Ubuntu编译器（C ++）

Question

I am new for Linux programming (Ubuntu server).

What difference between instructions:

c++ -c  main.cpp -o main.o -lstdc++
c++ -c  Console.cpp -o Console.o -lstdc++
c++ main.o Console.o -o App1

and this:

g++ -c  main.cpp -o main.o -lstdc++
g++ -c  Console.cpp -o Console.o -lstdc++
g++ main.o Console.o -o App1

Are these instructions the same? Is c++ instruction provides another name for g++?

Answer 1

update-alternatives --display c++

Answer 2

Yes, default is g++. You can check it using update-alternatives --display c++ ; change it via sudo update-alternatives c++

update-alternatives --config c++
There are 2 choices for the alternative c++ (providing /usr/bin/c++).

  Selection    Path              Priority   Status
------------------------------------------------------------
* 0            /usr/bin/g++       20        auto mode
  1            /usr/bin/clang++   10        manual mode
  2            /usr/bin/g++       20        manual mode

Answer 3

They both use the GNU C++ compiler I believe. So yes, they are the same.

Answer 4

They are probably the same. You can check explicitly:

which c++

/usr/bin/c++

ls -l /usr/bin/c++

/etc/alternatives/c++

ls -l etc/alternatives/c++

/usr/bin/g++

Answer 5

Yes they are the same, typing

which c++

gives you that c++ is in fact /usr/bin/c++ . then typing

ll /usr/bin/c++

will give you

lrwxrwxrwx 1 root root 21 Sep  4 17:00 /usr/bin/c++ -> /etc/alternatives/c++*

then

ll /etc/alternatives/c++

will give you

lrwxrwxrwx 1 root root 12 Sep  4 17:00 /etc/alternatives/c++ -> /usr/bin/g++*

so yes, they are the same (there is a symbolic link from c++ to g++).

Answer 6

Just look for yourself:

$ ls -l /usr/bin/c++ /usr/bin/g++ /etc/alternatives/c++

lrwxrwxrwx 1 root root 12 Jun 2 19:41 /etc/alternatives/c++ -> /usr/bin/g++*
lrwxrwxrwx 1 root root 21 Jun 2 19:41 /usr/bin/c++ -> /etc/alternatives/c++*
lrwxrwxrwx 1 root root 7 Mär 13 2012 /usr/bin/g++ -> g++-4.6*

or do:

$ c++ -v

vs.

$ g++ -v

Answer 7

g++ means the GNU C++ compiler.

c++ means a non-specific C++ compiler but it has to be linked to a specific one. If in your case, this is just a symbolic link to the GNU C++ compiler then there is no difference. However you could make the symbolic link point to a different C++ compiler.

Answer 8

Yes.

Here's how to figure out these types of things

To find the path to an executable:

which c++

To check if it's a file or a symbolic link:

ls -ald `which c++`

To check what type of file it is:

file `which c++`

To get a checksum that can be used to compare it to other files:

md5sum `which c++`

Here's one way of checking if c++ and g++ are equal:

[ `md5sum $(which c++) | cut -d' ' -f1` == `md5sum $(which g++) | cut -d' ' -f1` ] && echo Yes, equal content || echo No, unequal content