unw_get_reg(3)

1UNW_GET_REG(3)               Programming Library                UNW_GET_REG(3)
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NAME

6       unw_get_reg -- get register contents
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SYNOPSIS

9       #include <libunwind.h>
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11       int unw_get_reg(unw_cursor_t *cp, unw_regnum_t reg, unw_word_t *valp);
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DESCRIPTION

14       The  unw_get_reg() routine reads the value of register reg in the stack
15       frame identified by cursor cp and stores the value in the word  pointed
16       to by valp.
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18       The  register  numbering  is target-dependent and described in separate
19       manual pages (e.g., libunwind-ia64(3) for the IA-64 target).   Further‐
20       more,  the  exact set of accessible registers may depend on the type of
21       frame that cp is referring to. For ordinary stack frames,  it  is  nor‐
22       mally  possible  to access only the preserved (``callee-saved'') regis‐
23       ters and frame-related registers (such as the stack-pointer).  However,
24       for  signal frames (see unw_is_signal_frame(3)), it is usually possible
25       to access all registers.
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27       Note that unw_get_reg() can only read the contents of  registers  whose
28       values  fit  in  a  single word. See unw_get_fpreg(3) for a way to read
29       registers which do not fit this constraint.
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RETURN VALUE

32       On successful completion, unw_get_reg() returns 0.  Otherwise the nega‐
33       tive value of one of the error-codes below is returned.
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THREAD AND SIGNAL SAFETY

36       unw_get_reg()  is thread-safe as well as safe to use from a signal han‐
37       dler.
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ERRORS

40       UNW_EUNSPEC
41               An unspecified error occurred.
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43       UNW_EBADREG
44               An attempt was made to read a register that is  either  invalid
45              or not accessible in the current frame.
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47       In  addition,  unw_get_reg()  may  return  any  error  returned  by the
48       access_mem(), access_reg(), and access_fpreg() call-backs (see unw_cre‐
49       ate_addr_space(3)).
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AUTHOR

56       David Mosberger-Tang
57       Email: dmosberger@gmail.com
58       WWW: http://www.nongnu.org/libunwind/.
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62Programming Library             16 August 2007                  UNW_GET_REG(3)