Re: [PATCH 2/1] Kbuild: fix # escaping in .cmd files for future Make
From: Masahiro Yamada
Date: Thu Apr 05 2018 - 23:54:06 EST
2018-04-06 6:43 GMT+09:00 Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>:
> On 2018-03-26 13:48, Masahiro Yamada wrote:
>> 2018-03-26 8:09 GMT+09:00 Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>:
>>> The latest official Make release is 4.2.1 from mid-2016, but the current
>>> git release has this relevant note in the NEWS file:
>>> * WARNING: Backward-incompatibility!
>>> Number signs (#) appearing inside a macro reference or function invocation
>>> no longer introduce comments and should not be escaped with backslashes:
>>> thus a call such as:
>>> foo := $(shell echo '#')
>>> is legal. Previously the number sign needed to be escaped, for example:
>>> foo := $(shell echo '\#')
>>> Now this latter will resolve to "\#". If you want to write makefiles
>>> portable to both versions, assign the number sign to a variable:
>>> C := \#
>>> foo := $(shell echo '$C')
>>> This was claimed to be fixed in 3.81, but wasn't, for some reason.
>>> To detect this change search for 'nocomment' in the .FEATURES variable.
>>> Prepare for whatever future Make release contains that change by fixing
>>> up the .cmd file escaping - without this, make always thinks the command
>>> string has changed and hence rebuilds everything.
>>> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
>>> So the previous patch made everything build, but building again
>>> revealed that this central place very much also needed fixing.
>>> scripts/Kbuild.include | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
>>> index 065324a8046f..7a926e4688f4 100644
>>> --- a/scripts/Kbuild.include
>>> +++ b/scripts/Kbuild.include
>>> @@ -10,6 +10,7 @@ space := $(empty) $(empty)
>>> space_escape := _-_SPACE_-_
>>> right_paren := )
>>> left_paren := (
>>> +pound := \#
>>> # Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
>>> @@ -328,7 +329,7 @@ endif
>>> # (needed for make)
>>> # Replace >'< with >'\''< to be able to enclose the whole string in '...'
>>> # (needed for the shell)
>>> -make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(1)))))
>>> +make-cmd = $(call escsq,$(subst $(pound),\\$(pound),$(subst $$,$$$$,$(cmd_$(1)))))
>> Thanks for the patch, but this changes the behavior.
>> With '#' replaced with $(pound), '\\' does not escape anything,
>> so it is treated as '\\'.
>> The following keeps the current behavior:
>> make-cmd = $(call escsq,$(subst $(pound),\$(pound),$(subst
>> But, I think the following is an even better fix:
>> make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst
> Makefile quoting has never been my strong suit. I actually thought I
> tested my change by looking at some .o.cmd files containing \# before
> and after, but I was fooled by tools/ containing and using their own
> copy of make-cmd - so tools/build/Build.include will also need fixing.
> Yes, writing $(pound) to the .cmd file seems like the safest choice. Do
> you want me to respin or can/will you do the patch(es) yourself?
Can you send v2 please?
I will pick it up shortly.