/[ascend]/trunk/base/generic/utilities/ascSignal.h
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revision 967 by johnpye, Thu Dec 7 14:47:15 2006 UTC revision 968 by johnpye, Mon Dec 18 05:49:00 2006 UTC
# Line 49  Line 49 
49         Asc_SignHandlerPop(SIGFPE,Asc_SignalTrap);         Asc_SignHandlerPop(SIGFPE,Asc_SignalTrap);
50         Asc_SignalDestroy();         Asc_SignalDestroy();
51      </pre>      </pre>
52   *  This example uses the built-in signal handler Asc_SignalTrap()  
53   *  and the global <code>jmp_buf</code> g_fpe_env.  After initializing      This example uses the built-in signal handler Asc_SignalTrap()
54   *  the signal manager and registering the handler, <code>setjmp</code>      and the global <code>jmp_buf</code> g_fpe_env.  After initializing
55   *  is used to select normal and exception paths.  The <code>setjmp</code>      the signal manager and registering the handler, <code>setjmp</code>
56   *  returns 0 when initially called and the sqrt(x) is calculated.  If      is used to select normal and exception paths.  The <code>setjmp</code>
57   *  x is negative, a SIGFPE exception occurs and the handler is called.  It      returns 0 when initially called and the sqrt(x) is calculated.  If
58   *  uses <code>lngjmp</code> and returns to the if statement, and now      x is negative, a SIGFPE exception occurs and the handler is called.  It
59   *  <setjmp> returns non-zero and the <code>else</code> clause is executed.      uses <code>lngjmp</code> and returns to the if statement, and now
60   *  Finally, the handler is removed and the signal manager cleaned up.<br><br>      'setjmp' returns non-zero and the <code>else</code> clause is executed.
61   *      Finally, the handler is removed and the signal manager cleaned up.<br><br>
62   *  The stack mechanism also allows nested handlers to be registered.  It is      
63   *  important to note that nested handlers for the same signal type cannot      The stack mechanism also allows nested handlers to be registered.  It is
64   *  both use Asc_SignalTrap() as the handler.  This is because different      important to note that nested handlers for the same signal type cannot
65   *  <code>jmp_buf</code> variables must be used and Asc_SignalTrap() uses      both use Asc_SignalTrap() as the handler.  This is because different
66   *  the same global <code>jmp_buf</code> each time.  However, you can use      <code>jmp_buf</code> variables must be used and Asc_SignalTrap() uses
67   *  custome <code>jmp_buf</code>'s and handlers:      the same global <code>jmp_buf</code> each time.  However, you can use
68   *  <pre>      custome <code>jmp_buf</code>'s and handlers:
69   *     Asc_SignalInit();  
70   *     Asc_SignalHandlerPush(SIGFPE, Asc_SignalTrap);      <pre>
71   *     if (setjmp(g_fpe_env) == 0) {         Asc_SignalInit();
72   *         y = sqrt(x);         Asc_SignalHandlerPush(SIGFPE, Asc_SignalTrap);
73   *         Asc_SignalHandlerPush(SIGFPE, my_handler);         if (setjmp(g_fpe_env) == 0) {
74   *         if (setjmp(my_jmp_buf) == 0) {             y = sqrt(x);
75   *             y = z/x;             Asc_SignalHandlerPush(SIGFPE, my_handler);
76   *         } else {             if (setjmp(my_jmp_buf) == 0) {
77   *             Asc_Panic(1, NULL, "Div by zero error.");                 y = z/x;
78   *         }             } else {
79   *         Asc_SignHandlerPop(SIGFPE, my_handler);                 Asc_Panic(1, NULL, "Div by zero error.");
80   *     } else {             }
81   *       y = sqrt(-x);             Asc_SignHandlerPop(SIGFPE, my_handler);
82   *     }         } else {
83   *     Asc_SignHandlerPop(SIGFPE,Asc_SignalTrap);           y = sqrt(-x);
84   *     Asc_SignalDestroy();         }
85   *  </pre>         Asc_SignHandlerPop(SIGFPE,Asc_SignalTrap);
86   *  Here, exceptions in the sqrt(x) calculation are handled by the standard         Asc_SignalDestroy();
87   *  Asc_SignalTrap(), while the division is handled by my_handler.<br><br>      </pre>
88   *      
89   *  Avoid mixing use of the signal manager with direct calls to signal().      Here, exceptions in the sqrt(x) calculation are handled by the standard
90   *  Once Asc_SignalInit() has been called, use of signal() directly is likely      Asc_SignalTrap(), while the division is handled by my_handler.<br><br>
91   *  to be lost or to corrupt the managed handlers.<br><br>      
92   *      Avoid mixing use of the signal manager with direct calls to signal().
93   *  Another warning: setjmp is expensive if called inside a fast loop.      Once Asc_SignalInit() has been called, use of signal() directly is likely
94        to be lost or to corrupt the managed handlers.<br><br>
95        
96        Another warning: setjmp is expensive if called inside a fast loop.
97    
98      Requires:      Requires:
99      #include "utilities/ascConfig.h"      #include "utilities/ascConfig.h"
# Line 112  Line 115 
115  #  include <unistd.h>  #  include <unistd.h>
116  #endif  #endif
117    
118    #ifdef __WIN32__
119    # define FPRESET _fpreset()
120    #else
121    # define FPRESET (void)0
122    #endif
123    
124  typedef void SigHandlerFn(int);  typedef void SigHandlerFn(int);
125  /**< Signature of a signal handling function. */  /**< Signature of a signal handling function. */
126    
# Line 220  ASC_DLLSPEC(void ) Asc_SignalRecover(int Line 229  ASC_DLLSPEC(void ) Asc_SignalRecover(int
229   *               compiler/platform.   *               compiler/platform.
230   */   */
231    
232    ASC_DLLSPEC(int ) Asc_SignalHandlerPushDefault(int signum);
233  ASC_DLLSPEC(int ) Asc_SignalHandlerPush(int signum, SigHandlerFn *func);  ASC_DLLSPEC(int ) Asc_SignalHandlerPush(int signum, SigHandlerFn *func);
234  /**<  /**<
235   * Adds a handler to the stack of signal handlers for the given signal.   * Adds a handler to the stack of signal handlers for the given signal.
# Line 242  ASC_DLLSPEC(int ) Asc_SignalHandlerPush( Line 252  ASC_DLLSPEC(int ) Asc_SignalHandlerPush(
252   *        popping an unintended handler.   *        popping an unintended handler.
253   */   */
254    
255    ASC_DLLSPEC(int ) Asc_SignalHandlerPopDefault(int signum);
256  ASC_DLLSPEC(int ) Asc_SignalHandlerPop(int signum, SigHandlerFn *func);  ASC_DLLSPEC(int ) Asc_SignalHandlerPop(int signum, SigHandlerFn *func);
257  /**<  /**<
258   *  Removes the last-pushed handler from the stack for signum signal types.   *  Removes the last-pushed handler from the stack for signum signal types.
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john.pye@anu.edu.au
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