[LLVMbugs] [Bug 3455] New: another spurious divide by zero

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3455

           Summary: another spurious divide by zero
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: regehr at cs.utah.edu
                CC: llvmbugs at cs.uiuc.edu


At -O3, llvm-gcc r63488 on Ubuntu Hardy on x86 turns this program into one that
crashes via divide by zero.  If you look at the safe_div macro, it can be seen
that the divide is properly guarded.

#include <stdint.h>
#include <limits.h>

#define safe_div_macro_uint8_t_u_u(ui1,ui2) \
                ((((uint8_t)(ui2)) == ((uint8_t)0)) \
                        ? ((uint8_t)(ui1)) \
                        : (((uint8_t)(ui1)) / ((uint8_t)(ui2))))

static uint8_t
safe_div_func_uint8_t_u_u (uint8_t _ui1, uint8_t _ui2)
{
  return safe_div_macro_uint8_t_u_u(_ui1,_ui2);
}

#define safe_sub_macro_int64_t_s_s(si1,si2) \
                ((((((int64_t)(si1))^((int64_t)(si2))) \
                & (((((int64_t)(si1)) ^ ((((int64_t)(si1))^((int64_t)(si2))) \
                & (((int64_t)1) <<
(sizeof(int64_t)*CHAR_BIT-1))))-((int64_t)(si2)))^((int64_t)(si2)))) <
((int64_t)0)) \
                ? ((int64_t)(si1)) \
                : (((int64_t)(si1)) - ((int64_t)(si2))) \
                )

static int64_t
safe_sub_func_int64_t_s_s (int64_t _si1, int64_t _si2)
{
  return safe_sub_macro_int64_t_s_s(_si1,_si2);
}

uint32_t g_62;
uint32_t g_116;

int32_t func_57 (uint8_t p_59, uint8_t p_60, uint8_t p_61);
int32_t func_57 (uint8_t p_59, uint8_t p_60, uint8_t p_61)
{
  p_59 = (g_62 & p_60) != p_60;
  if (safe_div_func_uint8_t_u_u (p_60, p_59))
    for (1; 1; 1)
      {
      }
  return 1;
}

void func_52 (void);
void func_52 (void)
{
  if (func_57 (1, 1 < (safe_sub_func_int64_t_s_s (g_116, 1)), 1))
    {
    }
}
int
main (void)
{
  func_52 ();
  return 0;
}


-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.