# SPDX-License-Identifier: GPL-2.0
ifneq ($(O),)
ifeq ($(origin O), command line)
	dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
	ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
	COMMAND_O := O=$(ABSOLUTE_O)
ifeq ($(objtree),)
	objtree := $(O)
endif
endif
endif

# check that the output directory actually exists
ifneq ($(OUTPUT),)
OUTDIR := $(shell cd $(OUTPUT) && pwd)
$(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))
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
EXTRA_WARNINGS += -Wmissing-declarations
EXTRA_WARNINGS += -Wmissing-prototypes
EXTRA_WARNINGS += -Wnested-externs
EXTRA_WARNINGS += -Wno-system-headers
EXTRA_WARNINGS += -Wold-style-definition
EXTRA_WARNINGS += -Wpacked
EXTRA_WARNINGS += -Wredundant-decls
EXTRA_WARNINGS += -Wstrict-prototypes
EXTRA_WARNINGS += -Wswitch-default
EXTRA_WARNINGS += -Wswitch-enum
EXTRA_WARNINGS += -Wundef
EXTRA_WARNINGS += -Wwrite-strings
EXTRA_WARNINGS += -Wformat

# Makefiles suck: This macro sets a default value of $(2) for the
# variable named by $(1), unless the variable has been set by
# environment or command line. This is necessary for CC and AR
# because make sets default values, so the simpler ?= approach
# won't work as expected.
define allow-override
  $(if $(or $(findstring environment,$(origin $(1))),\
            $(findstring command line,$(origin $(1)))),,\
    $(eval $(1) = $(2)))
endef

ifneq ($(LLVM),)
$(call allow-override,CC,clang)
$(call allow-override,AR,llvm-ar)
$(call allow-override,LD,ld.lld)
$(call allow-override,CXX,clang++)
$(call allow-override,STRIP,llvm-strip)
else
# Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
$(call allow-override,CC,$(CROSS_COMPILE)gcc)
$(call allow-override,AR,$(CROSS_COMPILE)ar)
$(call allow-override,LD,$(CROSS_COMPILE)ld)
$(call allow-override,CXX,$(CROSS_COMPILE)g++)
$(call allow-override,STRIP,$(CROSS_COMPILE)strip)
endif

CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)

ifneq ($(LLVM),)
HOSTAR  ?= llvm-ar
HOSTCC  ?= clang
HOSTLD  ?= ld.lld
else
HOSTAR  ?= ar
HOSTCC  ?= gcc
HOSTLD  ?= ld
endif

ifeq ($(CC_NO_CLANG), 1)
EXTRA_WARNINGS += -Wstrict-aliasing=3
endif

# Hack to avoid type-punned warnings on old systems such as RHEL5:
# We should be changing CFLAGS and checking gcc version, but this
# will do for now and keep the above -Wstrict-aliasing=3 in place
# in newer systems.
# Needed for the __raw_cmpxchg in tools/arch/x86/include/asm/cmpxchg.h
#
# See https://lkml.org/lkml/2006/11/28/253 and https://gcc.gnu.org/gcc-4.8/changes.html,
# that takes into account Linus's comments (search for Wshadow) for the reasoning about
# -Wshadow not being interesting before gcc 4.8.

ifneq ($(filter 3.%,$(MAKE_VERSION)),)  # make-3
EXTRA_WARNINGS += -fno-strict-aliasing
EXTRA_WARNINGS += -Wno-shadow
else
EXTRA_WARNINGS += -Wshadow
endif

ifneq ($(findstring $(MAKEFLAGS), w),w)
PRINT_DIR = --no-print-directory
else
NO_SUBDIR = :
endif

ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)
  silent=1
endif

#
# Define a callable command for descending to a new directory
#
# Call by doing: $(call descend,directory[,target])
#
descend = \
	+mkdir -p $(OUTPUT)$(1) && \
	$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2)

QUIET_SUBDIR0  = +$(MAKE) $(COMMAND_O) -C # space to separate -C and subdir
QUIET_SUBDIR1  =

ifneq ($(silent),1)
  ifneq ($(V),1)
	QUIET_CC       = @echo '  CC       '$@;
	QUIET_CC_FPIC  = @echo '  CC FPIC  '$@;
	QUIET_AR       = @echo '  AR       '$@;
	QUIET_LINK     = @echo '  LINK     '$@;
	QUIET_MKDIR    = @echo '  MKDIR    '$@;
	QUIET_GEN      = @echo '  GEN      '$@;
	QUIET_SUBDIR0  = +@subdir=
	QUIET_SUBDIR1  = ;$(NO_SUBDIR) \
			  echo '  SUBDIR   '$$subdir; \
			 $(MAKE) $(PRINT_DIR) -C $$subdir
	QUIET_FLEX     = @echo '  FLEX     '$@;
	QUIET_BISON    = @echo '  BISON    '$@;

	descend = \
		+@echo	       '  DESCEND  '$(1); \
		mkdir -p $(OUTPUT)$(1) && \
		$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2)

	QUIET_CLEAN    = @printf '  CLEAN    %s\n' $1;
	QUIET_INSTALL  = @printf '  INSTALL  %s\n' $1;
	QUIET_UNINST   = @printf '  UNINST   %s\n' $1;
  endif
endif

pound := \#