c/2588: Bad alignment when passing structure by value to function

[exco@ligim.univ-lyon1.fr]

>Number:         2588
>Category:       c
>Synopsis:       Bad alignment when passing structure by value to function
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 19 06:16:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Thierry EXCOFFIER
>Release:        gcc version 2.95.3 20010315 (release)
>Organization:
>Environment:
IRIX b710sibn 6.5 01101246 IP32
>Description:
For some structure size, when the structure is
passed by value to a function, its content is incorrect.

>How-To-Repeat:
/* The problem always appear when size D+F > 16 and F odd */

#define D 14
#define F 3

typedef struct
{
  int a[D] ;
} DoubleAlignment ;

typedef struct
{
  int a[F] ;
} FloatAlignment ;

void display(FloatAlignment x, DoubleAlignment y)
{
  int i ;
  
  for(i=0;i<F;i++)
    if ( x.a[i] != 100+i )
      printf("ERROR : x.a[%d] = %d != %d\n", i, x.a[i], 100+i) ;
  for(i=0;i<D;i++)
    if ( y.a[i] != 200+i )
      printf("ERROR : y.a[%d] = %d != %d\n", i, y.a[i], 200+i) ;
}

int main()
{
  FloatAlignment x ;
  DoubleAlignment y ;
  int i ;
  
  printf("D=%d F=%d\n", D, F) ;

  for(i=0;i<F;i++)
      x.a[i] = 100+i ;
  for(i=0;i<D;i++)
      y.a[i] = 200+i ;

  display(x, y) ;
  return(0) ;
}
>Fix:
Use -O3 option when compiling.
>Release-Note:
>Audit-Trail:
>Unformatted: