[PATCH v2 1/2] kbuild: revive "Entering directory" for Make >= 4.4.1

[Masahiro Yamada]

With commit 9da0763bdd82 ("kbuild: Use relative path when building in
a subdir of the source tree"), compiler messages in out-of-tree builds
include relative paths, which are relative to the build directory, not
the directory where make was started.

To help IDEs/editors find the source files, Kbuild lets GNU Make print
"Entering directory ..." when it changes the working directory. It has
been working fine for a long time, but David reported it is broken with
the latest GNU Make.

The behavior was changed by GNU Make commit 8f9e7722ff0f ("[SV 63537]
Fix setting -w in makefiles"). Previously, setting --no-print-directory
to MAKEFLAGS only affected child makes, but it is now interpreted in
the current make as soon as it is set.

[test code]

  $ cat /tmp/Makefile
  ifneq ($(SUBMAKE),1)
  MAKEFLAGS += --no-print-directory
  all: ; $(MAKE) SUBMAKE=1
  else
  all: ; :
  endif

[before 8f9e7722ff0f]

  $ make -C /tmp
  make: Entering directory '/tmp'
  make SUBMAKE=1
  :
  make: Leaving directory '/tmp'

[after 8f9e7722ff0f]

  $ make -C /tmp
  make SUBMAKE=1
  :

Previously, the effect of --no-print-directory was delayed until Kbuild
started the directory descending, but it is no longer true with GNU Make
4.4.1.

This commit adds one more recursion to cater to GNU Make >= 4.4.1.

When Kbuild needs to change the working directory, __submake will be
executed twice.

  __submake without --no-print-directory  --> show "Entering directory ..."
  __submake with    --no-print-directory  --> parse the rest of Makefile

We end up with one more recursion than needed for GNU Make < 4.4.1, but
I do not want to complicate the version check.

Reported-by: David Howells <dhowells@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/2427604.1686237298@xxxxxxxxxxxxxxxxxxxxxx/
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

Changes in v2:
  - Fix the code. V1 did not work.
  - Remove the version check to simplify the code

 Makefile | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index cc3fe09c4dec..916c1a7984b0 100644
--- a/Makefile
+++ b/Makefile
@@ -189,13 +189,6 @@ else
 abs_objtree := $(CURDIR)
 endif # ifneq ($(KBUILD_OUTPUT),)
 
-ifeq ($(abs_objtree),$(CURDIR))
-# Suppress "Entering directory ..." unless we are changing the work directory.
-MAKEFLAGS += --no-print-directory
-else
-need-sub-make := 1
-endif
-
 this-makefile := $(lastword $(MAKEFILE_LIST))
 abs_srctree := $(realpath $(dir $(this-makefile)))
 
@@ -214,6 +207,23 @@ endif
 export abs_srctree abs_objtree
 export sub_make_done := 1
 
+endif # sub_make_done
+
+ifeq ($(abs_objtree),$(CURDIR))
+# Suppress "Entering directory ..." if we are at the final work directory.
+no-print-directory := --no-print-directory
+else
+# Recursion to show "Entering directory ..."
+need-sub-make := 1
+endif
+
+ifeq ($(filter --no-print-directory, $(MAKEFLAGS)),)
+# If --no-print-directory is unset, recurse once again to set it.
+# You may end up with recursing into __sub-make twice. This is due to the
+# behavior change for GNU Make 4.4.1.
+need-sub-make := 1
+endif
+
 ifeq ($(need-sub-make),1)
 
 PHONY += $(MAKECMDGOALS) __sub-make
@@ -223,18 +233,12 @@ $(filter-out $(this-makefile), $(MAKECMDGOALS)) __all: __sub-make
 
 # Invoke a second make in the output directory, passing relevant variables
 __sub-make:
-	$(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
+	$(Q)$(MAKE) $(no-print-directory) -C $(abs_objtree) \
+	-f $(abs_srctree)/Makefile $(MAKECMDGOALS)
 
-endif # need-sub-make
-endif # sub_make_done
+else # need-sub-make
 
 # We process the rest of the Makefile if this is the final invocation of make
-ifeq ($(need-sub-make),)
-
-# Do not print "Entering directory ...",
-# but we want to display it when entering to the output directory
-# so that IDEs/editors are able to understand relative filenames.
-MAKEFLAGS += --no-print-directory
 
 ifeq ($(abs_srctree),$(abs_objtree))
         # building in the source tree
-- 
2.39.2