Re: [Mspgcc-users] Struct assignment BUG...

[Oleg Skydan]

Dear Roberto,

The swap function exchanges the contents of the two structs,
pointed by elements of the array v, so there a significant BUG.

I have omitted the initialization section for simplicity (I have found this BUG 
in 
a real program, which is very large).

Anyway the stack pointer should point to the same location at the function 
exit and entry (unless it is explicitly changed, using asm statement for 
example).

Thanks,
Oleg.
  ----- Original Message ----- 
  From: Roberto G. Berner 
  To: mspgcc-users@lists.sourceforge.net 
  Sent: Wednesday, January 22, 2003 6:25 PM
  Subject: RE: [Mspgcc-users] Struct assignment BUG...


  Dear Oleg:

  I think that there is no bug. Should I suggest trying ...

  struct x *tmp;


  Kind regards,

  Roberto G. Berner
  booleangene...@ciudad.com.ar
  ven...@increible.homelinux.com
  4308 3500 tel
  4308 3700 fax
  15 5122 6095 cel

    ----- Original Message ----- 
    From: Oleg Skydan 
    To: MSP430 GCC 
    Sent: Wednesday, January 22, 2003 12:12 PM
    Subject: [Mspgcc-users] Struct assignment BUG...


    Hello, All !

    I found a significant BUG when using struct assignment.

    Here is the sample:

    struct x{
    int a,b,c,d;
    };

    struct x *v[2];

    void swap(void)
    {
    struct x tmp;
     tmp=*v[0];
     *v[0]=*v[1];
     *v[1]=tmp;
    }

    And here is GCC's listing (with -O option):

    /***********************
     * Function `swap' 
     ***********************/
    swap:
    /* prologue: frame size = 8 */
    .L__FrameSize_swap=0x8
    .L__FrameOffset_swap=0x8
     sub #8, r1 ; 8, fpn 0
    /* prologue end (size=1) */
     mov &v, r15 
     mov @r15+, @r1
     mov @r15+, 2(r1)
     mov @r15+, 4(r1)
     mov @r15+, 6(r1)
     mov &v+2, r14 
     mov @r14+, 0(r15)
     mov @r14+, 2(r15)
     mov @r14+, 4(r15)
     mov @r14+, 6(r15)
     mov &v+2, r15 
     mov @r1+, 0(r15)       ;We should not change the stack pointer here !
     mov @r1+, 2(r15)
     mov @r1+, 4(r15)
     mov @r1+, 6(r15)
    /* epilogue: frame size=8 */
     add #8, r1                    ;After this command the stack pointer points 
to the illegal location !
     ret
    /* epilogue end (size=2) */
    /* function swap size 33 (30) */


    I use win32 version (from 10.12.2002).
    Thanks, Oleg.