[PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[Miguel Ojeda]

GNU Make 4.3 changed the behavior of `#` inside commands in commit
c6966b323811 ("[SV 20513] Un-escaped # are not comments in function
invocations"):

    * 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:
        H := \#
        foo := $(shell echo '$H')
      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.

Unlike other commits in the kernel about this issue, such as commit
633174a7046e ("lib/raid6/test/Makefile: Use $(pound) instead of \#
for Make 4.3"), that fixed the issue for newer GNU Makes, in our case
it was the opposite, i.e. we need to fix it for the older ones: someone
building with e.g. 4.2.1 gets the following error:

    scripts/Makefile.compiler:81: *** unterminated call to function 'call': missing ')'.  Stop.

Thus use the existing variable to fix it.

Reported-by: moyi geek
Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/291565/topic/x/near/512001985
Cc: stable@vger.kernel.org
Fixes: e72a076c620f ("kbuild: fix issues with rustc-option")
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 scripts/Makefile.compiler | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 7ed7f92a7daa..f4fcc1eaaeae 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -79,7 +79,7 @@ ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
 # Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage)
 # TODO: remove RUSTC_BOOTSTRAP=1 when we raise the minimum GNU Make version to 4.4
 __rustc-option = $(call try-run,\
-	echo '#![allow(missing_docs)]#![feature(no_core)]#![no_core]' | RUSTC_BOOTSTRAP=1\
+	echo '$(pound)![allow(missing_docs)]$(pound)![feature(no_core)]$(pound)![no_core]' | RUSTC_BOOTSTRAP=1\
 	$(1) --sysroot=/dev/null $(filter-out --sysroot=/dev/null --target=%,$(2)) $(3)\
 	--crate-type=rlib --out-dir=$(TMPOUT) --emit=obj=- - >/dev/null,$(3),$(4))
 

base-commit: a3cd5f507b72c0532c3345b6913557efab34f405
-- 
2.49.0

Re: [PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[Nicolas Schier]

On Mon, Apr 14, 2025 at 07:12:41PM +0200 Miguel Ojeda wrote:
>GNU Make 4.3 changed the behavior of `#` inside commands in commit
>c6966b323811 ("[SV 20513] Un-escaped # are not comments in function
>invocations"):
>
>    * 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:
>        H := \#
>        foo := $(shell echo '$H')
>      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.
>
>Unlike other commits in the kernel about this issue, such as commit
>633174a7046e ("lib/raid6/test/Makefile: Use $(pound) instead of \#
>for Make 4.3"), that fixed the issue for newer GNU Makes, in our case
>it was the opposite, i.e. we need to fix it for the older ones: someone
>building with e.g. 4.2.1 gets the following error:
>
>    scripts/Makefile.compiler:81: *** unterminated call to function 'call': missing ')'.  Stop.
>
>Thus use the existing variable to fix it.
>
>Reported-by: moyi geek
>Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/291565/topic/x/near/512001985
>Cc: stable@vger.kernel.org
>Fixes: e72a076c620f ("kbuild: fix issues with rustc-option")
>Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
>---
> scripts/Makefile.compiler | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
>index 7ed7f92a7daa..f4fcc1eaaeae 100644
>--- a/scripts/Makefile.compiler
>+++ b/scripts/Makefile.compiler
>@@ -79,7 +79,7 @@ ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
> # Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage)
> # TODO: remove RUSTC_BOOTSTRAP=1 when we raise the minimum GNU Make version to 4.4
> __rustc-option = $(call try-run,\
>-	echo '#![allow(missing_docs)]#![feature(no_core)]#![no_core]' | RUSTC_BOOTSTRAP=1\
>+	echo '$(pound)![allow(missing_docs)]$(pound)![feature(no_core)]$(pound)![no_core]' | RUSTC_BOOTSTRAP=1\
> 	$(1) --sysroot=/dev/null $(filter-out --sysroot=/dev/null --target=%,$(2)) $(3)\
> 	--crate-type=rlib --out-dir=$(TMPOUT) --emit=obj=- - >/dev/null,$(3),$(4))
>
>
>base-commit: a3cd5f507b72c0532c3345b6913557efab34f405
>-- 
>2.49.0
>

Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

Re: [PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[Miguel Ojeda]

On Mon, Apr 14, 2025 at 7:13 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> Reported-by: moyi geek

moyi told me it is OK to add the email from Zulip, so:

Reported-by: moyi geek <1441339168@qq.com>

Cheers,
Miguel

Re: [PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[Alice Ryhl]

On Mon, Apr 14, 2025 at 07:12:41PM +0200, Miguel Ojeda wrote:
> GNU Make 4.3 changed the behavior of `#` inside commands in commit
> c6966b323811 ("[SV 20513] Un-escaped # are not comments in function
> invocations"):
> 
>     * 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:
>         H := \#
>         foo := $(shell echo '$H')
>       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.
> 
> Unlike other commits in the kernel about this issue, such as commit
> 633174a7046e ("lib/raid6/test/Makefile: Use $(pound) instead of \#
> for Make 4.3"), that fixed the issue for newer GNU Makes, in our case
> it was the opposite, i.e. we need to fix it for the older ones: someone
> building with e.g. 4.2.1 gets the following error:
> 
>     scripts/Makefile.compiler:81: *** unterminated call to function 'call': missing ')'.  Stop.
> 
> Thus use the existing variable to fix it.
> 
> Reported-by: moyi geek
> Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/291565/topic/x/near/512001985
> Cc: stable@vger.kernel.org
> Fixes: e72a076c620f ("kbuild: fix issues with rustc-option")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH] rust: kbuild: use `pound` to support GNU Make < 4.3

[Miguel Ojeda]

On Mon, Apr 14, 2025 at 7:13 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> Thus use the existing variable to fix it.

Applied to `rust-fixes` -- thanks everyone!

If Kbuild wants to pick it up instead, please let me know and I will drop it.

Cheers,
Miguel