sigaltstack - set or get signal alternate stack context
int sigaltstack( const stack_t *ss, stack_t *oss );
The following function declaration does not conform to current standards and is supported only for backward compatibility: #include <signal.h>
Interfaces documented on this reference page conform to industry standards as follows:
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If valid, specifies a pointer to a structure that indicates
what will be in effect upon return from the call to the
If not NULL, specifies the pointer to a structure that contains
the alternate signal stack that was in effect prior to the call to the
This function enables another stack area to be defined where signals can be examined for their execution status and processed. If a signal's action, specified by the sigaction(2) function, indicates that a signal should execute on an alternate stack, that signal is examined for its processing status. A process that is not currently executing on the signal stack is switched to an alternate stack for the duration of the handler's execution.
The sigaltstack structure is set up as follows:
void *ss_sp /* SVID3 uses caddr_t ss_sp int ss_flags size_t ss_size
The values for the fields are: Signal stack pointer. Specifies the new stack state and may be set to either SS_DISABLE or SS_ONSTACK as follows: If ss is not NULL, the new state may be set to SS_DISABLE, which specifies that the stack is to be disabled and ss_sp and ss_size are ignored. If SS_DISABLE is not set, the stack will be enabled. If oss is not NULL, the stack state may be either SS_ONSTACK or SS_DISABLE. The value SS_ONSTACK indicates that the process is currently executing on the alternate stack and that any attempt to modify it during execution will fail. The value SS_DISABLE indicates that the current signal stack is disabled. Specifies the size of the stack.
defines the average number of
bytes used when allocating an alternate stack area. The value
defines the minimum stack size for a signal handler. When processing
an alternate stack size, your program should include these values in the stack
requirement to plan for the overhead of the operating system.
Upon successful completion, zero (0) is returned.
On error, the value
is returned and
is set to indicate the error.
to the specified values for the following conditions:
parameter is not a null pointer,
member pointed to by
contains flags other than SS_DISABLE.
The size of the alternate stack area is less than MINSIGSTKSZ.
An attempt was made to modify an active stack.
Functions: getcontext(2), sigaction(2)