Thread: conflicting data types

this won't compile

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define ALLOCSIZE 10000
#define MAXLINES 5000
#define MAXLEN 1000

char *lineptr[MAXLINES];
static char allocbuf[ALLOCSIZE];
static char *allocp = allocbuf;

void swap(void *v[], int i, int j);
int getline(char line[], int maxline);
char *alloc(int);
int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);

void qsort(void *lineptr[], int left, int right, int (*comp)(void *, void *));


int numcmp(char *s, char *t);

int strcmp(char *s, char *t){
    for ( ; *s == *t; s++, t++)
        if (*s == '\0')
            return 0;
    return *s - *t;
}


int main(int argc, char *argv[]){

    int nlines;
    int numeric = 0;

    if (argc>1 && strcmp(argv[1], "-n") == 0)
        numeric = 1;

    if( (nlines = readlines(lineptr, MAXLINES)) >= 0 ){
        qsort((void **)lineptr, 0, nlines-1, (int (*)(void *, void *))(numeric ? numcmp : strcmp));
        writelines(lineptr, nlines);
        return 0;
    } else {
        printf("input too big to sort\n");
        return -1;
    }
}

char *alloc(int n){
    if (allocbuf + ALLOCSIZE - allocp >= n){
        allocp += n;
        return allocp - n;
    } else {
        return 0;
    }
}

int getline(char s[],int lim)
{
    int c, i;
    for (i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
        s[i] = c;
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';
    return i;
}
void swap(void *v[], int i, int j){
    void *temp;
    temp = v[i];
    v[i] = v[j];
    v[j] = temp;
 }
int numcmp(char *s1, char *s2){
    double v1, v2;

    v1 = atof(s1);
    v2 = atof(s2);

    if (v1 < v2)
        return -1;
    else if(v1 > v2)
        return 1;
    else
        return 0;
}

void qsort(void *v[], int left, int right, int (*comp)(void *, void *)){
    int i, last;

    void swap(void *v[], int, int);
    if( left >= right )
        return;
    swap(v, left, (left+right)/2);
    last = left;
    for(i = left; i <= right; i++)
        if((*comp)(v[i], v[left]) < 0)
            swap(v, ++last, i);
    swap(v, left, last);
    qsort(v, left, last-1, comp);
    qsort(v, last+1, right, comp);
}


int readlines(char *lineptr[], int maxlines){
    int len, nlines;
    char *p, line[MAXLINES];

    nlines = 0;
    while( (len = getline(line, MAXLEN)) > 0 )
        if( nlines >= maxlines || (p = alloc(len)) == NULL )
            return -1;
        else {
            line[len-1] = '\0';
            strcpy(p, line);
            lineptr[nlines++] = p;
        }
    return nlines;
}

void writelines(char *lineptr[], int nlines){
    int i;
    for(i = 0; i < nlines; i++){
        printf("%s\n", lineptr[i]);
    }
}

it gives error thus

||=== Build: Debug in dbg (compiler: GNU GCC Compiler) ===|
C:\Users\goget\Documents\strcmp.c|20|error: conflicting types for 'qsort'|
C:\Program Files (x86)\CodeBlocks\MinGW\include\stdlib.h|371|note: previous declaration of 'qsort' was here|
C:\Users\goget\Documents\strcmp.c|25|error: conflicting types for 'strcmp'|
C:\Program Files (x86)\CodeBlocks\MinGW\include\string.h|43|note: previous declaration of 'strcmp' was here|
C:\Users\xx\Documents\strcmp.c||In function 'main':|
C:\Users\xx\Documents\strcmp.c|42|warning: passing argument 1 of 'qsort' from incompatible pointer type|
C:\Users\xx\Documents\strcmp.c|20|note: expected 'void **' but argument is of type 'char **'|
C:\Users\xx\Documents\strcmp.c|92|error: conflicting types for 'qsort'|
C:\Program Files (x86)\CodeBlocks\MinGW\include\stdlib.h|371|note: previous declaration of 'qsort' was here|
||=== Build failed: 3 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|

i understand that in the stdlib.h file, the declaration for qsort is

Code:

_CRTIMP void __cdecl qsort(void*, size_t, size_t,
               int (*)(const void*, const void*));

which means the first argument is a void pointer

but the one use in the book k&r is

Code:

void qsort(void *lineptr[], int left, int right, int (*comp)(void *, void *));

which is an array of void pointers and this is needed for the program. what can i do to make it compile?

2. Also, for strcmp function in string.h, the declaration is

Code:

_CRTIMP int __cdecl __MINGW_NOTHROW    strcmp (const char*, const char*)  __MINGW_ATTRIB_PURE;

but in the program in k&r its

Code:

int strcmp(char *s, char *t)

so why is the compiler saying incompatible type??

i'm confused sirs..