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Annotation of coherent/a/usr/man/ALL/setjmp, revision 1.1

1.1     ! root        1: 
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        !             3: setjmp()                 General Function                setjmp()
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        !             8: Perform non-local goto
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        !            10: #include <setjmp.h>
        !            11: iinntt sseettjjmmpp(_e_n_v) jjmmpp_bbuuff _e_n_v;
        !            12: 
        !            13: The function call is the only mechanism that C provides to trans-
        !            14: fer control  between functions.  This mechanism,  however, is in-
        !            15: adequate for some purposes, such as handling unexpected errors or
        !            16: interrupts at  lower levels of  a program.  To  answer this need,
        !            17: sseettjjmmpp helps to  provide a non-local _g_o_t_o facility.  sseettjjmmpp saves
        !            18: a stack  context in _e_n_v, and returns value  zero.  The stack con-
        !            19: text can be restored  with the function longjmp.  The type decla-
        !            20: ration for  jjmmpp_bbuuff is in the header  file sseettjjmmpp.hh.  The context
        !            21: saved  includes the  program  counter, stack  pointer, and  stack
        !            22: frame.
        !            23: 
        !            24: ***** Example *****
        !            25: 
        !            26: The following gives a simple example of setjmp and longjmp.
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        !            29: #include <setjmp.h>
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        !            33: jmp_buf env;    /* place for setjmp to store its environment */
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        !            37: main()
        !            38: {
        !            39:         int rc;
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        !            43:         if(rc = setjmp(env)) { /* we come here on return */
        !            44:                 printf("First char was %c\n", rc);
        !            45:                 exit(0);
        !            46:         }
        !            47:         subfun();       /* this never returns */
        !            48: }
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        !            50: 
        !            51: 
        !            52: subfun()
        !            53: {
        !            54:         char buf[80];
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        !            63: 
        !            64: COHERENT Lexicon                                           Page 1
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        !            69: setjmp()                 General Function                setjmp()
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        !            73:         do {
        !            74:                 printf("Enter some data\n");
        !            75:                 gets(buf);      /* get data */
        !            76:         } while(!buf[0]);       /* retry on null line */
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        !            80:         longjmp(env, buf[0]);   /* buf[0] must be non zero */
        !            81: }
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        !            83: 
        !            84: ***** See Also *****
        !            85: 
        !            86: general functions, getenv(), longjmp()
        !            87: 
        !            88: ***** Notes *****
        !            89: 
        !            90: Programmers should  note that many user-level  routines cannot be
        !            91: interrupted and reentered  safely.  For that reason, improper use
        !            92: of setjmp  and longjmp  can create mysterious  and irreproducible
        !            93: bugs.  The  use of longjmp to exit  interrupt exception or signal
        !            94: handlers is particularly hazardous.
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        !           130: COHERENT Lexicon                                           Page 2
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