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UNW_GETCONTEXT(3)            Programming Library             UNW_GETCONTEXT(3)


NAME

       unw_getcontext -- get initial machine-state


SYNOPSIS

       #include <libunwind.h>

       int unw_getcontext(unw_context_t *ucp);


DESCRIPTION

       The unw_getcontext() routine initializes the context structure pointed
       to by ucp with the machine-state of the call-site. The exact set of
       registers stored by unw_getcontext() is platform-specific, but, in
       general, at least all preserved (``callee-saved'') and all
       frame-related registers, such as the stack-pointer, will be stored.

       This routine is normally implemented as a macro and applications should
       not attempt to take its address.

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


RETURN VALUE

       On successful completion, unw_getcontext() returns 0.  Otherwise, a
       value of -1 is returned.


THREAD AND SIGNAL SAFETY

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


SEE ALSO

       libunwind(3), unw_init_local(3)


AUTHOR

       David Mosberger-Tang
       Email: dmosberger@gmail.com
       WWW: http://www.nongnu.org/libunwind/.

Programming Library             16 August 2007               UNW_GETCONTEXT(3)

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