Thread: program execution begins

Originally Posted by Kittu20

This means that the compiler/linker allocates memory address for a global variable and assigns a value to it before the main function is executed.

It's the compiler that initializes x during the compile process. Look at the source file and the assembler code:

Source file:

Code:

int x = 20;

int main(void)
{

  return 0;
}

Compile command: [gcc -s global.c]

Look at the section"x:"

Assembler output:

Code:

        .file   "global.c"
        .text
        .globl  x
        .data
        .align 4
        .type   x, @object
        .size   x, 4
x:
        .long   20
        .text
        .globl  main
        .type   main, @function
main:
.LFB0:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    $0, %eax
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   main, .-main
        .ident  "GCC: (Debian 12.2.0-14) 12.2.0"
        .section        .note.GNU-stack,"",@progbits

The linker would resolve the definition of the global variable, and it's use in main() if used.