linux-kernel - [PATCH 2/2] kbuild: sort hostprogs before passing it to ifneq

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Date:   Wed, 29 Jul 2020 12:15:37 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] kbuild: sort hostprogs before passing it to ifneq

The conditional:

  ifneq ($(hostprogs),)

... is evaluated to true if $(hostprogs) does not contain any word but
whitespace characters.

  ifneq ($(strip $(hostprogs)),)

... is a safe way to avoid interpreting whitespace as a non-empty value,
but I'd rather want to use the side-effect of $(sort ...) to do the
equivalent.

$(sort ...) is used in scripts/Makefile.host in order to drop duplication
in $(hostprogs). It is also useful to strip excessive spaces.

Move $(sort ...) before evaluating the ifneq.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/Makefile.build |  5 ++++-
 scripts/Makefile.host  | 10 ++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index d41c1cd453b9..e0b6b5db11c2 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -45,12 +45,15 @@ include $(kbuild-file)
 
 include scripts/Makefile.lib
 
-# Do not include hostprogs rules unless needed
+# Do not include hostprogs rules unless needed.
+# $(sort ...) is used here to remove duplicated words and excessive spaces.
+hostprogs := $(sort $(hostprogs))
 ifneq ($(hostprogs),)
 include scripts/Makefile.host
 endif
 
 # Do not include userprogs rules unless needed.
+# $(sort ...) is used here to remove duplicated words and excessive spaces.
 userprogs := $(sort $(userprogs))
 ifneq ($(userprogs),)
 include scripts/Makefile.userprogs
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index 687ca3f309e9..278b4d6ac945 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -38,24 +38,22 @@ $(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
 # Will compile qconf as a C++ program, and menu as a C program.
 # They are linked as C++ code to the executable qconf
 
-__hostprogs := $(sort $(hostprogs))
-
 # C code
 # Executables compiled from a single .c file
-host-csingle	:= $(foreach m,$(__hostprogs), \
+host-csingle	:= $(foreach m,$(hostprogs), \
 			$(if $($(m)-objs)$($(m)-cxxobjs),,$(m)))
 
 # C executables linked based on several .o files
-host-cmulti	:= $(foreach m,$(__hostprogs),\
+host-cmulti	:= $(foreach m,$(hostprogs),\
 		   $(if $($(m)-cxxobjs),,$(if $($(m)-objs),$(m))))
 
 # Object (.o) files compiled from .c files
-host-cobjs	:= $(sort $(foreach m,$(__hostprogs),$($(m)-objs)))
+host-cobjs	:= $(sort $(foreach m,$(hostprogs),$($(m)-objs)))
 
 # C++ code
 # C++ executables compiled from at least one .cc file
 # and zero or more .c files
-host-cxxmulti	:= $(foreach m,$(__hostprogs),$(if $($(m)-cxxobjs),$(m)))
+host-cxxmulti	:= $(foreach m,$(hostprogs),$(if $($(m)-cxxobjs),$(m)))
 
 # C++ Object (.o) files compiled from .cc files
 host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
-- 
2.25.1