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Annotation of coherent/a/usr/man/ALL/setjmp, revision 1.1.1.1

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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;
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                     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.
                     27: 
                     28: 
                     29: #include <setjmp.h>
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                     31: 
                     32: 
                     33: jmp_buf env;    /* place for setjmp to store its environment */
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                     36: 
                     37: main()
                     38: {
                     39:         int rc;
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                     42: 
                     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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                     64: COHERENT Lexicon                                           Page 1
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                     68: 
                     69: setjmp()                 General Function                setjmp()
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                     72: 
                     73:         do {
                     74:                 printf("Enter some data\n");
                     75:                 gets(buf);      /* get data */
                     76:         } while(!buf[0]);       /* retry on null line */
                     77: 
                     78: 
                     79: 
                     80:         longjmp(env, buf[0]);   /* buf[0] must be non zero */
                     81: }
                     82: 
                     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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