01-22-2003
That would just be more of the same. Anything with the potential to result in an unlimited depth of function calls will eventually exhaust resources or consume far too many resources.
Ideally the each function should simply return when they are done. And the main function should simply have a loop that displays the menu and calls the proper function. This is the structured way and it's the only way I program.
But lots of people disagree with me (including such people as Richard Stevens and Dennis Ritchie). So I should tell you that there is also setjmp()/longjmp(). You call setjmp at some point in your program...like just before you print the main menu. Later, even in some other function, you call longjmp. And then the next thing that happens is that you're back right after the setjmp and stack pointer is magically unwound as well. This will not leak memory.
A third technique is to re-exec the program. I think that this is pathetic and here I can claim broad support.
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LEARN ABOUT ULTRIX
longjmp
setjmp(3) Library Functions Manual setjmp(3)
Name
setjmp, longjmp - non-local goto
Syntax
#include <setjmp.h>
int setjmp (env)
jmp_buf env;
void longjmp (env, val)
jmp_buf env;
int val;
Description
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
Examples
#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);
exit(0);
}
(void) printf("value of i on 1st return from setjmp: %d0, i);
i = 1;
g();
/*NOTREACHED*/
}
g()
{
longjmp(env, 1);
/*NOTREACHED*/
}
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.
Restrictions
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
signal(2).
RISC setjmp(3)