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setjmp(3) [ultrix man page]

setjmp(3)						     Library Functions Manual							 setjmp(3)

       setjmp, longjmp - non-local goto

       #include <setjmp.h>

       int setjmp (env)
       jmp_buf env;

       void longjmp (env, val)
       jmp_buf env;
       int val;

       The and functions help deal with errors and interrupts encountered in a low-level subroutine of a program.

       The function saves its stack environment in env (whose type, jmp_buf, is defined in the <setjmp.h> header file) for later use by It returns
       the value 0.

       The function restores the environment saved by the last call of with the corresponding env argument.   After  finishes,	program  execution
       continues  as if the corresponding call of (which must not itself have returned in the interim) had just returned the value val.  The func-
       tion cannot cause to return the value 0.  If is invoked with a second argument of 0, returns 1.	At the time of the second return from  all
       accessible  data  have  values as of the time is called.  However, global variables have the expected values.  For example, those as of the
       time of the

       #include <setjmp.h>

       jmp_buf env;
       int i = 0;
       main ()
	    void exit();

	    if(setjmp(env) != 0) {
		 (void) printf("value of i on 2nd return from setjmp: %d0, i);
	    (void) printf("value of i on 1st return from setjmp: %d0, i);
	    i = 1;

	    longjmp(env, 1);

       If the a.out resulting from this C language code is run, the output is as follows:
       value of i on 1st return from setjmp:0

       value of i on 2nd return from setjmp:1
       Unexpected behavior occurs if is called without a previous call to or when the last such call was in a function which has since returned.

       The values of the registers on the second return from are register values at the time of the first call to not those of the Thus, variables
       in a given function can produce unexpected results in the presence of depending on whether they are register or stack variables.

See Also

								       RISC								 setjmp(3)

Check Out this Related Man Page

LONGJMP(3)							 Library functions							LONGJMP(3)

longjmp, siglongjmp - non-local jump to a saved stack context SYNOPSIS
#include <setjmp.h> void longjmp(jmp_buf env, int val); void siglongjmp(sigjmp_buf env, int val); DESCRIPTION
longjmp() and setjmp() are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. longjmp() restores the environment saved by the last call of setjmp() with the corresponding env argument. After longjmp() is completed, program execution continues as if the corresponding call of setjmp() had just returned the value val. longjmp() cannot cause 0 to be returned. If longjmp is invoked with a second argument of 0, 1 will be returned instead. siglongjmp() is similar to longjmp() except for the type of its env argument. If the sigsetjmp() call that set this env used a nonzero savesigs flag, siglongjmp() also restores the set of blocked signals. RETURN VALUE
These functions never return. CONFORMING TO
POSIX does not specify whether longjmp will restore the signal context. If you want to save and restore signal masks, use siglongjmp. longjmp() and siglongjmp() make programs hard to understand and maintain. If possible an alternative should be used. SEE ALSO
setjmp(3), sigsetjmp(3) 1997-03-02 LONGJMP(3)
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