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Mac Forum / Programming / CodeWarrior / March 2004static globals and vector<bool>
In PPx (CW 9.1), I have a class, to manage multiprocessing, instantiated once as a static global object, theCMP. This class has a static member static vector<bool> Waiting; The class ctor is automatically called prior to main() and, at that time, Waiting is resized to the number of active processors. Debugging confirms this. However, the first time theCMP is subsequently used the size of Waiting has decreased to zero, having been cleared (somehow automatically). Debugging shows the deleter being called deep within library code. [I do not call it.] Note, all of the static members of this class that are scalars retain their correct values -- e.g., numProcessors. It is just this vector that is cleared. Is this the way the STL is supposed to behave or is this some kind of bug? TIA. -- Mike McLaughlin > This class has a static member > [quoted text clipped - 8 lines] > Debugging shows the deleter being called deep within library code. [I > do not call it.] Having a static member of a unique global object is overegging it. Since you only have one object, Waiting can be a normal member variable of it. A static member will be initialised independently of the object, and the implementation is free to do these two initialisations in either order unless both variables (i.e. Waiting and theCMP) are defined in the same translation unit. In fact, unless the definitions are in the same TU with theCMP after Waiting, your use of the static member in the class constructor is undefined behaviour. Your observations are consistent with the static member initialisation being after that of the global object. (Also note that std::vector<bool> is 'wierd'; unless you really, really need to save every last byte, you might be better off with deque<bool>.) Best wishes, Matthew Collett  SignatureThose who assert that the mathematical sciences have nothing to say about the good or the beautiful are mistaken. -- Aristotle I tried making Waiting[] non-static but then I get an error: "Illegal use of non-static member" as soon as I try to modify it. That is, the code will not compile. Note: Much of the MP manager seems to require static members for various things which is why I made everything static in the first place. All was working until I added this vector<bool>. >>This class has a static member >> [quoted text clipped - 25 lines] > Best wishes, > Matthew Collett > >>static vector<bool> Waiting; > > [quoted text clipped - 11 lines] > things which is why I made everything static in the first place. All > was working until I added this vector<bool>. That's odd: static or not is a C++ distinction, not one that should make any difference to the OSes MP manager. It's difficult to say more without seeing the (minimal) code that produces the error. Best wishes, Matthew Collett SignatureThose who assert that the mathematical sciences have nothing to say about the good or the beautiful are mistaken. -- Aristotle > "Illegal use of non-static member" That would be because you're still trying to access it as though it were static, rather than treating it as a "normal" class member. |
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