reentrancy

问题 In C I know about the recursive function but I heard about the re-entrant function. What is that? And whats the difference between them? 回答1: A function is re-entrant if it supports having multiple threads of execution "going through" it at the same time. This might be due to actual multi-threading, and I use this case below, or due to other things as pointed out by other posters. Multi-threading was the first that came to mind, and is perhaps also the easiest to understand, so I focused on

问题 Reentrancy means that locks are acquired on a per-thread rather than per-invocation basis. Since an intrinsic lock is held by a thread, doesn't it mean that a thread run once equals an invocation basis? Thank you, it seems mean that: in a thread,if I get a lock lockA when process function doA which call function doB , and doB also need a lock lockA ,then there wil be a reentrancy. In Java, this phenomenon is acquired per thread, so I needn't consider deadlocks? 回答1: Reentrancy means that

问题 In UNIX systems we know malloc() is a non-reentrant function (system call). Why is that? Similarly, printf() also is said to be non-reentrant; why? I know the definition of re-entrancy, but I wanted to know why it applies to these functions. What prevents them being guaranteed reentrant? 回答1: malloc and printf usually use global structures, and employ lock-based synchronization internally. That's why they're not reentrant. The malloc function could either be thread-safe or thread-unsafe. Both

问题 Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely

问题 Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely

问题 Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely

问题 void reverse_string(char* string, int str_size) { char tmp; int i = 0; int j = str_size - 1; while (i < j) { tmp = string[i]; string[i] = string[j]; string[j] = tmp; ++i; --j; } } I think this function is reentrant, since it doesn't use any global variable. It only modifies the arguments. My question is: is this function reentrant? if it is, is my argument good enough? thanks in advance 回答1: Yes, this is a reentrant function. Reentrant functions are defined as those that can be called whilst

问题 As Peter Duniho points out in a comment here, I was fixated on a red herring when I should have been focusing on something else altogether. When I use Symbol.Barcode.Reader and Symbol.Barcode.ReaderData in one form, they work fine. I use them as I document here. However, when I go from one form that uses the barcode scanning code to another one that also does, all Dallas breaks loose. I get the following exception in the second form, on startup: Symbol.Exceptions.OperationFailureException:

问题 I have a program that needs to load a lot of QPixmaps. I split the loading of the pixmaps in several jobs using QtConcurrent::mappedReduced (I actually load a bunch of QGraphicPixmapItem s). The loading function calls only the constructors of the QPixmap s/ QGraphicItem s, it does not attempt to perform any drawing, and it does not communicate with the rest of the world (at least through my code) until the loading is finished. I get some random crashes during the initialization (say 1% of the

问题 I have got a VI which execution type is set to be as preallocated clone reentrant. In the VI i have several SubVIs. Should I set the execution type of SubVIs the same as in the main VI? Thank you 回答1: Setting a VI to be reentrant doesn't automatically make its subVIs reentrant - if it did, this would break some of the use cases for non-reentrant VIs, such as serialising access to single resources or maintaining stored state data between calls. So to decide whether a subVI needs to be