birgungelenbirgungider:D

Ilkin variant

void main(){

        int x=0;
        int y=x++;
        printf("x = %d and y = %d",x,y);
}

[root@picadapter ~]# ./test
x = 1 and y = 0

   0x0000000000400530 <+0>:     push   rbp
   0x0000000000400531 <+1>:     mov    rbp,rsp
   0x0000000000400534 <+4>:     sub    rsp,0x10
   0x0000000000400538 <+8>:     mov    DWORD PTR [rbp-0x4],0x0 < ====== 'x = 0'
   0x000000000040053f <+15>:    mov    eax,DWORD PTR [rbp-0x4]
   0x0000000000400542 <+18>:    lea    edx,[rax+0x1]
   0x0000000000400545 <+21>:    mov    DWORD PTR [rbp-0x4],edx
   0x0000000000400548 <+24>:    mov    DWORD PTR [rbp-0x8],eax
   0x000000000040054b <+27>:    mov    edx,DWORD PTR [rbp-0x8]
   0x000000000040054e <+30>:    mov    eax,DWORD PTR [rbp-0x4]
   0x0000000000400551 <+33>:    mov    esi,eax
   0x0000000000400553 <+35>:    mov    edi,0x400600
   0x0000000000400558 <+40>:    mov    eax,0x0
   0x000000000040055d <+45>:    call   0x400410 <printf@plt>
   0x0000000000400562 <+50>:    leave
   0x0000000000400563 <+51>:    ret


movement instruction ~~~~ int x = 0;
   0x0000000000400538 <+8>:     mov    DWORD PTR [rbp-0x4],0x0

(gdb) x/x $rbp-0x4
0x7fffffffe56c: 0x00000000

   0x000000000040053f <+15>:    mov    eax,DWORD PTR [rbp-0x4]
=> 0x0000000000400542 <+18>:    lea    edx,[rax+0x1]
rbp-0x4 = bu addressing modedan sonra adresdeki deyer yeni 0 movement edilir eax registerine
ardiyca lea (load effective address) rax registerinin uzerine yeni 0-in uzerine 1 deyerini gelir edx = rax+1; psuevdokod bu sekilde olur ve bu deyeri yeni 1i load edir edx registerine yeni x = 1; (x deyeri edx registeri olaraq istifade edilir). edx = 1; baxaq

(gdb) print /x $edx
$1 = 0x1
x = 1 :))
indi y deyerinin addresine baxaq
(gdb) x/x 0x7fffffffe56c
0x7fffffffe56c: 0x00000000
y deyerinin addressi helede 0-dir; hecbir deyishiklik yoxdur:)// increment operatorunun priority precedence-e sahib deyildi.


Kecek ikinci example-a
#include <stdio.h>
#include <string.h>


void main(){

        int x=0;
        int y=++x;
        printf("x = %d and y = %d",x,y);
}

[root@picadapter ~]# ./test
x = 1 and y = 1

   0x0000000000400538 <+8>:     mov    DWORD PTR [rbp-0x4],0x0
   0x000000000040053f <+15>:    add    DWORD PTR [rbp-0x4],0x1

yeniden baxaq demeli rbp-0x4 direktivi ile addresslenmis memory-e 0 deyeri teyin edilir.
0x0000000000400538 <+8>:     mov    DWORD PTR [rbp-0x4],0x0
(gdb) x/x $rbp-0x4 (bu address y deyiseninin adresidir)
0x7fffffffe56c: 0x00000000
ardiyca y adresine
add    DWORD PTR [rbp-0x4],0x1 ;bu instruction vasitesi ile o addressdeki deyere yeni 0-a +1 elave edilir;
burda y deyiseninin deyeri olur 1 baxaq;
(gdb) x/x $rbp-0x4
0x7fffffffe56c: 0x00000001 < === y = 1;
kecek x deyiseninin adresine ; daha sonra

   0x0000000000400543 <+19>:    mov    eax,DWORD PTR [rbp-0x4] < ==== 1 deyeri elave edilir eax registerine
=> 0x0000000000400546 <+22>:    mov    DWORD PTR [rbp-0x8],eax < ==== bu eax deyeri yeni 1 yerlesdirilir x deyiseninin adresine ardiyca x deyeride olur 1;

(gdb) x/x $rbp-0x8
0x7fffffffe568: 0x00000000 < === x deyiseni hal hazirda 0di mov    DWORD PTR [rbp-0x8],eax bu direktivden sonra 1 deyerini alacaq.
(gdb) x/x $rbp-0x8
0x7fffffffe568: 0x00000001

bu halda x ve y 1 deyerini alir cunki burd ++rax increment operatorunun precedence prioriteti movcuddur. Ona gorede birbasa 2 memory addressede effektiv addressleme ede bilir.