1.简化主机架构名称(HOSTARCH)和主机操作系统名称(HOSTOS)------L31~L40
HOSTARCH := $(shell uname -m | \
sed -e s/i.86/i386/ \
-e s/sun4u/sparc64/ \
-e s/arm.*/arm/ \
-e s/sa110/arm/ \
-e s/powerpc/ppc/ \
-e s/macppc/ppc/)
HOSTOS := $(shell uname -s | tr '[:upper:]' '[:lower:]' | \
sed -e 's/\(cygwin\).*/cygwin/')
在此使用了 shell 命令 sed ,此命令会把主机架构名“i686”替换为“i386”,把主机操作系统“Linux”替换为“linux”,目的是尽量统一主机的架构名和操作系统类型。
2.指定编译链接时目标文件的输出目录
ifdef O
ifeq ("$(origin O)", "command line")
BUILD_DIR := $(O)
endif
endif
ifneq ($(BUILD_DIR),)
saved-output := $(BUILD_DIR)
# Attempt to create a output directory.
$(shell [ -d ${BUILD_DIR} ] || mkdir -p ${BUILD_DIR})
# Verify if it was successful.
BUILD_DIR := $(shell cd $(BUILD_DIR) && /bin/pwd)
$(if $(BUILD_DIR),,$(error output directory "$(saved-output)" does not exist))
endif # ifneq ($(BUILD_DIR),)
有两种方式指定输出文件的目录:
(1)Add O= to the make command line
# 'make O=/tmp/build all'
(2) Set environement variable BUILD_DIR to point to the desired location
# 'export BUILD_DIR=/tmp/build'
# 'make'