unw_set_reg - Man Page

set register contents


#include <libunwind.h>

int unw_set_reg(unw_cursor_t *cp, unw_regnum_t reg, unw_word_t val);


The unw_set_reg() routine sets the value of register  reg in the stack frame identified by cursor cp to the  value passed in val.

The register numbering is target-dependent and described in separate  manual pages (e.g., libunwind-ia64(3) for the IA-64 target).  Furthermore, the exact set of accessible registers may depend on the  type of frame that cp is referring to. For ordinary stack  frames, it is normally possible to access only the preserved  (“callee-saved”) registers and frame-related registers (such as the  stack-pointer). However, for signal frames (see  unw_is_signal_frame(3)), it is usually possible to access  all registers.

Note that unw_set_reg() can only write the contents of  registers whose values fit in a single word. See  unw_set_fpreg(3) for a way to write registers which do not  fit this constraint.

Return Value

On successful completion, unw_set_reg() returns 0.  Otherwise the negative value of one of the error-codes below is  returned.

Thread and Signal Safety

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



An unspecified error occurred.


An attempt was made to write a register  that is either invalid or not accessible in the current frame.


An attempt was made to write to a  read-only register.

In addition, unw_set_reg() may return any error returned by  the access_mem(), access_reg(), and  access_fpreg() call-backs (see  unw_create_addr_space(3)).

See Also

libunwind(3), libunwind-ia64(3), unw_get_reg(3), unw_is_signal_frame(3), unw_set_fpreg(3)


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

Referenced By

libunwind(3), unw_get_reg(3), unw_is_fpreg(3), unw_is_signal_frame(3), unw_resume(3), unw_set_fpreg(3).

16 August 2007 Programming Library