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24.\" $FreeBSD: head/lib/libc/stdlib/set_constraint_handler_s.3 338051 2018-08-19 14:39:57Z kib $
25.\"
26.Dd September 9, 2019
27.Dt SET_CONSTRAINT_HANDLER_S 3
28.Os
29.Sh NAME
30.Nm set_constraint_handler_s ,
31.Nm abort_handler_s ,
32.Nm ignore_handler_s
33.Nd runtime-constraint violation handling
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.Fd #define __STDC_WANT_LIB_EXT1__ 1
38.In stdlib.h
39.Ft constraint_handler_t
40.Fo set_constraint_handler_s
41.Fa "constraint_handler_t handler"
42.Fc
43.Ss Handler Prototype
44.Ft typedef void
45.Fo (*constraint_handler_t)
46.Fa "const char * restrict msg"
47.Fa "void * restrict ptr"
48.Fa "errno_t error"
49.Fc
50.Ss Predefined Handlers
51.Ft void
52.Fo abort_handler_s
53.Fa "const char * restrict msg"
54.Fa "void * restrict ptr"
55.Fa "errno_t error"
56.Fc
57.Ft void
58.Fo ignore_handler_s
59.Fa "const char * restrict msg"
60.Fa "void * restrict ptr"
61.Fa "errno_t error"
62.Fc
63.Sh DESCRIPTION
64The
65.Fn set_constraint_handler_s
66function sets the runtime-constraint violation handler to be
67.Fa handler .
68.Pp
69The runtime-constraint handler is the callback function invoked when a library
70function detects a runtime-constraint violation.
71.Pp
72The arguments are as follows:
73.Bl -tag -width "error"
74.It Fa msg
75A pointer to a character string describing the runtime-constraint violation.
76.It Fa ptr
77A
78.Dv NULL
79pointer.
80.It Fa error
81If the function calling the handler has a return type declared as
82.Vt errno_t ,
83the return value of the function is passed.
84Otherwise, a positive value of type
85.Vt errno_t
86is passed.
87.El
88.Pp
89Only the most recent handler registered with
90.Fn set_constraint_handler_s
91is called when a runtime-constraint violation occurs.
92.Pp
93The implementation has a default constraint handler that is used if no calls to
94the
95.Fn set_constraint_handler_s
96function have been made.
97If the
98.Fa handler
99argument to
100.Fn set_constraint_handler_s
101is a
102.Dv NULL
103pointer, the default handler becomes the current constraint handler.
104.Pp
105The
106.Fn abort_handler_s
107and
108.Fn ignore_handler_s
109are the standard-defined runtime-constraint handlers provided by the C library.
110.Pp
111The
112.Fn abort_handler_s
113function writes the error message including the
114.Fa msg
115to
116.Dv stderr
117and calls the
118.Xr abort 3
119function.
120The
121.Fn abort_handler_s
122is currently the default runtime-constraint handler.
123.Pp
124The
125.Fn ignore_handler_s
126simply returns to its caller.
127.Sh RETURN VALUES
128The
129.Fn set_constraint_handler_s
130function returns a pointer to the previously registered handler, or
131.Dv NULL
132if none was previously registered.
133.Pp
134The
135.Fn abort_handler_s
136function does not return to its caller.
137.Pp
138The
139.Fn ignore_handler_s
140function returns no value.
141.Sh STANDARDS
142The
143.Fn set_constraint_handler_s
144function conforms to
145.St -isoC-2011
146K.3.6.1.1.
147.Sh AUTHORS
148This manual page was written by
149.An Yuri Pankov Aq Mt yuripv@yuripv.net .
150