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如果编译器选项与以前使用的不同,则使目标过期

gnu-make makefile shell bash linux

jfMR · 技术社区 · 6 年前

请考虑下面的目录树,它是一个化妆玩具示例,说明了要解决的问题:

- Makefile
- lib.c
+ foo/
   |-- config.mk
+ bar/
   |-- config.mk

内容 foo/config.mk :
```
CFLAGS += -DFOO
```
内容 bar/config.mk
```
CFLAGS += -DBAR
```

使命感 make 具有 Makefile foo 和 bar foo/config.mk 和包括在内(通过 include directive lib.o 正在建造,即:

# build lib.o with the macro FOO defined
$ make foo

# build lib.o with the macro BAR defined
$ make bar

# build lib.o with both the macros FOO and BAR defined
$ make foo bar
$ make bar foo

建筑的默认规则使用变量 COMPILE.c ,定义为(根据调用 制作 有选择权 --print-data-base

COMPILE.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c

扩张 编译.c 除其他外,取决于变量的值 CFLAGS foo/config.mk bar/config.mk 由于这些生成文件修改了 CFLAGS 变量

我想要达到的是对待目标 自由党 作为如果变量展开,则返回目标 编译.c 当前使用的与上一版本的不同 . 例如:

$ make foo

# It shouldn't rebuild anything since lib.o should be up-to-date
$ make foo

# It should rebuild lib.o since it should be out-of-date
$ make bar

# It should rebuild lib.o since it is again out-of-date
$ make foo bar

# It shouldn't rebuild lib.o since it is up-to-date
$ make bar foo

This solution

3 回复 | 直到 6 年前

Renaud Pacalet 6 年前

ifeq ($(filter foo,$(MAKECMDGOALS)),foo)
include foo/config.mk
endif
ifeq ($(filter bar,$(MAKECMDGOALS)),bar)
include bar/config.mk
endif
-include old_compile.mk

COMPILE.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c

ifneq ($(COMPILE.c),$(OLD_COMPILE.c))
FORCE := force
endif

lib.o: lib.c $(FORCE)
    $(COMPILE.c) $< -o $@
    echo 'OLD_COMPILE.c := $(COMPILE.c)' > old_compile.mk

.PHONY: foo bar all force

foo bar all: lib.o

演示:

$ make foo
cc -DFOO   -c lib.c -o lib.o
echo 'OLD_COMPILE.c := cc -DFOO   -c' > old_compile.mk
$ make foo
make: Nothing to be done for 'foo'.
$ make foo bar
cc -DFOO -DBAR   -c lib.c -o lib.o
echo 'OLD_COMPILE.c := cc -DFOO -DBAR   -c' > old_compile.mk
make: Nothing to be done for 'bar'.
$ make bar foo
make: Nothing to be done for 'bar'.
make: Nothing to be done for 'foo'.

n. m. could be an AI 6 年前

这是我的原始模型,它直接在文件名中编码编译器/链接器标志。这只是一个想法,一个实际的实现应该更健壮一些。

empty:=
space:= $(empty) $(empty)
comma:= ,

LDFLAGS_NS=$(subst $(space),$(comma),$(LDFLAGS))
CFLAGS_NS=$(subst $(space),$(comma),$(CFLAGS))

EXEDIR=./test-exedir-cflags=$(CFLAGS_NS)-ldflags=$(LDFLAGS_NS)
EXEDIR_PAT=./test-exedir-*
OBJDIR=./test-objdir-cflags=$(CFLAGS_NS)
OBJDIR_PAT=./test-objdir-*

test.exe: $(EXEDIR)/test.exe
    rm -f test
    ln -s $< $@

$(EXEDIR)/test.exe: test.o
    rm -rf $(EXEDIR_PAT)
    mkdir $(EXEDIR)
    cc $(LDFLAGS) -o $@ $<

test.o: $(OBJDIR)/test.o
    rm -f test.o
    ln -s $< $@

$(OBJDIR)/test.o: test.c
    rm -rf $(OBJDIR_PAT)
    mkdir $(OBJDIR)
    cc -c $(CFLAGS) -o $@ $<

使用hello world test.c文件和以下命令进行测试:

make test.exe
make test.exe
make test.exe CFLAGS="-g -Wall"
make test.exe CFLAGS="-g -Wall"
make test.exe

jfMR 6 年前

到目前为止,我的方法是生成一个文件, cc-options-dump COMPILE.c 每次变量 lib.o 是建的。

编译.c 抄送选项转储 ,如果有(即,如果文件确实存在)。

.PHONY: foo bar require-rebuild cc-options-dump

# include the xxx/config.mk files
# sort built-in function to make it independent of the order (i.e., "foo bar" or "bar foo")
$(foreach opt,$(sort $(MAKECMDGOALS)),$(eval include $(opt)/config.mk))

# obtain the MD5 hash of the previously used flags
ifneq (,$(wildcard cc-options-dump))
prev-cc-options-hash := $(shell md5sum cc-options-dump | cut -f1 -d' ')
endif

# obtain the MD5 hash of the current flags
curr-cc-options-hash := $(shell echo "$(COMPILE.c)" | md5sum | cut -f1 -d' ')

# Do these hashes differ?
ifneq ($(prev-cc-options-hash),$(curr-cc-options-hash))
# keep track of the fact that a rebuilt needs to be triggered
does-need-rebuild := require-rebuild
# just for displaying information
$(info Rebuild required)
else
$(info Rebuild not required)
endif

# make both targets foo and bar dependent on the file with the flags
# so that it has to be generated, since it is a phony target as well 
foo bar: cc-options-dump

# lib.o has now an additional prerequisite for determining whether it need to be rebuilt
lib.o: $(does-need-rebuild)

# save the used compiler flags for comparing them with the future flags
cc-options-dump: lib.o
    @echo '$(COMPILE.c)' >$@

make 针对目标 foo 和/或 bar 据我所知,与所需的一致:

$ make foo
Rebuild required
cc -DFOO   -c -o lib.o lib.c

$ make foo
Rebuild not required

$ make bar
Rebuild required
cc -DBAR   -c -o lib.o lib.c

$ make bar
Rebuild not required

$ make foo bar
Rebuild required
cc -DBAR -DFOO   -c -o lib.o lib.c

$ make bar foo
Rebuild not required

使用 sort 内置功能对于上述最后两种情况的正常工作至关重要。

如果有人能提供一个更优雅的解决方案,那就太好了。