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

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 [email protected]

Fixes e72a076c620f ("kbuild: fix issues with rustc-option")

Signed-off-by Miguel Ojeda <[email protected]>

---
scripts/Makefile.compiler | 2 +-

1 file changed, 1 insertion(+), 1 deletion(-)

scripts/Makefile.compiler +1 -1

index 7ed7f92a7daa..f4fcc1eaaeae 100644
@@ -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

Signature · 1 line

2.49.0

Reported-by moyi geek

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 [email protected]

Fixes e72a076c620f ("kbuild: fix issues with rustc-option")

Signed-off-by Miguel Ojeda <[email protected]>

Thus use the existing variable to fix it.