从不兼容的指针类型传递'qsort'的参数4 [英] passing argument 4 of 'qsort' from incompatible pointer type
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问题描述
我在编写我们应该编写的函数时遇到了麻烦.据说这是应该如何工作的，但是它给了我不兼容的指针类型错误，而且我不确定如何解决它.
I'm having some trouble with a function we are supposed to be writing. Supposedly, this is how it should work, but it's giving me the incompatible pointer type error and I'm not sure how to fix it.
问题出在qsort上，它引用了compare_last函数.
The issue is in the qsort referencing the compare_last function.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_PERSONS 100
//person structure definition goes here
typedef struct{
char last[32];
char first[32];
int year;
}Person;
//function declarations go here
int compare_last(Person * ptr1, Person * ptr2);
void main(void){//main function goes here
char *infilename[20];
char *outfilename[20];
FILE * fptrin;
FILE * fptrout;
int i, j;
Person musicians[MAX_PERSONS];
printf("Enter input file name: ");
scanf("%s", infilename);
printf("Enter output file name: ");
scanf("%s", outfilename);
strcat(*outfilename, ".htm");
fptrin = fopen(*infilename, "r");
fptrout = fopen(*outfilename, "w");
for(i = 0; i < MAX_PERSONS; i++)
{
fscanf(fptrin, "%s %s %i", musicians[i].last, musicians[i].first, &musicians[i].year);
}
qsort(musicians, i, sizeof(musicians[0]), compare_last);
fprintf(fptrout, "<html>\n<body>\n<title>LAB14</title>\n");
for(j = 0; j < i; j++)
{
fprintf(fptrout, "%s %s %i <br>", musicians[j].last, musicians[j].first, musicians[j].year);
}
fprintf(fptrout, "</body>\n</html>\n");
fclose(fptrin);
fclose(fptrout);
}//end main
//function definitions go here
int compare_last(Person * ptr1, Person * ptr2)
{
int result = strcmp(ptr1 -> last, ptr2 -> last);
if(result != 0)
return result;
else
return strcmp(ptr1 -> first, ptr2 -> first);
}
推荐答案
int compare_last(Person * ptr1, Person * ptr2);
应该是
int compare_last(void * ptr1, void * ptr2);
然后您需要在compare_last
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