kbuild: mark $(targets) as .SECONDARY and remove .PRECIOUS markers

GNU Make automatically deletes intermediate files that are updated
in a chain of pattern rules.

Example 1) %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
Example 2) %.o <- %.c <- %.c_shipped

A couple of makefiles mark such targets as .PRECIOUS to prevent Make
from deleting them, but the correct way is to use .SECONDARY.

  .SECONDARY
    Prerequisites of this special target are treated as intermediate
    files but are never automatically deleted.

  .PRECIOUS
    When make is interrupted during execution, it may delete the target
    file it is updating if the file was modified since make started.
    If you mark the file as precious, make will never delete the file
    if interrupted.

Both can avoid deletion of intermediate files, but the difference is
the behavior when Make is interrupted; .SECONDARY deletes the target,
but .PRECIOUS does not.

The use of .PRECIOUS is relatively rare since we do not want to keep
partially constructed (possibly corrupted) targets.

Another difference is that .PRECIOUS works with pattern rules whereas
.SECONDARY does not.

  .PRECIOUS: $(obj)/%.lex.c

works, but

  .SECONDARY: $(obj)/%.lex.c

has no effect.  However, for the reason above, I do not want to use
.PRECIOUS which could cause obscure build breakage.

The targets specified as .SECONDARY must be explicit.  $(targets)
contains all targets that need to include .*.cmd files.  So, the
intermediates you want to keep are mostly in there.  Therefore, mark
$(targets) as .SECONDARY.  It means primary targets are also marked
as .SECONDARY, but I do not see any drawback for this.

I replaced some .SECONDARY / .PRECIOUS markers with 'targets'.  This
will make Kbuild search for non-existing .*.cmd files, but this is
not a noticeable performance issue.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Frank Rowand <frowand.list@gmail.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Masahiro Yamada 2018-03-23 22:04:39 +09:00
parent 4fa8bc949d
commit 54a702f705
8 changed files with 11 additions and 20 deletions

View File

@ -9,8 +9,6 @@ endif
obj-y += $(builtindtb-y).dtb.o
dtb-y := $(builtindtb-y).dtb
.SECONDARY: $(obj)/$(builtindtb-y).dtb.S
# for CONFIG_OF_ALL_DTBS test
dtstree := $(srctree)/$(src)
dtb- := $(patsubst $(dtstree)/%.dts,%.dtb, $(wildcard $(dtstree)/*.dts))

View File

@ -67,4 +67,4 @@ $(src)/sha512-core.S_shipped: $(src)/sha512-armv4.pl
$(call cmd,perl)
endif
.PRECIOUS: $(obj)/sha256-core.S $(obj)/sha512-core.S
targets += sha256-core.S sha512-core.S

View File

@ -78,4 +78,4 @@ $(src)/sha512-core.S_shipped: $(src)/sha512-armv8.pl
$(call cmd,perlasm)
endif
.PRECIOUS: $(obj)/sha256-core.S $(obj)/sha512-core.S
targets += sha256-core.S sha512-core.S

View File

@ -29,9 +29,7 @@ vdso_img_cfiles := $(vdso_img-y:%=vdso-image-%.c)
vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg)
obj-y += $(vdso_img_objs)
targets += $(vdso_img_cfiles)
targets += $(vdso_img_sodbg)
.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c) \
$(vdso_img-y:%=$(obj)/vdso%.so)
targets += $(vdso_img_sodbg) $(vdso_img-y:%=vdso%.so)
export CPPFLAGS_vdso.lds += -P -C

View File

@ -42,9 +42,7 @@ vdso_img_cfiles := $(vdso_img-y:%=vdso-image-%.c)
vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg)
obj-y += $(vdso_img_objs)
targets += $(vdso_img_cfiles)
targets += $(vdso_img_sodbg)
.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c) \
$(vdso_img-y:%=$(obj)/vdso%.so)
targets += $(vdso_img_sodbg) $(vdso_img-y:%=vdso%.so)
export CPPFLAGS_vdso.lds += -P -C

View File

@ -30,7 +30,3 @@ DTC_FLAGS_testcases += -@
# suppress warnings about intentional errors
DTC_FLAGS_testcases += -Wno-interrupts_property
.PRECIOUS: \
$(obj)/%.dtb.S \
$(obj)/%.dtb

View File

@ -430,8 +430,6 @@ quiet_cmd_asn1_compiler = ASN.1 $@
cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
$(subst .h,.c,$@) $(subst .c,.h,$@)
.PRECIOUS: $(objtree)/$(obj)/%.asn1.c $(objtree)/$(obj)/%.asn1.h
$(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
$(call cmd,asn1_compiler)
@ -544,10 +542,12 @@ targets := $(filter-out $(PHONY), $(targets))
intermediate_targets = $(foreach sfx, $(2), \
$(patsubst %$(strip $(1)),%$(sfx), \
$(filter %$(strip $(1)), $(targets))))
# %.asn1.o <- %.asn1.[ch] <- %.asn1
# %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
# %.lex.o <- %.lex.c <- %.l
# %.tab.o <- %.tab.[ch] <- %.y
targets += $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
$(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
$(call intermediate_targets, .lex.o, .lex.c) \
$(call intermediate_targets, .tab.o, .tab.c .tab.h)
@ -587,6 +587,10 @@ $(shell mkdir -p $(obj-dirs))
endif
endif
# Some files contained in $(targets) are intermediate artifacts.
# We never want them to be removed automatically.
.SECONDARY: $(targets)
# Declare the contents of the .PHONY variable as phony. We keep that
# information in a variable se we can use it in if_changed and friends.

View File

@ -184,7 +184,6 @@ endef
quiet_cmd_flex = LEX $@
cmd_flex = $(LEX) -o$@ -L $<
.PRECIOUS: $(obj)/%.lex.c
$(obj)/%.lex.c: $(src)/%.l FORCE
$(call if_changed,flex)
@ -193,14 +192,12 @@ $(obj)/%.lex.c: $(src)/%.l FORCE
quiet_cmd_bison = YACC $@
cmd_bison = $(YACC) -o$@ -t -l $<
.PRECIOUS: $(obj)/%.tab.c
$(obj)/%.tab.c: $(src)/%.y FORCE
$(call if_changed,bison)
quiet_cmd_bison_h = YACC $@
cmd_bison_h = bison -o/dev/null --defines=$@ -t -l $<
.PRECIOUS: $(obj)/%.tab.h
$(obj)/%.tab.h: $(src)/%.y FORCE
$(call if_changed,bison_h)