---
name: "unw_get_reg"
section: "3"
platform: "linux"
package: "libunwind"
version: "1.8.3-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/unw_get_reg"
---

# unw\_get\_reg(3)

## NAME

unw\_get\_reg -- get register contents

## SYNOPSIS

\#include \<libunwind.h\>\

int unw\_get\_reg(unw\_cursor\_t \*cp, unw\_regnum\_t reg, unw\_word\_t \*valp);\

## DESCRIPTION

The unw\_get\_reg() routine reads the value of register  reg in the stack frame identified by cursor cp and stores  the value in the word pointed to by valp.

The register numbering is target dependent and described in separate  manual pages (e.g., libunwind-ia64(3libunwind) 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(3libunwind)), it is usually possible to access  all registers.

Note that unw\_get\_reg() can only read the contents of  registers whose values fit in a single word. See  unw\_get\_fpreg(3libunwind) for a way to read registers which do not fit  this constraint.

## RETURN VALUE

On successful completion, unw\_get\_reg() returns 0.  Otherwise the negative value of one of the error codes below is  returned.

## THREAD AND SIGNAL SAFETY

unw\_get\_reg() is thread safe as well as safe to use  from a signal handler.

## ERRORS

- UNW\_EUNSPEC

   An unspecified error occurred.

- UNW\_EBADREG

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

In addition, unw\_get\_reg() may return any error returned by  the access\_mem(), access\_reg(), and  access\_fpreg() callbacks (see  unw\_create\_addr\_space(3libunwind)).

## SEE ALSO

libunwind(3libunwind), libunwind-ia64(3libunwind), unw\_get\_fpreg(3libunwind), unw\_is\_signal\_frame(3libunwind), unw\_set\_reg(3libunwind)

## AUTHOR

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