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Guard MODULO against the undefined INT_MIN % -1 (SIGFPE that kills the IOC) #38

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Guard MODULO against the undefined INT_MIN % -1 (SIGFPE that kills the IOC) #38

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17 changes: 14 additions & 3 deletions calcApp/src/aCalcPerform.c
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,17 @@
#define myMIN(a,b) (a)<(b)?(a):(b)
#define SMALL 1.e-9

/* Signed remainder that guards the one case C leaves undefined: INT_MIN % -1.
* On x86 the idiv used for '%' traps that quotient overflow as #DE, delivered
* as SIGFPE, killing the whole IOC. Mathematically x % -1 == 0 for every x, so
* return 0 for a -1 divisor instead of executing the trapping remainder. The
* divisor == 0 case is guarded separately at each call site. */
static long safeModulo(long a, long b)
{
if (b == -1) return 0;
return a % b;
}

static double local_random();
static int cond_search(const unsigned char **ppinst, int match);

Expand Down Expand Up @@ -647,7 +658,7 @@ long aCalcPerform(double *p_dArg, int num_dArgs, double **pp_aArg,
if ((int)ps1->a[i] == 0) {
ps->a[i] = myMAXFLOAT;
} else {
ps->a[i] = (double)((int)ps->a[i] % (int)ps1->a[i]);
ps->a[i] = (double)safeModulo((int)ps->a[i], (int)ps1->a[i]);
}
}
break;
Expand All @@ -671,7 +682,7 @@ long aCalcPerform(double *p_dArg, int num_dArgs, double **pp_aArg,
if ((int)ps1->d == 0) {
ps->a[i] = myMAXFLOAT;
} else {
ps->a[i] = (double)((int)ps->a[i] % (int)ps1->d);
ps->a[i] = (double)safeModulo((int)ps->a[i], (int)ps1->d);
}
}
break;
Expand All @@ -698,7 +709,7 @@ long aCalcPerform(double *p_dArg, int num_dArgs, double **pp_aArg,
if ((int)ps1->d == 0) {
ps->d = myMAXFLOAT;
} else {
ps->d = (double)((int)ps->d % (int)ps1->d);
ps->d = (double)safeModulo((int)ps->d, (int)ps1->d);
}
break;
}
Expand Down
16 changes: 14 additions & 2 deletions calcApp/src/sCalcPerform.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,18 @@ static int cond_search(const unsigned char **ppinst, int match);
#define myMIN(a,b) (a)<(b)?(a):(b)
#define SMALL 1.e-11

/* Signed remainder that guards the one case C leaves undefined: INT_MIN % -1
* (here also INT64_MIN % -1 on LP64). On x86 the idiv used for '%' traps that
* quotient overflow as #DE, delivered as SIGFPE, killing the whole IOC.
* Mathematically x % -1 == 0 for every x, so return 0 for a -1 divisor instead
* of executing the trapping remainder. The divisor == 0 case is guarded
* separately at each call site. */
static long safeModulo(long a, long b)
{
if (b == -1) return 0;
return a % b;
}

#define DEBUG 1
#define INIT_STACK 1
volatile int sCalcPerformDebug = 0;
Expand Down Expand Up @@ -559,7 +571,7 @@ epicsShareFunc long
--pd;
if ((int)(pd[1]) == 0)
return(-1);
*pd = (double)((int)(*pd) % (int)(pd[1]));
*pd = (double)safeModulo((int)(*pd), (int)(pd[1]));
break;

case REL_OR:
Expand Down Expand Up @@ -1106,7 +1118,7 @@ epicsShareFunc long
toDouble(ps);
if ((long)ps1->d == 0)
return(-1);
ps->d = (double)((long)ps->d % (long)ps1->d);
ps->d = (double)safeModulo((long)ps->d, (long)ps1->d);
break;

case REL_OR:
Expand Down