39 by handlers for ordinary signals. |
39 by handlers for ordinary signals. |
40 I.e. a signal handler for a normal signal will not handle a query |
40 I.e. a signal handler for a normal signal will not handle a query |
41 signal. Thus, these bypass anySignal handlers. |
41 signal. Thus, these bypass anySignal handlers. |
42 If unhandled, no error is raised, instead they are simply ignored |
42 If unhandled, no error is raised, instead they are simply ignored |
43 (as opposed to normal signals, which raise an unhandled signal exception). |
43 (as opposed to normal signals, which raise an unhandled signal exception). |
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44 QuerySignals are also ignored, if a handler exists, but rejects. |
44 |
45 |
45 Their main use is to implement up-Queries via signals even if intermediate |
46 Their main use is to implement up-Queries via signals, that work even |
46 errorSignal handlers are present (which is not possible with ordinary signals). |
47 if intermediate errorSignal handlers are present |
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48 (which is not possible with ordinary signals, since errorSignal handlers |
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49 would catch those signals). |
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50 |
47 Code deep down in the calling hierarchy can post such an up-Query to ask |
51 Code deep down in the calling hierarchy can post such an up-Query to ask |
48 for some information in return or to pass some information upward. |
52 for some information in return or to pass some information upward. |
49 |
53 |
50 For example, the activityNotification mechanism is built on top of this: |
54 For example, the activityNotification mechanism is built on top of this: |
51 everyone can send such a notification which is either handled by someone |
55 everyone can send such a notification which is either handled by someone |