unw_getcontext(3)

1UNW_GETCONTEXT(3)            Programming Library             UNW_GETCONTEXT(3)
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NAME

6       unw_getcontext -- get initial machine-state
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SYNOPSIS

9       #include <libunwind.h>
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11       int unw_getcontext(unw_context_t *ucp);
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DESCRIPTION

14       The  unw_getcontext() routine initializes the context structure pointed
15       to by ucp with the machine-state of the call-site.  The  exact  set  of
16       registers stored by unw_getcontext() is platform-specific, but, in gen‐
17       eral, at least all preserved (``callee-saved'') and  all  frame-related
18       registers, such as the stack-pointer, will be stored.
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20       This routine is normally implemented as a macro and applications should
21       not attempt to take its address.
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PLATFORM-SPECIFIC NOTES

24       On IA-64, unw_context_t has a layout that is compatible  with  that  of
25       ucontext_t  and  such  structures  can be initialized with getcontext()
26       instead of unw_getcontext().  However, the reverse is not true  and  it
27       is not safe to use structures initialized by unw_getcontext() in places
28       where a structure initialized by getcontext() is expected.  The  reason
29       for  this  asymmetry  is that unw_getcontext() is optimized for maximum
30       performance and does not, for example, save the signal mask.
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RETURN VALUE

33       On successful completion, unw_getcontext()  returns  0.   Otherwise,  a
34       value of -1 is returned.
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THREAD AND SIGNAL SAFETY

37       unw_getcontext()  is  thread-safe  as well as safe to use from a signal
38       handler.
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AUTHOR

44       David Mosberger-Tang
45       Email: dmosberger@gmail.com
46       WWW: http://www.nongnu.org/libunwind/.
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50Programming Library             16 August 2007               UNW_GETCONTEXT(3)