double pop(void)
{
    if(sp > 0)
        return val[--sp];
    else {
        printf("error: stack emptyn");
        return 0.0;
    }
}

int pop(double* outval)
{
        if(outval == 0) return -1;
        if(sp > 0)
                *outval = val[--sp];
        else {
                printf("error: stack emptyn");
                return -1;
        }
        return 0;
}

TRY {
    ...
    THROW(MY_EXCEPTION);
    /* Unreachable */
  } CATCH(MY_EXCEPTION) {
    ...
  } CATCH(OTHER_EXCEPTION) {
    ...
  } FINALLY {
    ...
  }

int pop(double *dptr)
{
    if(sp > 0) {
            *dptr = val[--sp];
            return 0;
    } else {
            return 1;
    }
}

double pop(int *error)
{
  if(sp > 0) {
      return val[--sp];
      *error = 0;
  } else {
     *error = 1;
      printf("error: stack emptyn");
      return 0.0;
  }

int pop(double *d)
{
   if(sp > 0) {
       *d = val[--sp];
       return 0;
   } else {
     return 1;

   }
}

struct stack{
    double* pData;
    uint32  size;
};

struct popRC{
    double value;
    uint32 size_before_pop;
};

popRC pop(struct stack* pS){
    popRC rc;
    rc.size=pS->size;
    if(rc.size){
        --pS->size;
        rc.value=pS->pData[pS->size];
    }
    return rc;
}

popRC rc = pop(&stack);
if(rc.size_before_pop!=0){
    ....use rc.value

std::pair<something,bool>

std::set<...>::insert
std::map<...>::insert

enum{FAIL,SUCCESS};

int empty(struct stack* pS){
    return (pS->size == 0) ? 1 : 0;
}

int ok=0;

do
{
   /* Do stuff here */

   /* If there is an error */
   break;

   /* If we got to the end without an error */
   ok=1;

} while(0);

if (ok == 0)
{
   printf("Fail.n");
}
else
{
   printf("Ok.n");
}