thr_stksegment(3c) [sunos man page]

thr_stksegment(3C)					   Standard C Library Functions 					thr_stksegment(3C)

NAME

       thr_stksegment - get thread stack address and size

SYNOPSIS

       cc -mt [ flag... ] file...[ library... ]
       #include <thread.h>
       #include <signal.h>

       int thr_stksegment(stack_t *ss);

DESCRIPTION

       The thr_stksegment() function returns, in its stack_t argument, the address and size of the calling thread's stack.

       The stack_t structure includes the following members:

       void   *ss_sp
       size_t ss_size
       int    ss_flags

       On  successful  return  from  thr_stksegment(),	ss_sp contains the high address of the caller's stack and ss_size contains the size of the
       stack in bytes.	The ss_flags member is always 0. Note that the meaning of ss_sp is reversed from other uses of	stack_t  such  as  sigalt-
       stack(2) where ss_sp is the low address.

       The  stack  information	provided  by  thr_stksegment()	is typically used by debuggers, garbage collectors, and similar applications. Most
       applications should not require such information.

RETURN VALUES

       The  thr_stksegment() function returns  0 if the thread stack address and size were successfully retrieved.  Otherwise, it returns  a  non-
       zero error value.

ERRORS

       The  thr_stksegment() function will fail if:

       EAGAIN	       The  stack  information	for  the  thread  is not available because the thread's initialization is not yet complete, or the
		       thread is an internal thread.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sigaltstack(2), thr_create(3C), attributes(5)

SunOS 5.10							    15 Jun 2000 						thr_stksegment(3C)

SIGALTSTACK(2)						      BSD System Calls Manual						    SIGALTSTACK(2)

NAME

     sigaltstack -- set and/or get signal stack context

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <signal.h>

     typedef struct {
	     char    *ss_sp;
	     size_t  ss_size;
	     int     ss_flags;
     } stack_t;

     int
     sigaltstack(const stack_t * restrict ss, stack_t * restrict oss);

DESCRIPTION

     The sigaltstack() system call allows defining an alternate stack on which signals are to be processed for the current thread.  If ss is non-
     zero, it specifies a pointer to and the size of a signal stack on which to deliver signals.  When a signal's action indicates its handler
     should execute on the signal stack (specified with a sigaction(2) system call), the system checks to see if the thread is currently executing
     on that stack.  If the thread is not currently executing on the signal stack, the system arranges a switch to the signal stack for the dura-
     tion of the signal handler's execution.

     An active stack cannot be modified.

     If SS_DISABLE is set in ss_flags, ss_sp and ss_size are ignored and the signal stack will be disabled.  A disabled stack will cause all sig-
     nals to be taken on the regular user stack.  If the stack is later re-enabled then all signals that were specified to be processed on an
     alternate stack will resume doing so.

     If oss is non-zero, the current signal stack state is returned.  The ss_flags field will contain the value SS_ONSTACK if the thread is cur-
     rently on a signal stack and SS_DISABLE if the signal stack is currently disabled.

NOTES

     The value SIGSTKSZ is defined to be the number of bytes/chars that would be used to cover the usual case when allocating an alternate stack
     area.  The following code fragment is typically used to allocate an alternate stack.

	   if ((sigstk.ss_sp = malloc(SIGSTKSZ)) == NULL)
		   /* error return */
	   sigstk.ss_size = SIGSTKSZ;
	   sigstk.ss_flags = 0;
	   if (sigaltstack(&sigstk, NULL) < 0)
		   perror("sigaltstack");
     An alternative approach is provided for programs with signal handlers that require a specific amount of stack space other than the default
     size.  The value MINSIGSTKSZ is defined to be the number of bytes/chars that is required by the operating system to implement the alternate
     stack feature.  In computing an alternate stack size, programs should add MINSIGSTKSZ to their stack requirements to allow for the operating
     system overhead.

     Signal stacks are automatically adjusted for the direction of stack growth and alignment requirements.  Signal stacks may or may not be pro-
     tected by the hardware and are not ``grown'' automatically as is done for the normal stack.  If the stack overflows and this space is not
     protected unpredictable results may occur.

RETURN VALUES

     The sigaltstack() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to
     indicate the error.

ERRORS

     The sigaltstack() system call will fail and the signal stack context will remain unchanged if one of the following occurs.

     [EFAULT]		Either ss or oss points to memory that is not a valid part of the process address space.

     [EPERM]		An attempt was made to modify an active stack.

     [EINVAL]		The ss_flags field was invalid.

     [ENOMEM]		Size of alternate stack area is less than or equal to MINSIGSTKSZ.

SEE ALSO

     sigaction(2), setjmp(3)

HISTORY

     The predecessor to sigaltstack(), the sigstack() system call, appeared in 4.2BSD.

BSD
								    May 6, 2010 							       BSD