Conditional Rules

注意：
- Condition 语句里面全部不能用 Tab 缩进, 你看到的 Makefile 如果好像有 "Tab", 那全部是空格
- 使用 Tab 会报错：*** commands commence before first target

1 ifeq / else / endif

# build flags
ifeq ($(TARGET_OS),darwin)
    LDFLAGS += -rpath $(CUDA_PATH)/lib
    CCFLAGS += -arch $(HOST_ARCH)
else ifeq ($(HOST_ARCH)-$(TARGET_ARCH)-$(TARGET_OS),x86_64-armv7l-linux)
    LDFLAGS += --dynamic-linker=/lib/ld-linux-armhf.so.3
    CCFLAGS += -mfloat-abi=hard
else ifeq ($(TARGET_OS),android)
    LDFLAGS += -pie
    CCFLAGS += -fpie -fpic -fexceptions
endif

 

2 ifneq / else / endif

HOST_ARCH   := $(shell uname -m)
TARGET_ARCH ?= $(HOST_ARCH)
temp := $(filter $(TARGET_ARCH),x86_64 aarch64 sbsa ppc64le armv7l)

ifneq (,$(filter $(TARGET_ARCH),x86_64 aarch64 sbsa ppc64le armv7l))
    ifneq ($(TARGET_ARCH),$(HOST_ARCH))
        ifneq (,$(filter $(TARGET_ARCH),x86_64 aarch64 sbsa ppc64le))
            TARGET_SIZE := 64
        else ifneq (,$(filter $(TARGET_ARCH),armv7l))
            TARGET_SIZE := 32
        endif
    else
        TARGET_SIZE := $(shell getconf LONG_BIT)
    endif
else
    $(error ERROR - unsupported value $(TARGET_ARCH) for TARGET_ARCH!)
endif

 

3 ifdef / else / endif

ifdef TARGET_OVERRIDE # cuda toolkit targets override
    NVCCFLAGS += -target-dir $(TARGET_OVERRIDE)
endif