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    <p>Short answer: no, there isn't any way to tell automatically whether the function will behave differently according to whether the declaration of a local variable is static or not. You just have to examine the logic of each function that uses globals in the original code.</p> <p>However, if replacing a global variable with a static local-scope variable means the function is not re-entrant, then it wasn't re-entrant when it was a global, either. So I don't think that changing a global to a static local-scope variable will make your functions any less re-entrant than they were to start with. </p> <p>Provided that the global really was used only in that scope (which the compiler/linker should confirm when you remove the global), the behaviour should be close to the same. There may or may not be issues over when things are initialized, I can't remember what the standard says: if static initialization occurs in C the same time it does in C++, when execution first reaches the declaration, then you might have changed a concurrency-safe function into a non-concurrency-safe one.</p> <p>Working out whether a function is safe for re-entrancy also requires looking at the logic. Unless the standard says otherwise (I haven't checked), a function isn't automatically non-re-entrant just because it declares a static variable. But if it uses either a global or a static in any significant way, you can assume that it's non-re-entrant. If there isn't synchronization then assume it's also non-concurrency-safe.</p> <p>Finally, good luck. Sounds like this code is a long way from where you want it to be...</p>
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    1. PORefactoring global to local. Should they be static or not?
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    1. USSteve Jessop
    1. USSteve Jessop
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    1. COIt is easier to make global variable multitasking aware by protecting it with mutex, from dealing with procedure scope static variable.
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    2. CONothing prevents you from protecting a local static variable with a mutex, the same as you did with the global variable. In fact, if a global variable has a related mutex, you should be moving that mutex in scope as well.
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    3. COMaybe it is implementation related, but the mutexes in the RTOS that I'm working with, are always globals. Therefore, making the protected variable also global is more intuitive for me.
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