,_,$(*F))_end'; \
echo '.balign STRUCT_ALIGNMENT'; \
-) > $@
+} > $@

$(obj)/%.dtb.S: $(obj)/%.dtb FORCE
$(call if_changed,dt_S_dtb)
@@ -335,20 +335,20 @@ printf "%08x\n" $$dec_size | \
)

quiet_cmd_bzip2 = BZIP2 $@
- cmd_bzip2 = (cat $(real-prereqs) | bzip2 -9 && $(size_append)) > $@
+ cmd_bzip2 = { cat $(real-prereqs) | bzip2 -9 && $(size_append); } > $@

# Lzma
# ---------------------------------------------------------------------------

quiet_cmd_lzma = LZMA $@
- cmd_lzma = (cat $(real-prereqs) | lzma -9 && $(size_append)) > $@
+ cmd_lzma = { cat $(real-prereqs) | lzma -9 && $(size_append); } > $@

quiet_cmd_lzo = LZO $@
- cmd_lzo = (cat $(real-prereqs) | lzop -9 && $(size_append)) > $@
+ cmd_lzo = { cat $(real-prereqs) | lzop -9 && $(size_append); } > $@

quiet_cmd_lz4 = LZ4 $@
- cmd_lz4 = (cat $(real-prereqs) | lz4c -l -c1 stdin stdout && \
- $(size_append)) > $@
+ cmd_lz4 = { cat $(real-prereqs) | lz4c -l -c1 stdin stdout && \
+ $(size_append); } > $@

# U-Boot mkimage
# ---------------------------------------------------------------------------
@@ -390,12 +390,11 @@ quiet_cmd_uimage = UIMAGE $@
# big dictionary would increase the memory usage too much in the multi-call
# decompression mode. A BCJ filter isn't used either.
quiet_cmd_xzkern = XZKERN $@
- cmd_xzkern = (cat $(real-prereqs) | \
- sh $(srctree)/scripts/xz_wrap.sh && $(size_append)) > $@
+ cmd_xzkern = { cat $(real-prereqs) | sh $(srctree)/scripts/xz_wrap.sh && \
+ $(size_append); } > $@

quiet_cmd_xzmisc = XZMISC $@
- cmd_xzmisc = (cat $(real-prereqs) | \
- xz --check=crc32 --lzma2=dict=1MiB) > $@
+ cmd_xzmisc = cat $(real-prereqs) | xz --check=crc32 --lzma2=dict=1MiB > $@

# ASM offsets
# ---------------------------------------------------------------------------
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 87f1fc9..2339f86 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -62,7 +62,7 @@ UTS_TRUNCATE="cut -b -$UTS_LEN"

# Generate a temporary compile.h

-( echo /\* This file is auto generated, version $VERSION \*/
+{ echo /\* This file is auto generated, version $VERSION \*/
if [ -n "$CONFIG_FLAGS" ] ; then echo "/* $CONFIG_FLAGS */"; fi

echo \#define UTS_MACHINE \"$ARCH\"
@@ -73,7 +73,7 @@ UTS_TRUNCATE="cut -b -$UTS_LEN"
echo \#define LINUX_COMPILE_HOST \"`echo $LINUX_COMPILE_HOST | $UTS_TRUNCATE`\"

echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | grep ' version ' | sed 's/[[:space:]]*$//'`\"
-) > .tmpcompile
+} > .tmpcompile

# Only replace the real compile.h if the new one is different,
# in order to preserve the timestamp and avoid unnecessary
--
2.7.4