sigsetjmp(3) Library Functions Manual sigsetjmp(3)
NAME
sigsetjmp, siglongjmp - Saves and restores the current execution context
LIBRARY
Standard C Library (libc.a, libc.so)
SYNOPSIS
#include <setjmp.h>
int sigsetjmp(
sigjmp_buf environment ,
int savemask);
void siglongjmp(
sigjmp_buf environment,
int value);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
siglongjmp(), sigsetjmp(): XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies an address for a sigjmp_buf structure. Specifies whether the current signal mask should be saved. If this parameter contains a
0 (zero) value, sigsetjmp() does not save the signal mask. Otherwise, the function saves the signal mask. Specifies the value you want
written to the execution context as the return value of the sigsetjmp() function. If you specify 0 (zero) in this parameter, the execution
context contains a value of 1 as the sigsetjmp() return value. See the RETURN VALUES section for more information.
DESCRIPTION
The sigsetjmp() and siglongjmp() functions are useful when handling errors and interrupts encountered in low-level functions of a program.
The sigsetjmp() function saves the current stack context in the buffer specified by the environment parameter. If the value of the save-
mask parameter is not 0 (zero), the sigsetjmp() function also saves the process' current signal mask as part of the calling environment.
You use the buffer specified by the environment parameter in a later call to the siglongjmp() function. The siglongjmp() function restores
the stack context and (optionally) signal mask that were saved by the sigsetjmp() function.
After the siglongjmp() function runs, program execution continues as if the corresponding call to the sigsetjmp() function had just
returned the value of the value parameter. The function that called the sigsetjmp() function must not have returned before the completion
of the siglongjmp() function.
Because it bypasses the usual function call and return mechanisms, the siglongjmp() function executes correctly in contexts of interrupts,
signals, and any of their associated functions. However, if the siglongjmp() function is invoked from a nested signal handler (that is,
from a function invoked as a result of a signal raised during the handling of another signal), the behavior is undefined.
CAUTION
The results of the siglongjmp() function are undefined if one of the following is true: The siglongjmp() function is called with an envi-
ronment parameter that was not previously set by the sigsetjmp() function The function that made the corresponding call to the sigsetjmp()
function has already returned.
If the siglongjmp() function detects one of these conditions, it calls the longjmperror() function. If longjmperror() returns, the program
is aborted. The default version of longjmperror() displays an error message to standard error and returns. If you want your program to
exit more gracefully, you can write your own version of the longjmperror() program.
RETURN VALUES
After the siglongjmp() function is finished executing, program execution continues as if the corresponding call of the sigsetjmp() function
just returned. In other words, the execution context saved by the corresponding sigsetjmp() function is in place and execution continues
at the statement immediately following the call to the sigsetjmp() function.
Part of that execution context is the return value from the sigsetjmp() function. When the sigsetjmp() function actually returns (before
the call to the siglongjmp() function), that return value is 0 (zero). When the siglongjmp() function returns, the execution context con-
tains a non-zero value as the return value from the sigsetjmp() function.
The value you specify in the value parameter to the siglongjmp() function is written to the execution context as the return value for the
sigsetjmp() function. You cannot cause the execution context to contain a 0 (zero) value for the sigsetjmp() return value. If you specify
0 in the value parameter, the execution context contains a 1 as the sigsetjmp() return value.
RELATED INFORMATION
Routines: setjmp(3)
Standards: standards(5) delim off
sigsetjmp(3)