linux/arch/arc
Masahiro Yamada 54a702f705 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>
2018-04-07 19:04:02 +09:00
..
boot kbuild: mark $(targets) as .SECONDARY and remove .PRECIOUS markers 2018-04-07 19:04:02 +09:00
configs Driver Core updates for 4.16-rc1 2018-02-01 10:00:28 -08:00
include ARC fixes for 4.16-rc4 2018-03-01 14:32:23 -08:00
kernel Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-04-06 11:07:08 -07:00
lib
mm mm: fix races between swapoff and flush dcache 2018-04-05 21:36:26 -07:00
oprofile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
plat-axs10x ARC: [plat-axs103] refactor the quad core DT quirk code 2017-12-20 12:41:45 -08:00
plat-eznps License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
plat-hsdk ARC: [plat-hsdk]: Get rid of core pll frequency set in platform code 2017-12-20 12:41:44 -08:00
plat-sim ARC: [plat-sim] Include this platform unconditionally 2017-08-04 13:49:47 +05:30
plat-tb10x
Kbuild
Kconfig ARC fixes for 4.16-rc4 2018-03-01 14:32:23 -08:00
Kconfig.debug License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile arc: remove redundant UTS_MACHINE define in arch/arc/Makefile 2017-10-03 20:36:49 -07:00