Multiple errors on compiling quicksort program's code file in C, on Cygwin.

ajiten · 06-21-2023, 03:41 AM

Have the Quicksort program, in which had to implement only the main, cmp(comparator), & selectPivotIndex functions.
Rest program functions are copied from the book: Algorithms in a nutshell, by George T. Heineman.

Have built the following code, and compiled using the :

Code:

 gcc --save-temps --verbose quicksort.c -o  quicksort

Though, once the errors subside, will use the option:

Code:

 cc -pedantiC -W -Wall -Werror quicksort.c -o quicksort

Code:

#include<stdio.h>
int partition(void **, int, int *, int, int , int);
int cmp(const void *, const void*);
void do_qsort(void **, int *, int, int);
int selectPivotIndex(void **, int int);

int main(){
	void ** vals;//array of pointers
        int total_elements;
	return do_qsort(vals, total_elements-1, int(* cmp)(const void *, const void*));
}

void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
	int pivotIndex;
	if (right<= left) return;
        pivotIndex = selectPivotIndex(ar, left, right);
	pivotIndex = partition(ar, cmp, left, right, pivotIndex);
	do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
}

int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int PivotIndex){
       int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right]; 
       ar[right] = ar[pivotIndex];  ar[pivotIndex]= tmp;
       store = left;
       for(idx= left; idx<right;idx++){
	       if(cmp(ar[idx], pivot <=0){
	              tmp = ar[idx]; ar[idx]=ar[store]; ar[store]=tmp; store++;
	       }
       }
       tmp= ar[right];  ar[right] = ar[store];  ar[store] = tmp;

       return store;
}

int cmp(const void * a, const void *b)
{
      if ((int*)a<=(int*)b)  return 0;
      else return 1;
} 

int selectPivotIndex(void ** ar, int left, int right)
{
      int median;
      median = (left+right)/2;
      if(median %2==0) median = median +1;
      return median;
}

Have got many errors, as shown below:

Code:

quicksort.c: In function ‘main’:
quicksort.c:10:49: error: expected expression before ‘int’
   10 |         return do_qsort(vals, total_elements-1, int(* cmp)(const void *, const void*));
      |                                                 ^~~
quicksort.c:10:45: warning: passing argument 2 of ‘do_qsort’ makes pointer from integer without a cast [-Wint-conversion]
   10 |         return do_qsort(vals, total_elements-1, int(* cmp)(const void *, const void*));
      |                               ~~~~~~~~~~~~~~^~
      |                                             |
      |                                             int
quicksort.c:4:24: note: expected ‘int *’ but argument is of type ‘int’
    4 | void do_qsort(void **, int *, int, int);
      |                        ^~~~~
quicksort.c:10:16: error: too few arguments to function ‘do_qsort’
   10 |         return do_qsort(vals, total_elements-1, int(* cmp)(const void *, const void*));
      |                ^~~~~~~~
quicksort.c:4:6: note: declared here
    4 | void do_qsort(void **, int *, int, int);
      |      ^~~~~~~~
quicksort.c: At top level:
quicksort.c:13:90: error: redefinition of parameter ‘right’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |                                                                                      ~~~~^~~~~
quicksort.c:13:30: note: previous definition of ‘right’ with type ‘int’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |                          ~~~~^~~~~
quicksort.c:13:6: error: conflicting types for ‘do_qsort’; have ‘void(void **, int,  int (*)(const void *, const void *), int,  int)’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |      ^~~~~~~~
quicksort.c:4:6: note: previous declaration of ‘do_qsort’ with type ‘void(void **, int *, int,  int)’
    4 | void do_qsort(void **, int *, int, int);
      |      ^~~~~~~~
quicksort.c: In function ‘do_qsort’:
quicksort.c:17:36: warning: passing argument 2 of ‘partition’ makes integer from pointer without a cast [-Wint-conversion]
   17 |         pivotIndex = partition(ar, cmp, left, right, pivotIndex);
      |                                    ^~~
      |                                    |
      |                                    int (*)(const void *, const void *)
quicksort.c:2:24: note: expected ‘int’ but argument is of type ‘int (*)(const void *, const void *)’
    2 | int partition(void **, int, int *, int, int , int);
      |                        ^~~
quicksort.c:17:41: warning: passing argument 3 of ‘partition’ makes pointer from integer without a cast [-Wint-conversion]
   17 |         pivotIndex = partition(ar, cmp, left, right, pivotIndex);
      |                                         ^~~~
      |                                         |
      |                                         int
quicksort.c:2:29: note: expected ‘int *’ but argument is of type ‘int’
    2 | int partition(void **, int, int *, int, int , int);
      |                             ^~~~~
quicksort.c:17:22: error: too few arguments to function ‘partition’
   17 |         pivotIndex = partition(ar, cmp, left, right, pivotIndex);
      |                      ^~~~~~~~~
quicksort.c:2:5: note: declared here
    2 | int partition(void **, int, int *, int, int , int);
      |     ^~~~~~~~~
quicksort.c:18:22: warning: passing argument 2 of ‘do_qsort’ makes integer from pointer without a cast [-Wint-conversion]
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                      ^~~
      |                      |
      |                      int (*)(const void *, const void *)
quicksort.c:13:30: note: expected ‘int’ but argument is of type ‘int (*)(const void *, const void *)’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |                          ~~~~^~~~~
quicksort.c:18:27: warning: passing argument 3 of ‘do_qsort’ makes pointer from integer without a cast [-Wint-conversion]
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                           ^~~~
      |                           |
      |                           int
quicksort.c:13:42: note: expected ‘int (*)(const void *, const void *)’ but argument is of type ‘int’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |                                     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
quicksort.c:18:9: error: too few arguments to function ‘do_qsort’
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |         ^~~~~~~~
quicksort.c:13:6: note: declared here
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |      ^~~~~~~~
quicksort.c:18:66: error: ‘pivotInex’ undeclared (first use in this function); did you mean ‘pivotIndex’?
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                                                                  ^~~~~~~~~
      |                                                                  pivotIndex
quicksort.c:18:66: note: each undeclared identifier is reported only once for each function it appears in
quicksort.c:18:77: error: expected expression before ‘,’ token
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                                                                             ^
quicksort.c:18:61: warning: passing argument 2 of ‘do_qsort’ makes integer from pointer without a cast [-Wint-conversion]
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                                                             ^~~
      |                                                             |
      |                                                             int (*)(const void *, const void *)
quicksort.c:13:30: note: expected ‘int’ but argument is of type ‘int (*)(const void *, const void *)’
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |                          ~~~~^~~~~
quicksort.c:18:48: error: too few arguments to function ‘do_qsort’
   18 |         do_qsort(ar, cmp, left, pivotIndex-1);  do_qsort(ar, cmp, pivotInex+!, right);
      |                                                ^~~~~~~~
quicksort.c:13:6: note: declared here
   13 | void do_qsort(void **ar, int right, int(*cmp)(const void *, const void *), int left, int right){
      |      ^~~~~~~~
quicksort.c: At top level:
quicksort.c:21:5: error: conflicting types for ‘partition’; have ‘int(void **, int (*)(const void *, const void *), int,  int,  int)’
   21 | int partition(void ** ar, int(* cmp)(const void*, const void*), int left, int right, int PivotIndex){
      |     ^~~~~~~~~
quicksort.c:2:5: note: previous declaration of ‘partition’ with type ‘int(void **, int,  int *, int,  int,  int)’
    2 | int partition(void **, int, int *, int, int , int);
      |     ^~~~~~~~~
quicksort.c: In function ‘partition’:
quicksort.c:22:41: error: ‘pivotIndex’ undeclared (first use in this function); did you mean ‘PivotIndex’?
   22 |        int idx, store; void *pivot = ar[pivotIndex]; void *tmp = ar[right];
      |                                         ^~~~~~~~~~
      |                                         PivotIndex
quicksort.c:26:38: warning: passing argument 2 of ‘cmp’ makes pointer from integer without a cast [-Wint-conversion]
   26 |                if(cmp(ar[idx], pivot <=0){
      |                                ~~~~~~^~~
      |                                      |
      |                                      int
quicksort.c:26:38: note: expected ‘const void *’ but argument is of type ‘int’
quicksort.c:26:42: error: expected ‘)’ before ‘{’ token
   26 |                if(cmp(ar[idx], pivot <=0){
      |                  ~                       ^
      |                                          )
quicksort.c:29:8: error: expected expression before ‘}’ token
   29 |        }
      |        ^

pan64 · 06-21-2023, 06:03 AM

First of all you do not need to open a new thread for this.
Next, there is a typo here - a ) is missing:

Code:

if(cmp(ar[idx], pivot) <=0)

Your code is syntactically incorrect.
And I think that cmp should return -1, 0, 1, so your implementation is incorrect: https://www.geeksforgeeks.org/compar...of-qsort-in-c/