Difference between revisions of "c/algorithm/qsort"
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Revision as of 00:10, 1 September 2019
| Defined in header <stdlib.h>
|
||
| (1) | ||
| errno_t qsort_s( void *ptr, rsize_t count, rsize_t size, int (*comp)(const void *, const void *, void *), |
(2) | (since C11) |
ptr in ascending order. The array contains count elements of size bytes. Function pointed to by comp is used for object comparison. context is passed to comp and that the following errors are detected at runtime and call the currently installed constraint handler function:
-
countorsizeis greater than RSIZE_MAX -
ptrorcompis a null pointer (unlesscountis zero)
-
- As with all bounds-checked functions,
qsort_sis only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including <stdlib.h>.
If comp indicates two elements as equivalent, their order in the resulting sorted array is unspecified.
Parameters
| ptr | - | pointer to the array to sort |
| count | - | number of element in the array |
| size | - | size of each element in the array in bytes |
| comp | - | comparison function which returns a negative integer value if the first argument is less than the second, a positive integer value if the first argument is greater than the second and zero if the arguments are equivalent. The signature of the comparison function should be equivalent to the following: int cmp(const void *a, const void *b); The function must not modify the objects passed to it and must return consistent results when called for the same objects, regardless of their positions in the array. |
| context | - | additional information (e.g., collating sequence), passed to comp as the third argument
|
Return value
Notes
Despite the name, neither C nor POSIX standards require this function to be implemented using quicksort or make any complexity or stability guarantees.
Unlike other bounds-checked functions, qsort_s does not treat arrays of zero size as a runtime constraint violation and instead returns successfully without altering the array (the other function that accepts arrays of zero size is bsearch_s).
Until qsort_s, users of qsort often used global variables to pass additional context to the comparison function.
