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SubjectRe: [PATCH 2/1] Kbuild: fix # escaping in .cmd files for future Make
2018-03-26 8:09 GMT+09:00 Rasmus Villemoes <linux@rasmusvillemoes.dk>:
> 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@rasmusvillemoes.dk>
> ---
> 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
$$,$$$$,$(cmd_$(1)))))



But, I think the following is an even better fix:

make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst
$$,$$$$,$(cmd_$(1)))))



The following 4 test cases produce the same foo.txt,
but insane .cmd file is produced for some case.
Adjusting the number of back-slashes is not a perfect solution.

Replacing # with $(pound) works for all the cases.


[test code 1]
extra-y := foo.txt

quiet_cmd_foo = DEFINE $@
cmd_foo = echo '\#define FOO' >$@

$(obj)/foo.txt: FORCE
$(call if_changed,foo)


[test code 2]
extra-y := foo.txt

quiet_cmd_foo = DEFINE $@
cmd_foo = echo \\\#define FOO >$@

$(obj)/foo.txt: FORCE
$(call if_changed,foo)


[test code3]
extra-y := foo.txt

quiet_cmd_foo = DEFINE $@
cmd_foo = echo '$(pound)define FOO' >$@

$(obj)/foo.txt: FORCE
$(call if_changed,foo)



[test code4]
extra-y := foo.txt

quiet_cmd_foo = DEFINE $@
cmd_foo = echo \$(pound)define FOO >$@

$(obj)/foo.txt: FORCE
$(call if_changed,foo)





| current | \$(pound) | \\$(pound) | $$(pound)
----------------------------------------------------------
test code1 | OK | OK | NG | OK
test code2 | NG | NG | OK | OK
test code3 | OK | OK | NG | OK
test code4 | NG | NG | OK | OK




--
Best Regards
Masahiro Yamada

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