我找到了这个例子，但是当我收到编译警告时。如果有人可以帮助我，我会非常感激。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* qsort int comparison function */
int int_cmp(const void *a, const void *b)
{
const int *ia = (const int *)a; // casting pointer types
const int *ib = (const int *)b;
return *ia - *ib;
/* integer comparison: returns negative if b > a
and positive if a > b */
}
/* integer array printing function */
void print_int_array(const int *array, size_t len)
{
size_t i;
for(i=0; i<len; i++)
printf("%d | ", array[i]);
putchar('\n');
}
/* sorting integers using qsort() example */
void sort_integers_example()
{
int numbers[] = { 7, 3, 4, 1, -1, 23, 12, 43, 2, -4, 5 };
size_t numbers_len = sizeof(numbers)/sizeof(int);
puts("*** Integer sorting...");
/* print original integer array */
print_int_array(numbers, numbers_len);
/* sort array using qsort functions */
qsort(numbers, numbers_len, sizeof(int), int_cmp);
/* print sorted integer array */
print_int_array(numbers, numbers_len);
}
/* qsort C-string comparison function */
int cstring_cmp(const void *a, const void *b)
{
const char **ia = (const char **)a;
const char **ib = (const char **)b;
return strcmp(*ia, *ib);
/* strcmp functions works exactly as expected from
comparison function */
}
/* C-string array printing function */
void print_cstring_array(char **array, size_t len)
{
size_t i;
for(i=0; i<len; i++)
printf("%s | ", array[i]);
putchar('\n');
}
/* sorting C-strings array using qsort() example */
void sort_cstrings_example()
{
char *strings[] = { "Zorro", "Alex", "Celine", "Bill", "Forest", "Dexter" };
size_t strings_len = sizeof(strings) / sizeof(char *);
/** STRING */
puts("*** String sorting...");
/* print original string array */
print_cstring_array(strings, strings_len);
/* sort array using qsort functions */
qsort(strings, strings_len, sizeof(char *), cstring_cmp);
/* print sorted string array */
print_cstring_array(strings, strings_len);
}
/* an example of struct */
struct st_ex {
char product[16];
float price;
};
/* qsort struct comparision function (price float field) */
int struct_cmp_by_price(const void *a, const void *b)
{
struct st_ex *ia = (struct st_ex *)a;
struct st_ex *ib = (struct st_ex *)b;
return (int)(100.f*ia->price - 100.f*ib->price);
/* float comparison: returns negative if b > a
and positive if a > b. We multiplied result by 100.0
to preserve decimal fraction */
}
/* qsort struct comparision function (product C-string field) */
int struct_cmp_by_product(const void *a, const void *b)
{
struct st_ex *ia = (struct st_ex *)a;
struct st_ex *ib = (struct st_ex *)b;
return strcmp(ia->product, ib->product);
/* strcmp functions works exactly as expected from
comparison function */
}
/* Example struct array printing function */
void print_struct_array(struct st_ex *array, size_t len)
{
size_t i;
for(i=0; i<len; i++)
printf("[ product: %s \t price: $%.2f ]\n", array[i].product, array[i].price);
puts("--");
}
/* sorting structs using qsort() example */
void sort_structs_example(void)
{
struct st_ex structs[] = {{"mp3 player", 299.0f}, {"plasma tv", 2200.0f},
{"notebook", 1300.0f}, {"smartphone", 499.99f},
{"dvd player", 150.0f}, {"matches", 0.2f }};
size_t structs_len = sizeof(structs) / sizeof(struct st_ex);
puts("*** Struct sorting (price)...");
/* print original struct array */
print_struct_array(structs, structs_len);
/* sort array using qsort functions */
qsort(structs, structs_len, sizeof(struct st_ex), struct_cmp_by_price);
/* print sorted struct array */
print_struct_array(structs, structs_len);
puts("*** Struct sorting (product)...");
/* resort using other comparision function */
qsort(structs, structs_len, sizeof(struct st_ex), struct_cmp_by_product);
/* print sorted struct array */
print_struct_array(structs, structs_len);
}
/* MAIN program (calls all other examples) */
int main()
{
/* run all example functions */
sort_integers_example();
sort_cstrings_example();
sort_structs_example();
return 0;
}
/*
Execution result:
*** Integer sorting...
7 | 3 | 4 | 1 | -1 | 23 | 12 | 43 | 2 | -4 | 5 |
-4 | -1 | 1 | 2 | 3 | 4 | 5 | 7 | 12 | 23 | 43 |
*** String sorting...
Zorro | Alex | Celine | Bill | Forest | Dexter |
Alex | Bill | Celine | Dexter | Forest | Zorro |
*** Struct sorting (price)...
[ product: mp3 player price: $299.00 ]
[ product: plasma tv price: $2200.00 ]
[ product: notebook price: $1300.00 ]
[ product: smartphone price: $499.99 ]
[ product: dvd player price: $150.00 ]
[ product: matches price: $0.20 ]
--
[ product: matches price: $0.20 ]
[ product: dvd player price: $150.00 ]
[ product: mp3 player price: $299.00 ]
[ product: smartphone price: $499.99 ]
[ product: notebook price: $1300.00 ]
[ product: plasma tv price: $2200.00 ]
--
*** Struct sorting (product)...
[ product: dvd player price: $150.00 ]
[ product: matches price: $0.20 ]
[ product: mp3 player price: $299.00 ]
[ product: notebook price: $1300.00 ]
[ product: plasma tv price: $2200.00 ]
[ product: smartphone price: $499.99 ]
--
*/
我的错误如下：
g++ -Wall -o "Qiksortfromnet" "Qiksortfromnet.cpp" (in directory: /home/dylan)
Qiksortfromnet.cpp: In function ‘void sort_cstrings_example()’:
Qiksortfromnet.cpp:68:79: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
char *strings[] = { "Zorro", "Alex", "Celine", "Bill", "Forest", "Dexter" };
^
Qiksortfromnet.cpp:68:79: warning: deprecated conversion from string
constant to ‘char*’ [-Wwrite-strings] Qiksortfromnet.cpp:68:79:
warning: deprecated conversion from string constant to ‘char*’
[-Wwrite-strings] Qiksortfromnet.cpp:68:79: warning: deprecated
conversion from string constant to ‘char*’ [-Wwrite-strings]
Qiksortfromnet.cpp:68:79: warning: deprecated conversion from string
constant to ‘char*’ [-Wwrite-strings] Qiksortfromnet.cpp:68:79:
warning: deprecated conversion from string constant to ‘char*’
[-Wwrite-strings] Compilation finished successfully.
上次用户的上次修改删除了我的一半错误/警告...请不要这样做!!!
答案 0 :(得分：1)
换行：
或使用-Wno-write-strings