1 \documentclass{article} 2 \usepackage[fancyhdr,pdf]{latex2man} 3 4 \input{common.tex} 5 6 \begin{document} 7 8 \begin{Name}{3}{unw\_resume}{David Mosberger-Tang}{Programming Library}{unw\_resume}unw\_resume -- resume execution in a particular stack frame 9 \end{Name} 10 11 \section{Synopsis} 12 13 \File{\#include $<$libunwind.h$>$}\\ 14 15 \Type{int} \Func{unw\_resume}(\Type{unw\_cursor\_t~*}\Var{cp});\\ 16 17 \section{Description} 18 19 The \Func{unw\_resume}() routine resumes execution at the stack frame 20 identified by \Var{cp}. The behavior of this routine differs 21 slightly for local and remote unwinding. 22 23 For local unwinding, \Func{unw\_resume}() restores the machine state 24 and then directly resumes execution in the target stack frame. Thus 25 \Func{unw\_resume}() does not return in this case. Restoring the 26 machine state normally involves restoring the ``preserved'' 27 (callee-saved) registers. However, if execution in any of the stack 28 frames younger (more deeply nested) than the one identified by 29 \Var{cp} was interrupted by a signal, then \Func{unw\_resume}() will 30 restore all registers as well as the signal mask. Attempting to call 31 \Func{unw\_resume}() on a cursor which identifies the stack frame of 32 another thread results in undefined behavior (e.g., the program may 33 crash). 34 35 For remote unwinding, \Func{unw\_resume}() installs the machine state 36 identified by the cursor by calling the \Func{access\_reg} and 37 \Func{access\_fpreg} accessor callbacks as needed. Once that is 38 accomplished, the \Func{resume} accessor callback is invoked. The 39 \Func{unw\_resume} routine then returns normally (that is, unlikely 40 for local unwinding, \Func{unw\_resume} will always return for remote 41 unwinding). 42 43 Most platforms reserve some registers to pass arguments to exception 44 handlers (e.g., IA-64 uses \texttt{r15}-\texttt{r18} for this 45 purpose). These registers are normally treated like ``scratch'' 46 registers. However, if \Prog{libunwind} is used to set an exception 47 argument register to a particular value (e.g., via 48 \Func{unw\_set\_reg}()), then \Func{unw\_resume}() will install this 49 value as the contents of the register. In other words, the exception 50 handling arguments are installed even in cases where normally only the 51 ``preserved'' registers are restored. 52 53 Note that \Func{unw\_resume}() does \emph{not} invoke any unwind 54 handlers (aka, ``personality routines''). If a program needs this, it 55 will have to do so on its own by obtaining the \Type{unw\_proc\_info\_t} 56 of each unwound frame and appropriately processing its unwind handler 57 and language-specific data area (lsda). These steps are generally 58 dependent on the target-platform and are regulated by the 59 processor-specific ABI (application-binary interface). 60 61 \section{Return Value} 62 63 For local unwinding, \Func{unw\_resume}() does not return on success. 64 For remote unwinding, it returns 0 on success. On failure, the 65 negative value of one of the errors below is returned. 66 67 \section{Thread and Signal Safety} 68 69 \Func{unw\_resume}() is thread-safe. If cursor \Var{cp} is in the 70 local address-space, this routine is also safe to use from a signal 71 handler. 72 73 \section{Errors} 74 75 \begin{Description} 76 \item[\Const{UNW\_EUNSPEC}] An unspecified error occurred. 77 \item[\Const{UNW\_EBADREG}] A register needed by \Func{unw\_resume}() wasn't 78 accessible. 79 \item[\Const{UNW\_EINVALIDIP}] The instruction pointer identified by 80 \Var{cp} is not valid. 81 \item[\Const{UNW\_BADFRAME}] The stack frame identified by 82 \Var{cp} is not valid. 83 \end{Description} 84 85 \section{See Also} 86 87 \SeeAlso{libunwind(3)}, 88 \SeeAlso{unw\_set\_reg(3)}, 89 sigprocmask(2) 90 91 \section{Author} 92 93 \noindent 94 David Mosberger-Tang\\ 95 Email: \Email{dmosberger (a] gmail.com}\\ 96 WWW: \URL{http://www.nongnu.org/libunwind/}. 97 \LatexManEnd 98 99 \end{document} 100
