Defined in header <stdlib.h>
void ignore_handler_s( const char * restrict msg,
                       void * restrict ptr,
                       errno_t error
(since C11)

The function simply returns to the caller without performing any other action.

A pointer to this function can be passed to set_constraint_handler_s to establish a runtime constraints violation handler that does nothing. As with all bounds-checked functions, ignore_handler_s is 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>.


msg - pointer to character string that describes the error
ptr - pointer to an implementation-defined object or a null pointer. Examples of implementation-defined objects are objects that give the name of the function that detected the violation and the line number when the violation was detected
error - the error about to be returned by the calling function, if it happens to be one of the functions that return errno_t

Return value



If ignore_handler_s is used as a the runtime constraints handler, the violations may be detected by examining the results of the bounds-checked function calls, which may be different for different functions (non-zero errno_t, null character written to the first byte of the output string, etc).

If set_constraint_handler_s is never called, the default handler is implementation-defined: it may be abort_handler_s, ignore_handler_s, or some other implementation-defined handler.


#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
#ifdef __STDC_LIB_EXT1__
    char dst[2];
    int r = strcpy_s(dst, sizeof dst, "Too long!");
    printf("dst = \"%s\", r = %d\n", dst, r);
    r = strcpy_s(dst, sizeof dst, "Too long!");
    printf("dst = \"%s\", r = %d\n", dst, r);

Possible output:

dst = "", r = 22
abort_handler_s was called in response to a runtime-constraint violation.
The runtime-constraint violation was caused by the following expression in strcpy_s:
(s1max <= (s2_len=strnlen_s(s2, s1max)) ) (in string_s.c:62)
Note to end users: This program was terminated as a result
of a bug present in the software. Please reach out to your
software's vendor to get more help.


  • C11 standard (ISO/IEC 9899:2011):
    • K. The ignore_handler_s function (p: 606)

See also

abort callback for the bounds-checked functions
set the error callback for bounds-checked functions

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