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Kbuild: fix # escaping in .cmd files for future Make
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I tried building using a freshly built Make (4.2.1-69-g8a731d1), but
already the objtool build broke with

orc_dump.c: In function ‘orc_dump’:
orc_dump.c:106:2: error: ‘elf_getshnum’ is deprecated [-Werror=deprecated-declarations]
  if (elf_getshdrnum(elf, &nr_sections)) {

Turns out that with that new Make, the backslash was not removed, so cpp
didn't see a #include directive, grep found nothing, and
-DLIBELF_USE_DEPRECATED was wrongly put in CFLAGS.

Now, that new Make behaviour is documented in their 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.

This also fixes up the two make-cmd instances to replace # with $(pound)
rather than with \#. There might very well be other places that need
similar fixup in preparation for whatever future Make release contains
the above change, but at least this builds an x86_64 defconfig with the
new make.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=197847
Cc: Randy Dunlap <[email protected]>
Signed-off-by: Rasmus Villemoes <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
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Villemoes authored and masahir0y committed Apr 10, 2018
1 parent b41d920 commit 9564a8c
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Showing 4 changed files with 9 additions and 5 deletions.
5 changes: 3 additions & 2 deletions scripts/Kbuild.include
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -322,11 +323,11 @@ endif

# Replace >$< with >$$< to preserve $ when reloading the .cmd file
# (needed for make)
# Replace >#< with >\#< to avoid starting a comment in the .cmd file
# Replace >#< with >$(pound)< to avoid starting a comment in the .cmd file
# (needed for make)
# Replace >'< with >'\''< to be able to enclose the whole string in '...'
# (needed for the shell)
make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(1)))))
make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))))

# Find any prerequisites that is newer than target or that does not exist.
# PHONY targets skipped in both cases.
Expand Down
5 changes: 3 additions & 2 deletions tools/build/Build.include
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
# Convenient variables
comma := ,
squote := '
pound := \#

###
# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
Expand Down Expand Up @@ -43,11 +44,11 @@ echo-cmd = $(if $($(quiet)cmd_$(1)),\
###
# Replace >$< with >$$< to preserve $ when reloading the .cmd file
# (needed for make)
# Replace >#< with >\#< to avoid starting a comment in the .cmd file
# Replace >#< with >$(pound)< to avoid starting a comment in the .cmd file
# (needed for make)
# Replace >'< with >'\''< to be able to enclose the whole string in '...'
# (needed for the shell)
make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(1)))))
make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1)))))

###
# Find any prerequisites that is newer than target or that does not exist.
Expand Down
2 changes: 1 addition & 1 deletion tools/objtool/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ CFLAGS += -Wall -Werror $(WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
LDFLAGS += -lelf $(LIBSUBCMD)

# Allow old libelf to be used:
elfshdr := $(shell echo '\#include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)

AWK = awk
Expand Down
2 changes: 2 additions & 0 deletions tools/scripts/Makefile.include
Original file line number Diff line number Diff line change
Expand Up @@ -120,3 +120,5 @@ ifneq ($(silent),1)
QUIET_UNINST = @printf ' UNINST %s\n' $1;
endif
endif

pound := \#

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