[PATCH] kbuild: drop -Wdeclaration-after-statement

[Alexey Dobriyan]

Putting declarations in the beginning of the block is an afterfact from
single pass compiler era. Compiler would parse all declarations, layout
stack frame and proceed to generate code.

In C initialisers can be arbitrarily complex so there is no fundamental
distinction between initialiser and regular code.
-Wno-declaration-after-statement creates such distinction which is
entirely artificial.

This will save LOC in the long run because people would write code like
this:

	int a = f();

This will make one rare class of bugs even more rare:

	int a;
	...
	f(&a);	// bug, typo, should be f(&x)
	...
	a = g();

If declarations are allowed anywhere, the above would be written as

	f(&a);
	int a = g();

and it would not compile because "a" lives for less LOC window.

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

 Makefile                          |    6 +-----
 arch/arm64/kernel/vdso32/Makefile |    2 --
 tools/power/acpi/Makefile.config  |    1 -
 tools/power/cpupower/Makefile     |    1 -
 tools/scripts/Makefile.include    |    1 -
 5 files changed, 1 insertion(+), 10 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -452,8 +452,7 @@ HOSTRUSTC = rustc
 HOSTPKG_CONFIG	= pkg-config
 
 KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
-			 -O2 -fomit-frame-pointer -std=gnu11 \
-			 -Wdeclaration-after-statement
+			 -O2 -fomit-frame-pointer -std=gnu11
 KBUILD_USERCFLAGS  := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
 KBUILD_USERLDFLAGS := $(USERLDFLAGS)
 
@@ -1011,9 +1010,6 @@ endif
 # arch Makefile may override CC so keep this after arch Makefile is included
 NOSTDINC_FLAGS += -nostdinc
 
-# warn about C99 declaration after statement
-KBUILD_CFLAGS += -Wdeclaration-after-statement
-
 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
 KBUILD_CFLAGS += -Wvla
 
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -68,11 +68,9 @@ VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                -fno-strict-aliasing -fno-common \
                -Werror-implicit-function-declaration \
                -Wno-format-security \
-               -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,)
 VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
 VDSO_CFLAGS += -fno-strict-overflow
 VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
--- a/tools/power/acpi/Makefile.config
+++ b/tools/power/acpi/Makefile.config
@@ -63,7 +63,6 @@ OPTIMIZATION := $(call cc-supports,-Os,-O2)
 
 WARNINGS := -Wall
 WARNINGS += $(call cc-supports,-Wstrict-prototypes)
-WARNINGS += $(call cc-supports,-Wdeclaration-after-statement)
 
 KERNEL_INCLUDE := $(OUTPUT)include
 ACPICA_INCLUDE := $(srctree)/../../../drivers/acpi/acpica
--- a/tools/power/cpupower/Makefile
+++ b/tools/power/cpupower/Makefile
@@ -118,7 +118,6 @@ OPTIMIZATION := $(call cc-supports,-Os,-O2)
 
 WARNINGS := -Wall -Wchar-subscripts -Wpointer-arith -Wsign-compare
 WARNINGS += $(call cc-supports,-Wno-pointer-sign)
-WARNINGS += $(call cc-supports,-Wdeclaration-after-statement)
 WARNINGS += -Wshadow
 
 override CFLAGS += -DVERSION=\"$(VERSION)\" -DPACKAGE=\"$(PACKAGE)\" \
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -21,7 +21,6 @@ endif
 # Include saner warnings here, which can catch bugs:
 #
 EXTRA_WARNINGS := -Wbad-function-cast
-EXTRA_WARNINGS += -Wdeclaration-after-statement
 EXTRA_WARNINGS += -Wformat-security
 EXTRA_WARNINGS += -Wformat-y2k
 EXTRA_WARNINGS += -Winit-self