Merge tag 'kbuild-gnu11-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild update for C11 language base from Masahiro Yamada:
 "Kbuild -std=gnu11 updates for v5.18

  Linus pointed out the benefits of C99 some years ago, especially
  variable declarations in loops [1]. At that time, we were not ready
  for the migration due to old compilers.

  Recently, Jakob Koschel reported a bug in list_for_each_entry(), which
  leaks the invalid pointer out of the loop [2]. In the discussion, we
  agreed that the time had come. Now that GCC 5.1 is the minimum
  compiler version, there is nothing to prevent us from going to
  -std=gnu99, or even straight to -std=gnu11.

  Discussions for a better list iterator implementation are ongoing, but
  this patch set must land first"

[1] https://lore.kernel.org/all/CAHk-=wgr12JkKmRd21qh-se-_Gs69kbPgR9x4C+Es-yJV2GLkA@mail.gmail.com/
[2] https://lore.kernel.org/lkml/[email protected]/

* tag 'kbuild-gnu11-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  Kbuild: use -std=gnu11 for KBUILD_USERCFLAGS
  Kbuild: move to -std=gnu11
  Kbuild: use -Wdeclaration-after-statement
  Kbuild: add -Wno-shift-negative-value where -Wextra is used

Author: torvalds

Documentation/process/programming-language.rst

@@ -5,9 +5,9 @@ Programming Language
 
 The kernel is written in the C programming language [c-language]_.
 More precisely, the kernel is typically compiled with ``gcc`` [gcc]_
-under ``-std=gnu89`` [gcc-c-dialect-options]_: the GNU dialect of ISO C90
-(including some C99 features). ``clang`` [clang]_ is also supported, see
-docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.
+under ``-std=gnu11`` [gcc-c-dialect-options]_: the GNU dialect of ISO C11.
+``clang`` [clang]_ is also supported, see docs on
+:ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.
 
 This dialect contains many extensions to the language [gnu-extensions]_,
 and many of them are used within the kernel as a matter of course.

Documentation/translations/it_IT/process/programming-language.rst

@@ -10,8 +10,8 @@ Linguaggio di programmazione
 
 Il kernel è scritto nel linguaggio di programmazione C [it-c-language]_.
 Più precisamente, il kernel viene compilato con ``gcc`` [it-gcc]_ usando
-l'opzione ``-std=gnu89`` [it-gcc-c-dialect-options]_: il dialetto GNU
-dello standard ISO C90 (con l'aggiunta di alcune funzionalità da C99).
+l'opzione ``-std=gnu11`` [it-gcc-c-dialect-options]_: il dialetto GNU
+dello standard ISO C11.
 Linux supporta anche ``clang`` [it-clang]_, leggete la documentazione
 :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.
 

Documentation/translations/zh_CN/process/programming-language.rst

@@ -9,8 +9,7 @@
 ============
 
 内核是用C语言 :ref:`c-language <cn_c-language>` 编写的。更准确地说，内核通常是用 :ref:`gcc <cn_gcc>`
-在 ``-std=gnu89`` :ref:`gcc-c-dialect-options <cn_gcc-c-dialect-options>` 下编译的：ISO C90的 GNU 方言（
-包括一些C99特性）
+在 ``-std=gnu11`` :ref:`gcc-c-dialect-options <cn_gcc-c-dialect-options>` 下编译的：ISO C11的 GNU 方言
 
 这种方言包含对语言 :ref:`gnu-extensions <cn_gnu-extensions>` 的许多扩展，当然，它们许多都在内核中使用。
 

Documentation/translations/zh_TW/process/programming-language.rst

@@ -12,8 +12,7 @@
 ============
 
 內核是用C語言 :ref:`c-language <tw_c-language>` 編寫的。更準確地說，內核通常是用 :ref:`gcc <tw_gcc>`
-在 ``-std=gnu89`` :ref:`gcc-c-dialect-options <tw_gcc-c-dialect-options>` 下編譯的：ISO C90的 GNU 方言（
-包括一些C99特性）
+在 ``-std=gnu11`` :ref:`gcc-c-dialect-options <tw_gcc-c-dialect-options>` 下編譯的：ISO C11的 GNU 方言
 
 這種方言包含對語言 :ref:`gnu-extensions <tw_gnu-extensions>` 的許多擴展，當然，它們許多都在內核中使用。
 

Makefile

@@ -432,7 +432,8 @@ HOSTCXX	= g++
 endif
 
 export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
-			      -O2 -fomit-frame-pointer -std=gnu89
+			      -O2 -fomit-frame-pointer -std=gnu11 \
+			      -Wdeclaration-after-statement
 export KBUILD_USERLDFLAGS :=
 
 KBUILD_HOSTCFLAGS   := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
@@ -515,7 +516,7 @@ KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
 		   -Werror=implicit-function-declaration -Werror=implicit-int \
 		   -Werror=return-type -Wno-format-security \
-		   -std=gnu89
+		   -std=gnu11
 KBUILD_CPPFLAGS := -D__KERNEL__
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
@@ -782,7 +783,7 @@ KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
 
 ifdef CONFIG_CC_IS_CLANG
 KBUILD_CPPFLAGS += -Qunused-arguments
-# The kernel builds with '-std=gnu89' so use of GNU extensions is acceptable.
+# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
 KBUILD_CFLAGS += -Wno-gnu
 # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
 # source of a reference will be _MergedGlobals and not on of the whitelisted names.

arch/arm64/kernel/vdso32/Makefile

@@ -68,7 +68,8 @@ VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                -fno-strict-aliasing -fno-common \
                -Werror-implicit-function-declaration \
                -Wno-format-security \
-               -std=gnu89
+               -Wdeclaration-after-statement \
+               -std=gnu11
 VDSO_CFLAGS  += -O2
 # Some useful compiler-dependent flags from top-level Makefile
 VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)

drivers/gpu/drm/i915/Makefile

@@ -18,6 +18,7 @@ subdir-ccflags-y += -Wno-unused-parameter
 subdir-ccflags-y += -Wno-type-limits
 subdir-ccflags-y += -Wno-missing-field-initializers
 subdir-ccflags-y += -Wno-sign-compare
+subdir-ccflags-y += -Wno-shift-negative-value
 subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 subdir-ccflags-y += $(call cc-disable-warning, frame-address)
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror

drivers/staging/greybus/tools/Makefile

@@ -12,7 +12,8 @@ CFLAGS	+= -std=gnu99 -Wall -Wextra -g \
 	    -Wredundant-decls \
 	    -Wcast-align \
 	    -Wsign-compare \
-	    -Wno-missing-field-initializers
+	    -Wno-missing-field-initializers \
+	    -Wno-shift-negative-value
 
 CC	:= $(CROSS_COMPILE)gcc
 

fs/btrfs/Makefile

@@ -17,6 +17,7 @@ subdir-ccflags-y += $(condflags)
 subdir-ccflags-y += -Wno-missing-field-initializers
 subdir-ccflags-y += -Wno-sign-compare
 subdir-ccflags-y += -Wno-type-limits
+subdir-ccflags-y += -Wno-shift-negative-value
 
 obj-$(CONFIG_BTRFS_FS) := btrfs.o
 

scripts/Makefile.extrawarn

@@ -36,6 +36,7 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 KBUILD_CFLAGS += -Wno-missing-field-initializers
 KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-type-limits
+KBUILD_CFLAGS += -Wno-shift-negative-value
 
 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1