Question

Consider the following program:

#include <stdio.h>

int main(void)
{
    return 0;
}

When i run the following commands:

gcc memory-layout.c -o memory-layout    
size memory-layout

I get the output as:

text       data        bss        dec        hex     filename    
960        248         8          1216       4c0     memory-layout

As text area contains the executable instructions of a program, why the output is showing size of text area as 960, which is too big with respect to the size of the instructions, as far as I can count.

Answer 1

The reason is probably because the actual start of a program isn’t really the main function, but a piece of code added in the linking stage. This code setup the libraries, clears the BSS segment, and other initialization before calling your main function. There is also code to make sure that everything is cleaned up properly when you return from main.