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Defined in header
constraint_handler_tset_constraint_handler_s(constraint_handler_thandler); (1) (since C11)typedefvoid(*constraint_handler_t)(constchar*restrictmsg,void*restrictptr,errno_terror); (2) (since C11)1) Configures the handler to be called by all
on a runtime constraint violation or restores the default handler (if handler is a null pointer).
2) The pointer to a handler that will be called on a runtime constraint violation.
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.
As with all bounds-checked functions, set_constraint_handler_s and constraint_handler_t are 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
.
Parameters
handler - pointer to function of type constraint_handler_t or a null pointer 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_tReturn value
A pointer to the previously-installed runtime constraints handler. (Note: this pointer is never a null pointer because calling set_constraint_handler_s(NULL) sets up the system default handler).
Example
Run this code
#define __STDC_WANT_LIB_EXT1__ 1#include<string.h>#include<stdio.h>#include<stdlib.h>intmain(void){#ifdef __STDC_LIB_EXT1__chardst[2];set_constraint_handler_s(ignore_handler_s);intr=strcpy_s(dst,sizeofdst,"Too long!");printf("dst = \"%s\", r = %d\n",dst,r);set_constraint_handler_s(abort_handler_s);r=strcpy_s(dst,sizeofdst,"Too long!");printf("dst = \"%s\", r = %d\n",dst,r);#endif}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. Aborted References
C23 standard (ISO/IEC 9899:2024):
K.3.6/2 constraint_handler_t (p: TBD)
K.3.6.1.1 The set_constraint_handler_s function (p: TBD)
C17 standard (ISO/IEC 9899:2018):
K.3.6/2 constraint_handler_t (p: TBD)
K.3.6.1.1 The set_constraint_handler_s function (p: TBD)
C11 standard (ISO/IEC 9899:2011):
K.3.6/2 constraint_handler_t (p: 604)
K.3.6.1.1 The set_constraint_handler_s function (p: 604-605)
See also