proc/bad_longjmp.c

This is proc/bad_longjmp.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is the solution to Exercise 6-2 (page 138).

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

Download proc/bad_longjmp.c

Cover of The Linux Programming Interface

Distribution version

Function list (Bold in this list means a function is not static)

doJump()
setJump2()
setJump()
main()

/* bad_longjmp.c

   Demonstrate the incorrect use of longjmp() to jump into a function
   that has already returned. As a consequence the program is killed by
   a SIGSEGV signal (Segmentation fault).
*/
#include <setjmp.h>
#include "tlpi_hdr.h"

static jmp_buf env;     /* Global buffer for saving environment */

static void
doJump(void)
{
    printf("Entered doJump\n");
    longjmp(env, 2);
    printf("Exiting doJump\n");
}

static void
setJump2(void)
{
    printf("Entered setJump2\n");
    setjmp(env);
    printf("Exiting setJump2\n");
}

static void
setJump(void)
{
    printf("Entered setJump\n");
    setJump2();
    printf("Exiting setJump\n");
}

int
main(int argc, char *argv[])
{
    setJump();
    doJump();
    printf("Back at main\n");

    exit(EXIT_SUCCESS);
}

Download proc/bad_longjmp.c

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