[PATCH] kbuild: Add $(strip ...) before compare make variable with string

[PATCH] kbuild: Add $(strip ...) before compare make variable with string

[Wang Nan]

Some of ifneq in Makefile.build works improperly:

 ifneq ($(a)$(b)$(c),)
 ...
 endif

Because some make vairable contains unintended spaces introduced by:

 a := $(x) $(y)

This commit adds $(strip ...) to some potentially buggy ifneq.

Signed-off-by: Wang Nan <pi3orama@163.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
---
 scripts/Makefile.build | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9fcbfac..b2bc0db 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -46,7 +46,7 @@ include $(kbuild-file)
 include scripts/Makefile.lib
 
 # Do not include host rules unless needed
-ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),)
+ifneq ($(strip $(hostprogs) $(hostcxxlibs-y) $(hostcxxlibs-m)),)
 include scripts/Makefile.host
 endif
 
@@ -55,7 +55,7 @@ $(warning kbuild: Makefile.build is included improperly)
 endif
 
 ifeq ($(need-modorder),)
-ifneq ($(obj-m),)
+ifneq ($(strip $(obj-m)),)
 $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
 $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
 endif
@@ -512,7 +512,7 @@ obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
 # If targets exist, their directories apparently exist. Skip mkdir.
 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
-ifneq ($(obj-dirs),)
+ifneq ($(strip $(obj-dirs)),)
 $(shell mkdir -p $(obj-dirs))
 endif
 endif
-- 
2.7.4

Re: [PATCH] kbuild: Add $(strip ...) before compare make variable with string

[Masahiro Yamada]

On Sat, Apr 25, 2020 at 3:09 PM Wang Nan <pi3orama@163.com> wrote:
>
> Some of ifneq in Makefile.build works improperly:
>
>  ifneq ($(a)$(b)$(c),)
>  ...
>  endif
>
> Because some make vairable contains unintended spaces introduced by:
>
>  a := $(x) $(y)


Right.
I made a mistake in commit 5f2fb52fac15a

$(hostprogs) always contains a space due to this line:

hostprogs  += $(hostprogs-y) $(hostprogs-m)


This line will go away soon, though.



>
> This commit adds $(strip ...) to some potentially buggy ifneq.
>
> Signed-off-by: Wang Nan <pi3orama@163.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Michal Marek <michal.lkml@markovi.net>
> ---
>  scripts/Makefile.build | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 9fcbfac..b2bc0db 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -46,7 +46,7 @@ include $(kbuild-file)
>  include scripts/Makefile.lib
>
>  # Do not include host rules unless needed
> -ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),)
> +ifneq ($(strip $(hostprogs) $(hostcxxlibs-y) $(hostcxxlibs-m)),)

Only this one is correct.


>  include scripts/Makefile.host
>  endif
>
> @@ -55,7 +55,7 @@ $(warning kbuild: Makefile.build is included improperly)
>  endif
>
>  ifeq ($(need-modorder),)
> -ifneq ($(obj-m),)
> +ifneq ($(strip $(obj-m)),)


obj-m           := $(addprefix $(obj)/,$(obj-m))

has always stripped away spaces.



>  $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
>  $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
>  endif
> @@ -512,7 +512,7 @@ obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
>  # If targets exist, their directories apparently exist. Skip mkdir.
>  existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
>  obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
> -ifneq ($(obj-dirs),)


The previous line has $(strip )



> +ifneq ($(strip $(obj-dirs)),)
>  $(shell mkdir -p $(obj-dirs))
>  endif
>  endif
> --
> 2.7.4
>
>


-- 
Best Regards
Masahiro Yamada