Question

I’ve been Googling this for hours, but with no luck.

I’m using standard c, calling a very simple method, and returning the correct value, but after the return the value is completely wrong.

call:

     //declare the gross and ficaTax variables
    double gross;
    double ficaTax;

    //calculate the gross and the ficaTax
    gross = calcGross(payRate, hours); printf("%f\n", gross); //DELETE

Method:

double calcGross(double rate, double hours){

    double gross;

    //if the person didn't work more than 40 hours  
    if(hours <= 40.0){
            gross = hours * rate;
    }

    //if the person did work more than 40 hours
    else{
            gross = 40.0 * rate + ((hours - 40.0) * rate * 1.5);
    }

    printf("%f \t", gross);
    return gross;
}

I’m printing out the values in and out of the method to try and solve it, but I can’t figure it out. Here is the output:

(correct) (incorrect, after return)

529.600000 , -858993459.000000

1371.522500 , 171798692.000000

100.000000 , 0.000000

1515.710000 , 171798692.000000

977.255000 , 1030792150.000000

5631.360000 , 687194767.000000

7502.400000 , 1717986918.000000

4335.106000 , 584115553.000000

1924.181500 , -618475291.000000

683.084000 , 137438953.000000

1348.424000 , 755914245.000000

1369.200000 , -858993460.000000

529.600000 , -858993459.000000

4441.522500 , -1030792152.000000

100.000000 , 0.000000

1882.710000 , 171798692.000000

My only guesses were either that my double post-return was too long to fit in the length of a double, but I stored it in a double pre-return and it printed correctly. If this is the case I couldn’t figure out how to fix it.
My other guess was that I’m printing it out wrong post-return, but I am printing it the same way.

I’m using Linux and with the gcc compiler if that matters. Any help would be appreciated. I have been trying to fix this seemingly simple problem for hours.

Answer 1

The problem is that you haven’t given a declaration or prototype for the calcgross() function before it’s being called in your first example.

Without having seen a declaration/prototype for the function the C compiler will assume that it’s returning an int, not double, so things go terribly wrong.

Place the following line somewhere before you call the function (ideally in a header that you include):

double calcGross(double rate, double hours);

Using the -Wall compiler option would give you the following warning about this:

test.c:73:5: warning: implicit declaration of function 'calcGross' [-Wimplicit-function-declaration]