[1/2] Kbuild: fix # escaping in .cmd files for future Make

Message ID 1537324557-27033-2-git-send-email-yamada.masahiro@socionext.com
State New
Headers show
Series
  • Fix build with the latest GNU Make
Related show

Commit Message

Masahiro Yamada Sept. 19, 2018, 2:35 a.m.
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

[ commit 9564a8cf422d7b58f6e857e3546d346fa970191e in Linux ]

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 <rdunlap@infradead.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 scripts/Kbuild.include | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

Tom Rini Sept. 30, 2018, 7:25 p.m. | #1
On Wed, Sep 19, 2018 at 11:35:56AM +0900, Masahiro Yamada wrote:

> From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

> 

> [ commit 9564a8cf422d7b58f6e857e3546d346fa970191e in Linux ]

> 

> 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 <rdunlap@infradead.org>

> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>


Applied to u-boot/master, thanks!

-- 
Tom

Patch

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 2c7918a..13ebddd 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -7,6 +7,7 @@  quote   := "
 squote  := '
 empty   :=
 space   := $(empty) $(empty)
+pound := \#
 
 ###
 # Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
@@ -242,11 +243,11 @@  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.