# SPDX-License-Identifier: GPL-2.0
ifneq ($(O),)
ifeq ($(origin O), command line)
        $(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
EXTRA_WARNINGS += -Wno-type-limits

# 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 ($(LLVM),)
ifneq ($(filter %/,$(LLVM)),)
LLVM_PREFIX := $(LLVM)
else ifneq ($(filter -%,$(LLVM)),)
LLVM_SUFFIX := $(LLVM)
else ifneq ($(LLVM),1)
$(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst)
endif

$(call allow-override,CC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
$(call allow-override,CLANG,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
$(call allow-override,HOSTCC,$(LLVM_PREFIX)clang$(LLVM_SUFFIX))
$(call allow-override,AR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
$(call allow-override,HOSTAR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
$(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
$(call allow-override,HOSTLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
$(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX))
$(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
$(call allow-override,LLVM_STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
$(call allow-override,LLC,$(LLVM_PREFIX)llc$(LLVM_SUFFIX))
$(call allow-override,LLVM_CONFIG,$(LLVM_PREFIX)llvm-config$(LLVM_SUFFIX))
$(call allow-override,LLVM_OBJCOPY,$(LLVM_PREFIX)llvm-objcopy$(LLVM_SUFFIX))
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)

# Host versions aren't prefixed
$(call allow-override,HOSTAR,ar)
$(call allow-override,HOSTCC,gcc)
$(call allow-override,HOSTLD,ld)

# Some tools still require Clang, LLC and/or LLVM utils
$(call allow-override,CLANG,clang)
$(call allow-override,LLC,llc)
$(call allow-override,LLVM_CONFIG,llvm-config)
$(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
$(call allow-override,LLVM_STRIP,llvm-strip)
endif

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

# Some tools require bpftool
SYSTEM_BPFTOOL	?= bpftool

RUSTC		?= rustc

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

else ifneq ($(CROSS_COMPILE),)
# Allow userspace to override CLANG_CROSS_FLAGS to specify their own
# sysroots and flags or to avoid the GCC call in pure Clang builds.
ifeq ($(CLANG_CROSS_FLAGS),)
CLANG_TARGET := $(notdir $(CROSS_COMPILE:%-=%))
CLANG_TARGET := $(subst s390-linux,s390x-linux,$(CLANG_TARGET))
CLANG_CROSS_FLAGS := --target=$(CLANG_TARGET)
GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)gcc 2>/dev/null))
ifneq ($(GCC_TOOLCHAIN_DIR),)
CLANG_CROSS_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
CLANG_CROSS_FLAGS += --sysroot=$(shell $(CROSS_COMPILE)gcc -print-sysroot)
CLANG_CROSS_FLAGS += --gcc-toolchain=$(realpath $(GCC_TOOLCHAIN_DIR)/..)
endif # GCC_TOOLCHAIN_DIR
endif # CLANG_CROSS_FLAGS
CFLAGS += $(CLANG_CROSS_FLAGS)
AFLAGS += $(CLANG_CROSS_FLAGS)
else
CLANG_CROSS_FLAGS :=
endif # CROSS_COMPILE

# 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://lore.kernel.org/lkml/9a8748490611281710g78402fbeh8ff7fcc162dbcbca@mail.gmail.com/
# 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

# Beautify output
# ---------------------------------------------------------------------------
#
# Most of build commands in Kbuild start with "cmd_". You can optionally define
# "quiet_cmd_*". If defined, the short log is printed. Otherwise, no log from
# that command is printed by default.
#
# e.g.)
#    quiet_cmd_depmod = DEPMOD  $(MODLIB)
#          cmd_depmod = $(srctree)/scripts/depmod.sh $(DEPMOD) $(KERNELRELEASE)
#
# A simple variant is to prefix commands with $(Q) - that's useful
# for commands that shall be hidden in non-verbose mode.
#
#    $(Q)$(MAKE) $(build)=scripts/basic
#
# To put more focus on warnings, be less verbose as default
# Use 'make V=1' to see the full commands

ifeq ($(V),1)
  quiet =
  Q =
else
  quiet = quiet_
  Q = @
endif

# If the user is running make -s (silent mode), suppress echoing of commands
# make-4.0 (and later) keep single letter options in the 1st word of MAKEFLAGS.
ifeq ($(filter 3.%,$(MAKE_VERSION)),)
short-opts := $(firstword -$(MAKEFLAGS))
else
short-opts := $(filter-out --%,$(MAKEFLAGS))
endif

ifneq ($(findstring s,$(short-opts)),)
  silent=1
  quiet=silent_
endif

export quiet Q

#
# 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_CLANG    = @echo '  CLANG   '$@;
	QUIET_AR       = @echo '  AR      '$@;
	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    '$@;
	QUIET_BISON    = @echo '  BISON   '$@;
	QUIET_GENSKEL  = @echo '  GENSKEL '$@;

	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 := \#