[PATCH RFC next 08/18] scripts/Makefile.extrawarn: sync with 6.1

Mon May 4 15:20:35 CEST 2026

From: Quentin Schulz <quentin.schulz at cherry.de>

Sync scripts/Makefile.extrawarn with Linux kernel 6.1's.

Since it adds a new option for KBUILD_EXTRA_WARN with e, document it as
done in kernel commit c77d06e70d59 ("kbuild: support W=e to make build
abort in case of warning").

s/gcc/build/ in Makefile as done in kernel commit e27128db6283 ("kbuild:
rename KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARN"), part of
v5.4. The rest of this commit was backported with commit bd3f9ee679b4
("kbuild: Bump the build system to 6.1").

Our scripts/Makefile.extrawarn before this commit is Linux kernel's from
v5.1 with the following diff:

 # diff --git a/proc/self/fd/11 b/proc/self/fd/13
 # --- a/proc/self/fd/11
 # +++ b/proc/self/fd/13
 # @@ -13,17 +13,8 @@
 #
 #  KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 #
 # -# backward compatibility
 # -KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
 # -
 #  ifeq ("$(origin W)", "command line")
 # -  KBUILD_EXTRA_WARN := $(W)
 # -endif
 # -
 # -export KBUILD_EXTRA_WARN
 # -
 # -ifeq ("$(origin W)", "command line")
 # -  KBUILD_EXTRA_WARN := $(W)
 # +  export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
 #  endif
 #
 #  ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS

The KBUILD_EXTRA_WARN changes were made as part of commit bd3f9ee679b4
("kbuild: Bump the build system to 6.1") and they are available in v5.4
via kernel commit e27128db6283 ("kbuild: rename
KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARN") so they are pulled
in this sync. Additional changes made in other files are either ignored
because the files or modified code parts don't exist. The change made to
the Makefile is included in this commit here.

scripts/Makefile.extrawarn is now directly copied from Linux kernel at
v6.1, no changes made.

Signed-off-by: Quentin Schulz <quentin.schulz at cherry.de>
---
 Makefile                   |   3 +-
 scripts/Makefile.extrawarn | 152 +++++++++++++++++++++++++++------------------
 2 files changed, 94 insertions(+), 61 deletions(-)

diff --git a/Makefile b/Makefile
index bfd4976a0d4..aed54cee4a4 100644
--- a/Makefile
+++ b/Makefile
@@ -2741,10 +2741,11 @@ help:
 	@echo  '  make C=1   [targets] Check all c source with $$CHECK (sparse by default)'
 	@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'
 	@echo  '  make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
-	@echo  '  make W=n   [targets] Enable extra gcc checks, n=1,2,3 where'
+	@echo  '  make W=n   [targets] Enable extra build checks, n=1,2,3 where'
 	@echo  '		1: warnings which may be relevant and do not occur too often'
 	@echo  '		2: warnings which occur quite often but may still be relevant'
 	@echo  '		3: more obscure warnings, can most likely be ignored'
+	@echo  '		e: warnings are being treated as errors'
 	@echo  '		Multiple levels can be combined with W=12 or W=123'
 	@echo  ''
 	@echo  'Execute "make" or "make all" to build all targets marked with [*] '
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 7dfc374a19d..6bbba36c596 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -1,14 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 # ==========================================================================
-#
 # make W=... settings
 #
-# W=1 - warnings that may be relevant and does not occur too often
-# W=2 - warnings that occur quite often but may still be relevant
-# W=3 - the more obscure warnings, can most likely be ignored
-#
-# $(call cc-option, -W...) handles gcc -W.. options which
-# are not supported by all versions of the compiler
+# There are four warning groups enabled by W=1, W=2, W=3, and W=e
+# They are independent, and can be combined like W=12 or W=123e.
 # ==========================================================================
 
 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
@@ -22,64 +17,101 @@ endif
 
 export KBUILD_EXTRA_WARN
 
-ifeq ("$(origin W)", "command line")
-  KBUILD_EXTRA_WARN := $(W)
-endif
+#
+# W=1 - warnings which may be relevant and do not occur too often
+#
+ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
 
-ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS
-warning-  := $(empty)
+KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
+KBUILD_CFLAGS += -Wmissing-declarations
+KBUILD_CFLAGS += -Wmissing-format-attribute
+KBUILD_CFLAGS += -Wmissing-prototypes
+KBUILD_CFLAGS += -Wold-style-definition
+KBUILD_CFLAGS += -Wmissing-include-dirs
+KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
+KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
+KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
+KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
+# The following turn off the warnings enabled by -Wextra
+KBUILD_CFLAGS += -Wno-missing-field-initializers
+KBUILD_CFLAGS += -Wno-sign-compare
+KBUILD_CFLAGS += -Wno-type-limits
+KBUILD_CFLAGS += -Wno-shift-negative-value
 
-warning-1 := -Wextra -Wunused -Wno-unused-parameter
-warning-1 += -Wmissing-declarations
-warning-1 += -Wmissing-format-attribute
-warning-1 += $(call cc-option, -Wmissing-prototypes)
-warning-1 += -Wold-style-definition
-warning-1 += $(call cc-option, -Wmissing-include-dirs)
-warning-1 += $(call cc-option, -Wunused-but-set-variable)
-warning-1 += $(call cc-option, -Wunused-const-variable)
-warning-1 += $(call cc-option, -Wpacked-not-aligned)
-warning-1 += $(call cc-option, -Wstringop-truncation)
-warning-1 += $(call cc-disable-warning, missing-field-initializers)
-warning-1 += $(call cc-disable-warning, sign-compare)
+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 
-warning-2 := -Waggregate-return
-warning-2 += -Wcast-align
-warning-2 += -Wdisabled-optimization
-warning-2 += -Wnested-externs
-warning-2 += -Wshadow
-warning-2 += $(call cc-option, -Wlogical-op)
-warning-2 += $(call cc-option, -Wmissing-field-initializers)
-warning-2 += $(call cc-option, -Wsign-compare)
-warning-2 += $(call cc-option, -Wmaybe-uninitialized)
-warning-2 += $(call cc-option, -Wunused-macros)
-
-warning-3 := -Wbad-function-cast
-warning-3 += -Wcast-qual
-warning-3 += -Wconversion
-warning-3 += -Wpacked
-warning-3 += -Wpadded
-warning-3 += -Wpointer-arith
-warning-3 += -Wredundant-decls
-warning-3 += -Wswitch-default
-warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
-
-warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-
-ifeq ("$(strip $(warning))","")
-        $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
-endif
-
-KBUILD_CFLAGS += $(warning)
 else
 
+# Some diagnostics enabled by default are noisy.
+# Suppress them by using -Wno... except for W=1.
+
 ifdef CONFIG_CC_IS_CLANG
-KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
-KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)
-KBUILD_CFLAGS += $(call cc-disable-warning, format)
-KBUILD_CFLAGS += $(call cc-disable-warning, sign-compare)
-KBUILD_CFLAGS += $(call cc-disable-warning, format-zero-length)
-KBUILD_CFLAGS += $(call cc-disable-warning, uninitialized)
+KBUILD_CFLAGS += -Wno-initializer-overrides
+# Clang before clang-16 would warn on default argument promotions.
+ifneq ($(call clang-min-version, 160000),y)
+# Disable -Wformat
+KBUILD_CFLAGS += -Wno-format
+# Then re-enable flags that were part of the -Wformat group that aren't
+# problematic.
+KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
+KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
+# Requires clang-12+.
+ifeq ($(call clang-min-version, 120000),y)
+KBUILD_CFLAGS += -Wformat-insufficient-args
 endif
 endif
+KBUILD_CFLAGS += -Wno-sign-compare
+KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
+KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
+KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
+KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
+endif
+
+endif
+
+#
+# W=2 - warnings which occur quite often but may still be relevant
+#
+ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
+
+KBUILD_CFLAGS += -Wdisabled-optimization
+KBUILD_CFLAGS += -Wshadow
+KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
+KBUILD_CFLAGS += -Wmissing-field-initializers
+KBUILD_CFLAGS += -Wtype-limits
+KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
+KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
+
+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
+
+endif
+
+#
+# W=3 - more obscure warnings, can most likely be ignored
+#
+ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
+
+KBUILD_CFLAGS += -Wbad-function-cast
+KBUILD_CFLAGS += -Wcast-align
+KBUILD_CFLAGS += -Wcast-qual
+KBUILD_CFLAGS += -Wconversion
+KBUILD_CFLAGS += -Wpacked
+KBUILD_CFLAGS += -Wpadded
+KBUILD_CFLAGS += -Wpointer-arith
+KBUILD_CFLAGS += -Wredundant-decls
+KBUILD_CFLAGS += -Wsign-compare
+KBUILD_CFLAGS += -Wswitch-default
+KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
+
+KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
+
+endif
+
+#
+# W=e - error out on warnings
+#
+ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
+
+KBUILD_CFLAGS += -Werror
+
+endif

-- 
2.54.0

