c ++是否允许在任何功能之外调用函数？

Question

I have code

#include <stdlib.h>

void *gg = malloc(55);

int main(int argc, char **argv)
{
        return 0;
}

gcc fail to compile but g++ works.

So, I just want to make sure that the malloc calling happens before main is exectued.

Answer 1

What you do is allowed in C++. The C++ standard has a whole section on "Dynamic initialization of non-local variables" .

Looking at the assembly generated by GCC for your code is instructive:

Here the initializers are called through two generated functions, _GLOBAL__sub_I_gg (which is called before main ) which in turn calls __static_initialization_and_destruction_0 .

It is within the body of the latter function you will find the call to malloc .