initializing at head of function or at some cases.

compilation.txt

# OS
Raspbian on Raspberry Pi 2

# gcc
$ gcc --version
gcc (Debian 4.6.3-14+rpi1) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc init_char.c

# objdump
$ objdump --version
GNU objdump (GNU Binutils for Debian) 2.24.51.20140425
Copyright (C) 2014 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) any later version.
This program has absolutely no warranty.

init_char.c

#include <stdio.h>

int init_at_case1(int type)
{
    switch(type){
    case 0:
        printf("nothing to do\n");
        break;
    case 1:
        {
            char buf[32] = {0};
            snprintf(buf, sizeof(buf)-1, "%d", 123);
            printf("%s\n",buf);
        }
        break;
    default:
        printf("default\n");
    }
    return 0;
}

int init_everytime(int type)
{
    char buf[32] = {0};
    switch(type){
    case 0:
        printf("nothing to do\n");
        break;
    case 1:
        {
            snprintf(buf, sizeof(buf)-1, "%d", 123);
            printf("%s\n",buf);
        }
        break;
    default:
        printf("default\n");
    }
    return 0;
}

int main(void)
{
    int i;
    for(i=0; i<3; i++){
        init_at_case1(i);
        init_everytime(i);
    }
    return 0;
}

objdump_init_at_case1.txt

00008400 <init_at_case1>:
    8400:   e92d4800    push    {fp, lr}
    8404:   e28db004    add fp, sp, #4
    8408:   e24dd028    sub sp, sp, #40 ; 0x28
    840c:   e50b0028    str r0, [fp, #-40]  ; 0x28
    8410:   e51b3028    ldr r3, [fp, #-40]  ; 0x28
    8414:   e3530000    cmp r3, #0
    8418:   0a000002    beq 8428 <init_at_case1+0x28>
    841c:   e3530001    cmp r3, #1
    8420:   0a000003    beq 8434 <init_at_case1+0x34>
    8424:   ea000026    b   84c4 <init_at_case1+0xc4>
    8428:   e59f00ac    ldr r0, [pc, #172]  ; 84dc <init_at_case1+0xdc>
    842c:   ebffffb9    bl  8318 <puts@plt>
    8430:   ea000025    b   84cc <init_at_case1+0xcc>
    8434:   e24b3024    sub r3, fp, #36 ; 0x24
    8438:   e3a02000    mov r2, #0
    843c:   e5832000    str r2, [r3]
    8440:   e2833004    add r3, r3, #4
    8444:   e3a02000    mov r2, #0
    8448:   e5832000    str r2, [r3]
    844c:   e2833004    add r3, r3, #4
    8450:   e3a02000    mov r2, #0
    8454:   e5832000    str r2, [r3]
    8458:   e2833004    add r3, r3, #4
    845c:   e3a02000    mov r2, #0
    8460:   e5832000    str r2, [r3]
    8464:   e2833004    add r3, r3, #4
    8468:   e3a02000    mov r2, #0
    846c:   e5832000    str r2, [r3]
    8470:   e2833004    add r3, r3, #4
    8474:   e3a02000    mov r2, #0
    8478:   e5832000    str r2, [r3]
    847c:   e2833004    add r3, r3, #4
    8480:   e3a02000    mov r2, #0
    8484:   e5832000    str r2, [r3]
    8488:   e2833004    add r3, r3, #4
    848c:   e3a02000    mov r2, #0
    8490:   e5832000    str r2, [r3]
    8494:   e2833004    add r3, r3, #4
    8498:   e59f3040    ldr r3, [pc, #64]   ; 84e0 <init_at_case1+0xe0>
    849c:   e24b2024    sub r2, fp, #36 ; 0x24
    84a0:   e1a00002    mov r0, r2
    84a4:   e3a0101f    mov r1, #31
    84a8:   e1a02003    mov r2, r3
    84ac:   e3a0307b    mov r3, #123    ; 0x7b
    84b0:   ebffffa1    bl  833c <snprintf@plt>
    84b4:   e24b3024    sub r3, fp, #36 ; 0x24
    84b8:   e1a00003    mov r0, r3
    84bc:   ebffff95    bl  8318 <puts@plt>
    84c0:   ea000001    b   84cc <init_at_case1+0xcc>
    84c4:   e59f0018    ldr r0, [pc, #24]   ; 84e4 <init_at_case1+0xe4>
    84c8:   ebffff92    bl  8318 <puts@plt>
    84cc:   e3a03000    mov r3, #0
    84d0:   e1a00003    mov r0, r3
    84d4:   e24bd004    sub sp, fp, #4
    84d8:   e8bd8800    pop {fp, pc}
    84dc:   00008690    .word   0x00008690
    84e0:   000086a0    .word   0x000086a0
    84e4:   000086a4    .word   0x000086a4

objdump_init_everytime.txt

000084e8 <init_everytime>:
    84e8:   e92d4800    push    {fp, lr}
    84ec:   e28db004    add fp, sp, #4
    84f0:   e24dd028    sub sp, sp, #40 ; 0x28
    84f4:   e50b0028    str r0, [fp, #-40]  ; 0x28
    84f8:   e24b3024    sub r3, fp, #36 ; 0x24
    84fc:   e3a02000    mov r2, #0
    8500:   e5832000    str r2, [r3]
    8504:   e2833004    add r3, r3, #4
    8508:   e3a02000    mov r2, #0
    850c:   e5832000    str r2, [r3]
    8510:   e2833004    add r3, r3, #4
    8514:   e3a02000    mov r2, #0
    8518:   e5832000    str r2, [r3]
    851c:   e2833004    add r3, r3, #4
    8520:   e3a02000    mov r2, #0
    8524:   e5832000    str r2, [r3]
    8528:   e2833004    add r3, r3, #4
    852c:   e3a02000    mov r2, #0
    8530:   e5832000    str r2, [r3]
    8534:   e2833004    add r3, r3, #4
    8538:   e3a02000    mov r2, #0
    853c:   e5832000    str r2, [r3]
    8540:   e2833004    add r3, r3, #4
    8544:   e3a02000    mov r2, #0
    8548:   e5832000    str r2, [r3]
    854c:   e2833004    add r3, r3, #4
    8550:   e3a02000    mov r2, #0
    8554:   e5832000    str r2, [r3]
    8558:   e2833004    add r3, r3, #4
    855c:   e51b3028    ldr r3, [fp, #-40]  ; 0x28
    8560:   e3530000    cmp r3, #0
    8564:   0a000002    beq 8574 <init_everytime+0x8c>
    8568:   e3530001    cmp r3, #1
    856c:   0a000003    beq 8580 <init_everytime+0x98>
    8570:   ea00000d    b   85ac <init_everytime+0xc4>
    8574:   e59f0048    ldr r0, [pc, #72]   ; 85c4 <init_everytime+0xdc>
    8578:   ebffff66    bl  8318 <puts@plt>
    857c:   ea00000c    b   85b4 <init_everytime+0xcc>
    8580:   e59f3040    ldr r3, [pc, #64]   ; 85c8 <init_everytime+0xe0>
    8584:   e24b2024    sub r2, fp, #36 ; 0x24
    8588:   e1a00002    mov r0, r2
    858c:   e3a0101f    mov r1, #31
    8590:   e1a02003    mov r2, r3
    8594:   e3a0307b    mov r3, #123    ; 0x7b
    8598:   ebffff67    bl  833c <snprintf@plt>
    859c:   e24b3024    sub r3, fp, #36 ; 0x24
    85a0:   e1a00003    mov r0, r3
    85a4:   ebffff5b    bl  8318 <puts@plt>
    85a8:   ea000001    b   85b4 <init_everytime+0xcc>
    85ac:   e59f0018    ldr r0, [pc, #24]   ; 85cc <init_everytime+0xe4>
    85b0:   ebffff58    bl  8318 <puts@plt>
    85b4:   e3a03000    mov r3, #0
    85b8:   e1a00003    mov r0, r3
    85bc:   e24bd004    sub sp, fp, #4
    85c0:   e8bd8800    pop {fp, pc}
    85c4:   00008690    .word   0x00008690
    85c8:   000086a0    .word   0x000086a0
    85cc:   000086a4    .word   0x000086a4