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	1	.\" Copyright (c) 2007 Apple Inc.
	2	.\" All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\" 3. Neither the name of Apple Inc. ("Apple") nor the names of its
	13	.\" contributors may be used to endorse or promote products derived from
	14	.\" this software without specific prior written permission.
	15	.\"
	16	.\" THIS SOFTWARE IS PROVIDED BY APPLE AND CONTRIBUTORS ``AS IS'' AND
	17	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	18	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	19	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	20	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	21	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	22	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	23	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	24	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	25	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	26	.\" SUCH DAMAGE.
	27	.\"
	28	.\"
	29	.Dd February 15, 2007
	30	.Dt backtrace 3
	31	.Os "Mac OS X"
	32	.Sh NAME
	33	.Nm backtrace ,
	34	.Nm backtrace_symbols ,
	35	.Nm backtrace_symbols_fd
	36	.Nd call stack backtrace and display functions
	37	.Sh SYNOPSIS
	38	.In execinfo.h
	39	.Ft int
	40	.Fo backtrace
	41	.Fa "void** array"
	42	.Fa "int size"
	43	.Fc
	44	.Ft char**
	45	.Fo backtrace_symbols
	46	.Fa "void* const* array"
	47	.Fa "int size"
	48	.Fc
	49	.Ft void
	50	.Fo backtrace_symbols_fd
	51	.Fa "void* const* array"
	52	.Fa "int size"
	53	.Fa "int fd"
	54	.Fc
	55	.Sh DESCRIPTION
	56	These routines provide a mechanism to examine the current thread's call stack.
	57	.Pp
	58	.Fn backtrace
	59	writes the function return addresses of the current call stack to the array of
	60	pointers referenced by
	61	.Fa array .
	62	At most,
	63	.Fa size
	64	pointers are written. The number of pointers actually written to
	65	.Fa array
	66	is returned.
	67	.Pp
	68	.Fn backtrace_symbols
	69	attempts to transform a call stack obtained by
	70	.Fn backtrace
	71	into an array of human-readable strings using
	72	.Fn dladdr .
	73	The array of strings returned has
	74	.Fa size
	75	elements. It is allocated using
	76	.Fn malloc
	77	and should be released using
	78	.Fn free .
	79	There is no need to free the individual strings in the array.
	80	.Pp
	81	.Fn backtrace_symbols_fd
	82	performs the same operation as
	83	.Fn backtrace_symbols ,
	84	but the resulting strings are immediately written to the file descriptor
	85	.Fa fd ,
	86	and are not returned.
	87	.Sh EXAMPLE
	88	.Pp
	89	#include <execinfo.h>
	90	#include <stdio.h>
	91	...
	92	void* callstack[128];
	93	int i, frames = backtrace(callstack, 128);
	94	char** strs = backtrace_symbols(callstack, frames);
	95	for (i = 0; i < frames; ++i) {
	96	printf("%s\\n", strs[i]);
	97	}
	98	free(strs);
	99	...
	100	.Pp
	101	.Sh HISTORY
	102	These functions first appeared in
	103	Mac OS X 10.5.
	104	.Sh SEE ALSO
	105	.Xr dladdr 3 ,
	106	.Xr malloc 3