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

[Roberto G. Berner]

Dear Oleg:

Accept my apologies, but I think you should check this. If I am wrong, please 
excuse me.


struct x{                /* struct of type x defined */
int a,b,c,d;
};

struct x *v[2];    /* array of 2 pointers to structures of type x - somewhere 
initialized, OK ?*/

/* swap pointers, this means after call to swap(), v[0] holds the pointer to 
v[1] and viceversa */

void swap(void)    {
struct x tmp;    /*  this declaraction should be struct x *tmp , and not the 
variable tmp of type struct x !!! */
 tmp=*v[0];        /* tmp should be a pointer in order to hold pointers 
properly */
 *v[0]=*v[1];
 *v[1]=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: mspgcc-users@lists.sourceforge.net 
  Sent: Wednesday, January 22, 2003 4:27 PM
  Subject: Re: [Mspgcc-users] Struct assignment BUG...


  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.