问题
Im terrible with understanding what goes on behind the scenes when running programs.
On my schools server, I just use gcc and pretty much the same code every time I need to make a makefile lol.
I downloaded my program to debug it in NetBeans and after hours/days.. I finally ALMOST have everything working.
After looking at a few posts on here and other sites, I saw that for some reason I need to use g++ instead of gcc to compile since I'm using a MacBook. Which I don't really understand.. But if I change gcc to g++ and run this line in my makefile:
Edit:
g++ -c $< -o $@ -std=c++0x -lstdc++
I get an error. But if I remove "-std=c++0x" and run make again.. Everything is good to go.
But if I run my "make clean" I have to do it over again..
Will this mess everything up when I put the program back on my schools server? Or should it be fine as long as I have a makefile on the server that is different from the makefile on my MacBook?
Can someone help expelling why this is happening and how I could possibly fix it?
Here's my makefile the first time I run make:
OBJECTS = Ammunition.o Armor.o Consumable.o
HEADERS = Ammunition.h Armor.h Consumable.h
all: Jhack
%.o: %.cpp $(HEADERS)
g++ -c $< -o $@ -std=c++0x
Jhack: $(OBJECTS) main.o
g++ -o Jhack $^
clean:
rm -f *.o Jhack
run: Jhack
./Jhack
Thanks.
回答1:
First, for Linux GNU C compilers, gcc is a C compiler whereas g++ is a C++ compiler. Which means when you compile with gcc, all your error messages are basically saying, "I don't know what all this strange syntax is."
Your school isn't using a Linux server, or "gcc" there may be a link to a c++ compiler. Or the core make rules are replacing your compiler choice with g++.
I don't think there's all that much you need to worry about in this regard. Just remember the difference, and possibly replace gcc and g++ with a macro in your makefile.
As for the -std option, that's choosing which version of the C++ standard you want to compile against. Since some of your code requires 2011 C++ standard, you need to specify that with your -std option. If you look at your g++ man pages, it should tell you what options are supported.
You can try -std=c++0x or -std=c++11 or -std=gnu++11
Any of those should give you the functionality you require. Based on what I've searched for, you don't need to specify -std=stdc++ since i think that's included by g++ by default.
回答2:
You're probably usign an old, experimental version of GCC. "ConceptGCC" from the comments, and the -std=c++0x flag tell me so. Modern GCC variants would use -std=c++11 instead.
You never need to use g++ instead of gcc. It's just a convenience, so you don't need to pass all gcc options required to compile C++. In particular, -lstdc++ is implied by g++.
Since you're using a rather unusual "ConceptGCC" package, I'd suggest you replace it by the normal GCC version 4.8.0.
To debug what make is trying to do, run make -n. You can then run these commands manually to see precisely what happens.
回答3:
Justin, I don't know what std=c++0x does (I looked it up but I don't know what "experimental features" are possibly being affected...), but if removing it helps, then just remove it.
What you have described sounds to me like some objects require the std=c++0x flag and some won't build with it. Would you try just removing the flag, cleaning and then rebuilding?
Worst case - remove the variable rule and write three different rules for each of your object files.
来源：https://stackoverflow.com/questions/16272046/why-do-i-have-to-double-run-make-to-fully-compile-my-program-gnu-c