linux-kernel - [PATCH] kbuild: use -- separater intead of $(filter-out ...) for cc-cross-prefix

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Date:   Tue,  9 Jul 2019 15:13:00 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kbuild: use -- separater intead of $(filter-out ...) for cc-cross-prefix

arch/mips/Makefile passes prefixes that start with '-' to cc-cross-prefix
when $(tool-archpref) evaluates to the empty string.

They are filtered-out before the $(shell ...) invocation. Otherwise,
'command -v' would be confused.

  $ command -v -linux-gcc
  bash: command: -l: invalid option
  command: usage: command [-pVv] command [arg ...]

Since commit 913ab9780fc0 ("kbuild: use more portable 'command -v' for
cc-cross-prefix"), cc-cross-prefix throws away the stderr output, so
the console is not polluted in any way.

This is not a big deal in practice, but I see a slightly better taste
in adding '--' to teach it that '-linux-gcc' is an argument instead of
a command option.

This will cause extra forking of subshell, but it will not be noticeable
performance regression.

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

 scripts/Kbuild.include | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 222fd1d7d3ae..c62d690c7dcf 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -79,8 +79,8 @@ endef
 # would try to directly execute the shell builtin 'command'. This workaround
 # should be kept for a long time since this issue was fixed only after the
 # GNU Make 4.2.1 release.
-cc-cross-prefix = $(firstword $(foreach c, $(filter-out -%, $(1)), \
-			$(if $(shell command -v $(c)gcc 2>/dev/null), $(c))))
+cc-cross-prefix = $(firstword $(foreach c, $(1), \
+			$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))

 # output directory for tests below
 TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
-- 
2.17.1