我正在使用带有C ++的gcc
构建嵌入式ARM项目:
11:01:29 ○⨠ arm-none-eabi-gcc --version
arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 4.9.3 20150529 (release) [ARM/embedded-4_9-branch revision 224288]
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
和做:
17:11:17 ○⨠ make --version
GNU Make 3.81
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
This program built for i386-apple-darwin11.3.0
我正在构建最近的一段代码,它根本不适合我 - 代码构建和部署很好,但功能不存在。 Tt没有意义,因为代码看起来完全没问题。
一位同事和我一起回顾了我们,我们发现代码没有任何问题,所以为了笑,我们决定让他构建和部署它。
它工作正常!
所以检查我们的版本,他正在运行make 4.1
。我升级到这个,嘿presto,它工作正常。
11:06:15 ○⨠ make --version
GNU Make 4.1
Built for x86_64-apple-darwin14.3.0
Copyright (C) 1988-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
我们用3.81
玩了更多,并推断出优化可能是问题所在。
但两个例子都是将-Os
传递给gcc
。
所以,我的问题是这个 - 为什么Make
会对编译器产生影响?!
当发生'Makefiles remade'时,Gnu make版本3.8.2和4.1之间的行为略有不同。例如,执行以下命令:
----- commands ----
rm ./sub.mk ./add_rule ; make -f test.mk HOSTCC=GCC
----- test.mk -----
$(info ===== test.mk(lv $(MAKELEVEL)) ==== )
$(info origin=$(origin HOSTCC))
HOSTCC = cc
$(info HOSTCC=$(HOSTCC))
$(info ------------------ )
.PHONY: all sub sub2
all:
@echo "... build $@ ..."
touch ./add_rule
@echo "*** using HOSTCC=$(HOSTCC) at all: ***"
$(MAKE) -f ./test.mk sub
@echo "*** using HOSTCC=$(HOSTCC) at all: ***"
sub:
@echo "... build $@ ..."
@echo "*** using HOSTCC=$(HOSTCC) at sub: ***"
-include sub.mk
ifneq ($(wildcard ./add_rule),)
sub.mk:
@echo "... build $@ ..."
echo "\$$$ (info --- $@(included) ---)" > $@
endif
----- end of test.mk -----
使用Ver 3.8.2 Gnu Make,最后几行控制台输出是:
....
===== test.mk(lv 1) ====
origin=environment
HOSTCC=cc
------------------
--- sub.mk(included) ---
make[1]: Entering directory `/home/user/make-test'
... build sub ...
*** using HOSTCC=cc at sub: ***
make[1]: Leaving directory `/home/user/make-test'
*** using HOSTCC=GCC at all: ***
使用ver 4.1,'cc'没有显示,但只有GCC存在。
重点是:
在版本3.8.2 Gnu make中,变量'HOSTCC'不会在sub:recipe中被覆盖,即使它是在命令行中指定的。
(在构建u-boot时我注意到了这种现象。有关'Makefile remade'的更多信息,请参阅make manual'3.5如何重新制作Makefile'。)
这种差异似乎来自ver 3.8.2 gnu make的main.c(第2091行)。
在ver 4.1代码中,putenv()不存在。
/* Reset makeflags in case they were changed. */
{
const char *pv = define_makeflags (1, 1);
char *p = alloca (sizeof ("MAKEFLAGS=") + strlen (pv) + 1);
sprintf (p, "MAKEFLAGS=%s", pv);
putenv (p); //<<=== the different point.
}