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24.Dd August 18, 2018
25.Dt SET_CONSTRAINT_HANDLER_S 3
26.Os
27.Sh NAME
28.Nm set_constraint_handler_s ,
29.Nm abort_handler_s ,
30.Nm ignore_handler_s
31.Nd runtime-constraint violation handling
32.Sh LIBRARY
33.Lb libc
34.Sh SYNOPSIS
35.Fd #define __STDC_WANT_LIB_EXT1__ 1
36.In stdlib.h
37.Ft constraint_handler_t
38.Fo set_constraint_handler_s
39.Fa "constraint_handler_t handler"
40.Fc
41.Ss Handler Prototype
42.Ft typedef void
43.Fo (*constraint_handler_t)
44.Fa "const char * restrict msg"
45.Fa "void * restrict ptr"
46.Fa "errno_t error"
47.Fc
48.Ss Predefined Handlers
49.Ft void
50.Fo abort_handler_s
51.Fa "const char * restrict msg"
52.Fa "void * restrict ptr"
53.Fa "errno_t error"
54.Fc
55.Ft void
56.Fo ignore_handler_s
57.Fa "const char * restrict msg"
58.Fa "void * restrict ptr"
59.Fa "errno_t error"
60.Fc
61.Sh DESCRIPTION
62The
63.Fn set_constraint_handler_s
64function sets the runtime-constraint violation handler to be
65.Fa handler .
66.Pp
67The runtime-constraint handler is the callback function invoked when a library
68function detects a runtime-constraint violation.
69.Pp
70The arguments are as follows:
71.Bl -tag -width "error"
72.It Fa msg
73A pointer to a character string describing the runtime-constraint violation.
74.It Fa ptr
75A
76.Dv NULL
77pointer.
78.It Fa error
79If the function calling the handler has a return type declared as
80.Vt errno_t ,
81the return value of the function is passed.
82Otherwise, a positive value of type
83.Vt errno_t
84is passed.
85.El
86.Pp
87Only the most recent handler registered with
88.Fn set_constraint_handler_s
89is called when a runtime-constraint violation occurs.
90.Pp
91The implementation has a default constraint handler that is used if no calls to
92the
93.Fn set_constraint_handler_s
94function have been made.
95If the
96.Fa handler
97argument to
98.Fn set_constraint_handler_s
99is a
100.Dv NULL
101pointer, the default handler becomes the current constraint handler.
102.Pp
103The
104.Fn abort_handler_s
105and
106.Fn ignore_handler_s
107are the standard-defined runtime-constraint handlers provided by the C library.
108.Pp
109The
110.Fn abort_handler_s
111function writes the error message including the
112.Fa msg
113to
114.Dv stderr
115and calls the
116.Xr abort 3
117function.
118The
119.Fn abort_handler_s
120is currently the default runtime-constraint handler.
121.Pp
122The
123.Fn ignore_handler_s
124simply returns to its caller.
125.Sh RETURN VALUES
126The
127.Fn set_constraint_handler_s
128function returns a pointer to the previously registered handler, or
129.Dv NULL
130if none was previously registered.
131.Pp
132The
133.Fn abort_handler_s
134function does not return to its caller.
135.Pp
136The
137.Fn ignore_handler_s
138function returns no value.
139.Sh STANDARDS
140The
141.Fn set_constraint_handler_s
142function conforms to
143.St -isoC-2011
144K.3.6.1.1.
145.Sh AUTHORS
146This manual page was written by
147.An Yuri Pankov Aq Mt yuripv@yuripv.net .
148