gen/backtrace.3

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  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