.data segment

.data segment

[ratheesh kannoth]

Hi List,

When I compiled (gcc -O0 -g  --no-pic -S  -fverbose-asm -c  2.c  -o
2.s) below  program to assembly code, it showed an uninitialized
static variable, "sta_char_unini" section.
 But when we execute the program, I can see that  "sta_char_unini" is
in .data section (thru /proc/<pid>/maps). What is wrong in my analysis
of 2.s ?

===================   2.c ==================================
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>

static char sta_char_unini;
static char sta_char_ini = 'B';

char char_unini;
char char_ini = '6';

int main()
{

        sta_char_unini = 5;

        char str1[] = "Hello world";
        char *str2  = "How are you";
        printf("Pid = %u\n", getpid());

        printf("sta_char_unini=%p sta_char_ini=%p\n", &sta_char_unini,
&sta_char_ini);

        while (1);

        return 0;
}

=================================== 2.s ===================

        .file   "2.c"
        .text
.Ltext0:
        .local  sta_char_unini
        .comm   sta_char_unini,1,1
        .data
        .type   sta_char_ini, @object
        .size   sta_char_ini, 1
sta_char_ini:
        .byte   66
        .comm   char_unini,1,1
        .globl  char_ini
        .type   char_ini, @object
        .size   char_ini, 1
char_ini:
        .byte   54
        .section        .rodata
.LC0:
        .string "How are you"
.LC1:
        .string "Pid = %u\n"
        .align 8
.LC2:
        .string "sta_char_unini=%p sta_char_ini=%p\n"
        .text
        .globl  main
        .type   main, @function
main:
.LFB0:
        .file 1 "2.c"
        .loc 1 12 1
        .cfi_startproc
......................................
........................................

Re: .data segment

[ratheesh kannoth]

i mean  -> when i analyze 2.s, uninitialized static variable,
"sta_char_unini" is in  .text section. But i expected it to be in
.data section.

On Fri, Jan 20, 2023 at 2:50 PM ratheesh kannoth <ratheesh.ksz@gmail.com> wrote:
>
> Hi List,
>
> When I compiled (gcc -O0 -g  --no-pic -S  -fverbose-asm -c  2.c  -o
> 2.s) below  program to assembly code, it showed an uninitialized
> static variable, "sta_char_unini" section.
>  But when we execute the program, I can see that  "sta_char_unini" is
> in .data section (thru /proc/<pid>/maps). What is wrong in my analysis
> of 2.s ?
>
> ===================   2.c ==================================
> #include <stdio.h>
> #include <stdint.h>
> #include <unistd.h>
>
> static char sta_char_unini;
> static char sta_char_ini = 'B';
>
> char char_unini;
> char char_ini = '6';
>
> int main()
> {
>
>         sta_char_unini = 5;
>
>         char str1[] = "Hello world";
>         char *str2  = "How are you";
>         printf("Pid = %u\n", getpid());
>
>         printf("sta_char_unini=%p sta_char_ini=%p\n", &sta_char_unini,
> &sta_char_ini);
>
>         while (1);
>
>         return 0;
> }
>
> =================================== 2.s ===================
>
>         .file   "2.c"
>         .text
> .Ltext0:
>         .local  sta_char_unini
>         .comm   sta_char_unini,1,1
>         .data
>         .type   sta_char_ini, @object
>         .size   sta_char_ini, 1
> sta_char_ini:
>         .byte   66
>         .comm   char_unini,1,1
>         .globl  char_ini
>         .type   char_ini, @object
>         .size   char_ini, 1
> char_ini:
>         .byte   54
>         .section        .rodata
> .LC0:
>         .string "How are you"
> .LC1:
>         .string "Pid = %u\n"
>         .align 8
> .LC2:
>         .string "sta_char_unini=%p sta_char_ini=%p\n"
>         .text
>         .globl  main
>         .type   main, @function
> main:
> .LFB0:
>         .file 1 "2.c"
>         .loc 1 12 1
>         .cfi_startproc
> ......................................
> ........................................