Using C on x86-64, why emit .text for global data?

[Bob Plantz]

First, I do understand that using global data is usually a bad idea, but I want to explain the mechanism of global data to students.

I'm using gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1) for x86-64 code.

I'm looking at how global variables are handled in position independent code.

Test program:

int x = 12;
int y = 34;
int z;

int main(void)
{
  z = x + y;
  printf("%i + %i = %i\n", x, y, z);

  return 0;
}

Why does gcc emit an extra .text before the global data?

.file "globalData.c"
.text
.globl x
.data
.align 4
.type x, @object
.size x, 4
x:
.long 12
.globl y
.align 4
.type y, @object
.size y, 4
y:
.long 34
.comm z,4,4
.section .rodata
.LC0:
.string "%i + %i = %i\n"
.text
.globl main
.type main, @function
main:

I can remove the .text at the beginning,

.file "globalData.c"
.globl x
.data
.align 4
.type x, @object
.size x, 4
x:
.long 12
.globl y
.align 4
.type y, @object
.size y, 4
y:
.long 34
.comm z,4,4
.section .rodata
.LC0:
.string "%i + %i = %i\n"
.text
.globl main
.type main, @function
main:

and readelf shows that the assembler, as, produces exactly the same object file.

I can even see that .comm and .section .rodata do not need to be within a .text or .data region,

.file "globalData.c"
.comm z,4,4
.section .rodata
.LC0:
.string "%i + %i = %i\n"
.globl x
.data
.align 4
.type x, @object
.size x, 4
x:
.long 12
.globl y
.align 4
.type y, @object
.size y, 4
y:
.long 34
.text
.globl main
.type main, @function
main:

Assembly and using readelf shows that they are only reordered but are in the same sections in the object file.