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cxcodeqsortprogramming-pearls

"Programming Pearls": conflicting types for qsort

This is the solution of Programming Pearls in column 1.6_1:

> #include <stdio.h>

int intcomp(int *x, int *y)
{
    return *x-*y;
}
int a[1000000];
int main(void) {
    // insert code here...
    int i,n=0;
    while (scanf("%d",&a[n])!=EOF) {
        n++;
    }
    qsort(a,n,sizeof(a[0]),intcomp);
    for(i=0;i<n;i++)
    {
        printf("%d\n",a[i]);
    }
    return 0;
}

Error message:

conflicting types for "qsort"

Can you tell me why could that happen? Isn't it defined by default?

My compiler is Xcode (MacOS).

Solution

  • Comment (which turned out to be a correct guess) promoted to answer:

    It's unclear if the source code above was from typed in from the book, or found online. The code above has a few differences from this github copy of p1c1quicksort, i.e. the code above is missing:

    #include <stdlib.h>.