Re: [PATCH 2/1] Kbuild: fix # escaping in .cmd files for future Make
From: Rasmus Villemoes
Date: Thu Apr 05 2018 - 17:43:14 EST
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?