C++ Makefile修改支持c++11
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Makefile modification to support c++11
提问by Ari
I am able to compile a single file using gcc with -std=c++0x option. But I can't do this through makefile. Here are the set of flags in my makefile (which after make complains about c++11 keywords):
我可以使用带有 -std=c++0x 选项的 gcc 编译单个文件。但是我不能通过makefile来做到这一点。这是我的 makefile 中的一组标志（在 make 之后抱怨 c++11 关键字）：
MACHINE = $(shell echo `uname -s`-`uname -m` | sed "s/ //g")
CCC = CC
CCC = g++
CFLAGS = -O3
CFLAGS = -std=c++0x
CFLAGS = -pg -D_DEBUG -g -c -Wall
LFLAGS = -O
LFLAGS = -pg -g
What am I missing?
我错过了什么？
Edit: I changed it to the following, but I still get compile errors, which I don't get with command line gcc invocation.
编辑：我将其更改为以下内容，但仍然出现编译错误，而命令行 gcc 调用不会出现这些错误。
CXXFLAGS=-O3 -std=c++0x -pg -D_DEBUG -g -c -Wall
回答by mfontanini
This way your makefile will use all of your CFLAGS:
这样你的 makefile 将使用你所有的CFLAGS：
CFLAGS=-O3 -std=c++0x -pg -D_DEBUG -g -c -Wall
You're overriding them with each "CFLAGS=..." declaration.
您正在使用每个“CFLAGS=...”声明覆盖它们。
Moreover, it should be CXXFLAGS, not CFLAGS. CFLAGSis for C applications.
而且，应该是CXXFLAGS，不是CFLAGS。CFLAGS用于 C 应用程序。
As @Florian Sowade said, you could use CFLAGS += -O3 -std....(or CXXFLAGS..), so that users can provide their own flags when executing make.
正如@Florian Sowade 所说，您可以使用CFLAGS += -O3 -std....（或 CXXFLAGS ..），以便用户在执行 make 时可以提供自己的标志。
回答by Ari
You can keep it in multiple lines, but you probably want to append, not to assign:
您可以将其保存在多行中，但您可能想要append，而不是分配：
# e.g.
CFLAGS += -O3
CFLAGS += -std=c++0x
CFLAGS += -pg -D_DEBUG -g -c -Wall
回答by Jonathan Wakely
Where did you get that mess from? That makefile was wrong long before you modified it for C++11.
你从哪里弄来的这些烂摊子？在你为 C++11 修改它之前，那个 makefile 是错误的。
Let's start with the first line:
让我们从第一行开始：
MACHINE = $(shell echo `uname -s`-`uname -m` | sed "s/ //g")
Try running the command echo `uname -s`-`uname -m`and you'll see if has no spaces in anyway, so what's the point in the sedcommand?
尝试运行该命令echo `uname -s`-`uname -m`，您将看到无论如何都没有空格，那么该sed命令有什么意义呢？
Maybe you want this:
也许你想要这个：
MACHINE = $(shell uname -s -m | sed "s/ /-/g")
That only runs two processes (uname and sed) not four (two unames, echo and sed)
只运行两个进程（uname 和 sed）而不是四个（两个 unames、echo 和 sed）
If you're using GNU make it should be
如果你使用 GNU make 应该是
MACHINE := $(shell uname -s -m | sed "s/ /-/g")
So it's only run once.
所以它只运行一次。
CCC = CC
What is CC?
什么是CC？
CCC = g++
Oh, it doesn't matter, you've replaced the value anyway.
The conventional make variable for the C++ compiler is CXX
哦，没关系，反正你已经替换了值。C++ 编译器的常规 make 变量是CXX
CFLAGS = -O3
CFLAGS = -std=c++0x
CFLAGS = -pg -D_DEBUG -g -c -Wall
As others have pointed out, you set CFLAGS, then set it to something different, then to something different. Only the last value will be kept.
正如其他人指出的那样，您设置了 CFLAGS，然后将其设置为不同的内容，然后再设置为不同的内容。只会保留最后一个值。
LFLAGS = -O
LFLAGS = -pg -g
Same here, and what is LFLAGS? Do you mean LDFLAGS?
这里也一样，什么是LFLAGS？你的意思是LDFLAGS？
A good way to debug makefiles is to create a target to print out the variables you are setting, to check they have the values you expect:
调试 makefile 的一个好方法是创建一个目标来打印您正在设置的变量，以检查它们是否具有您期望的值：
print-vars:
echo CFLAGS is $(CFLAGS)
echo LDFLAGS is $(LDFLAGS)
