What is the difference between g++ and gcc?

不流泪的眼

2楼-- · 2018-12-31 06:46

GCC: GNU Compiler Collection

Referrers to all the different languages that are supported by the GNU compiler.

gcc: GNU C Compiler
g++: 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 and g++ 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

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听够珍惜

3楼-- · 2018-12-31 06:48

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.

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深知你不懂我心

4楼-- · 2018-12-31 06:54

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).

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听够珍惜

5楼-- · 2018-12-31 06:56

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

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萌妹纸的霸气范

6楼-- · 2018-12-31 06:57

“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.