What is the difference between g++ and gcc? Which one of them should be used for general c++ development?
10 Answers
gcc
and g++
are compiler-drivers of the GNU Compiler Collection (which was once upon a time just the GNU C Compiler).
Even though they automatically determine which backends (cc1
cc1plus
...) to call depending on the file-type, unless overridden with -x language
, they have some differences.
The probably most important difference in their defaults is which libraries they link against automatically.
According to GCC's online documentation link options and how g++ is invoked, g++
is equivalent to gcc -xc++ -lstdc++ -shared-libgcc
(the 1st is a compiler option, the 2nd two are linker options). This can be checked by running both with the -v
option (it displays the backend toolchain commands being run).
GCC: GNU Compiler Collection
- Referrers to all the different languages that are supported by the GNU compiler.
gcc
: GNU C Compilerg++
: GNU C++ Compiler
The main differences:
gcc
will compile:*.c\*.cpp
files as C and C++ respectively.g++
will compile:*.c\*.cpp
files but they will all be treated as C++ files.- Also if you use
g++
to link the object files it automatically links in the std C++ libraries (gcc
does not do this). gcc
compiling C files has fewer predefined macros.gcc
compiling*.cpp
andg++
compiling*.c\*.cpp
files has a few extra macros.
Extra Macros when compiling *.cpp
files:
#define __GXX_WEAK__ 1
#define __cplusplus 1
#define __DEPRECATED 1
#define __GNUG__ 4
#define __EXCEPTIONS 1
#define __private_extern__ extern
For c++ you should use g++.
It's the same compiler (e.g. the GNU compiler collection). GCC or G++ just choose a different front-end with different default options.
In a nutshell: if you use g++ the frontend will tell the linker that you may want to link with the C++ standard libraries. The gcc frontend won't do that (also it could link with them if you pass the right command line options).
What is the difference between g++
and gcc
?
gcc
has evolved from a single language "GNU C Compiler" to be a multi-language "GNU Compiler Collection". The term "GNU C Compiler" is still used sometimes in the context of C programming.
The g++
is the C++ compiler for the GNU Compiler Collection. Like gnat
is the Ada compiler for gcc
. see Using the GNU Compiler Collection (GCC)
For example, the Ubuntu 16.04 and 18.04 man g++
command returns the GCC(1)
manual page.
The Ubuntu 16.04 and 18.04 man gcc
states that ...
g++
accepts mostly the same options asgcc
and that the default ...
... use of
gcc
does not add the C++ library.g++
is a program that calls GCC and automatically specifies linking against the C++ library. It treats .c, .h and .i files as C++ source files instead of C source files unless -x is used. This program is also useful when precompiling a C header file with a .h extension for use in C++ compilations.
Search the gcc
man pages for more details on the option variances between gcc
and g++
.
Which one should be used for general c++ development?
Technically, either gcc
or g++
can be used for general C++ development with applicable option settings. However, the g++
default behavior is naturally aligned to a C++ development.
The Ubuntu 18.04 'gcc' man page added, and Ubuntu 20.04 continues to have, the following paragraph:
The usual way to run GCC is to run the executable called
gcc
, ormachine-gcc
when cross-compiling, ormachine-gcc-version
to run a specific version of GCC. When you compile C++ programs, you should invoke GCC asg++
instead.
Although the gcc and g++ commands do very similar things, g++ is designed to be the command you'd invoke to compile a C++ program; it's intended to automatically do the right thing.
Behind the scenes, they're really the same program. As I understand, both decide whether to compile a program as C or as C++ based on the filename extension. Both are capable of linking against the C++ standard library, but only g++ does this by default. So if you have a program written in C++ that doesn't happen to need to link against the standard library, gcc will happen to do the right thing; but then, so would g++. So there's really no reason not to use g++ for general C++ development.
I became interested in the issue and perform some experiments
I found that description here, but it is very short.
Then I tried to experiment with gcc.exe and g++.exe on my windows machine:
$ g++ --version | head -n1 g++.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3 $ gcc --version | head -n1 gcc.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
I tried to compile c89, c99, and c++1998 simple test files and It's work well for me with correct extensions matching for language
gcc -std=c99 test_c99.c gcc -std=c89 test_c89.c g++ -std=c++98 test_cpp.cpp gcc -std=c++98 test_cpp.cpp
But when I try to run "gnu compiler collection" tool in that fashion:
$ gcc -std=c++98 test_cpp.c cc1.exe: warning: command line option '-std=c++98' is valid for C++/ObjC++ but not for C [enabled by default]
But this one still work with no errors
$ gcc -x c++ -std=c++98 test_cpp.c
And this also
$ g++ -std=c++0x test_cpp_11.cpp
p.s. Test files
$ cat test_c89.c test_c99.c test_cpp.cpp
// C89 compatible file
int main()
{
int x[] = {0, 2};
return sizeof(x);
}
// C99 compatible file
int main()
{
int x[] = {[1]=2};
return sizeof(x);
}
// C++1998,2003 compatible file
class X{};
int main()
{
X x;
return sizeof(x);
}
// C++11
#include <vector>
enum class Color : int{red,green,blue}; // scoped enum
int main()
{
std::vector<int> a {1,2,3}; // bracket initialization
return 0;
}
Findings:
If look at process tree then it seems that gcc, and g++ is backend to other tools, which in my environment are: cc1plus.exe, cc1.exe, collect2.exe, as.exe, ld.exe
gcc works fine as metatool for if you have correct extension or set correct -std -x flags. See this
“GCC” is a common shorthand term for the GNU Compiler Collection. This is both the most general name for the compiler, and the name used when the emphasis is on compiling C programs (as the abbreviation formerly stood for “GNU C Compiler”).
When referring to C++ compilation, it is usual to call the compiler “G++”. Since there is only one compiler, it is also accurate to call it “GCC” no matter what the language context; however, the term “G++” is more useful when the emphasis is on compiling C++ programs.
You could read more here.
I was testing gcc and g++ in a linux system. By using MAKEFILE, I can define the compliler used by "GNU make". I tested with the so called "dynamic memory" locating feature of "C plus plus" by :
int main(){
int * myptr = new int;
* myptr = 1;
printf("myptr[0] is %i\n",*myptr);
return 0;
}
Only g++ can successfully compile on my computer while gcc will report error
undefined reference to `operator new(unsigned long)'
So my own conclusion is gcc does not fully support "C plus plus". It seems that choosing g++ for C++ source files is a better option.