But thisis sloppy because there's this high level variable (possible several of them or maybe a struct or nested class) which is only there to serve one method. Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_u64 on Intel CPUs. Is it appropriate to ignore emails from a student asking obvious questions? Anyway, I rather dislike when people say "why wouldwant to do that?" Plenty of other OO languages support it and the world hasn't ended because of it. Static locals would obviously be useful to at least some people. Later replies misunderstood the original issue, including the one that you noted, which also entirelymissed the point of the original question. I just edited the question. variables with limited visibility.) and a new one should be started that perhapscontains a link to the old one to provide context for the discussion. Just because you don't see the benefit of a particular feature, or you view it as "bad" doesn't In C++, it avoids the construction/destruction between calls, but could there be any other benefit? There does not have to be any code running all the time.Therefore a static variable has the scope of a local variable but the lifetime of a module level variable.Makes a variable persistent even after the procedure has completed.The next execution of the routine can access the previous value.It is the lifetime of a variable that determines its existence, the scope determines its visibility. The memory model would need a major redesign to allow for their creation and storoage. Here, 'a' is a local variable for function fun, it is created and destroyed whenever the function is called. I understand exactly what you are talking about and it has nothing Well I do. Just check for nullptr, and only create instance on heap first time. In both cases, construction will happen when GetInstance is first called. A local static variable is a variable that can maintain its value from one function call to another and it will exist until the program ends. I don't see how this is any different from a class-level We can't let lack of imagination or thinking too far inside of the box limit development. If you are concerned about inherited types modifying a private static variable declared at the class level, then declarethe class assealed. And then you browse the members of your class, and the list is clogged by half of them that are state private fields used by one method alone each, that should be static local variables, not appearing in the list of class members. Use an instance variable---no static declaration---to per instance actually serve? class, even private, is what could be seen and modified while the method is not yet done, and would pose the very problem you mention. C++ Primer says. the state variables in the method(s) calling this method, passing the data in each time as a reference. Connecting three parallel LED strips to the same power supply. value Any value to initialize the variable. Beides, a private static member cannot be accessed by derived classes anyway. Use an instance variable---no static declaration---to "static variables inside functions (local variables that retain their value between calls)". The static variables are alive till the execution of the program. There are many applications for this but without the functionality we tend to code around it. So, given that the CLR can support Difference between static class and singleton pattern? ", well, here are reasons why we'd want to do that. However, the static keyword confines it to the scope of its function, like a local variable. C++ guarantees that static local objects will be destroyed in reverse order to their construction. I just want others to see both sides too. ? How could my characters be tricked into thinking they are on Mars? I would call it object oriented, instead of procedure driven. A. The only code we can't just create features without any practical applications either, so I see both sides of this. Asking for help, clarification, or responding to other answers. There are thread/race issues if 2 threads try to access the static instance overlapping, if the access is the first access (when constructor is run). A. Arguing about what other languages do and how it would great to have that feature is an argument that Prefixtablenameswithdefaultschemaname if set, //staticregexdefinedabove. Moreover, it is generally best to put all the global declarations near the starting of the program, before the 1 st function. ). None. is waste of time. If it does what you want in the way you want it, then it's all good. And if that restriction exists just because people keep asking "why would rev2022.12.11.43106. Eclectic? The only possibly arguable downside, is the confusion between the two different meanings the keyword "static" would have, when used in declaring local variables, and elsewhere. In this scenario the "static" keyword has different meanings (just like for example "using" currently with access is the code that you are writing for your own class. it and the world hasn't ended because of it. Local, Global , Static Variables (in C) - Types of variables. any differences generally? Aside fromthe fact that it goes completely against the grain ofhow the CLR currentlyworks, what purpose would that featureserve? Finally, VB allows them, and its C/C++ common practice. static var - when the class object disposes, But that clutters the method signature with "unnecessary" housekeeping, and it needs to be duplicated if calling from somewhere else. 'v' is a global variable which is remaining there throughout the program inside the code section and both functions can access it. has in C#): http://msdn.microsoft.com/en-us/library/s1sb61xd.aspx. Is it appropriate to ignore emails from a student asking obvious questions? The original question asked for a Thank-you. I don't see the problem or the need. When a local static variable is created, it should be assigned an initial value. trying to debug the code when it does not work. Static in C. Static is a keyword used in C programming language. Then again, Can we keep alcoholic beverages indefinitely? If they are local variables, then their value persists when execution leaves their scope. I suppose it could skip the check for a static http://rudedog2.spaces.live.com/default.aspx, Javier AP already pointed out that there is no difference in implementation, "And once compiled they can be implemented as the same thing. ", well, here are reasons why we'd want to do that. When b is removed from static storage, that memory will remain until the heap is finally torn down. Why are elementwise additions much faster in separate loops than in a combined loop? In C++, a character in single quotes is a character literal. This is why old threadsare bestleft alone, However, the value of the static variable persists between two function calls. A local static variable is a variable, whose lifetime doesn't stop with a function call where it is declared. I suppose it could skip the check for a static All function calls share the same copy of local static variables. The location will be different. A field of the That individual made a snide remark of their own. Every single language feature can be claimed to be used both properly and improperly, neither of which If you lack the discipline to reference a static variable in your code from only a single location or method, then I do not know what to say. I stumbled across this thread because I was specifically looking for a way to make a variable in method static. I ask again, what purpose would having a static variable per instance serve? Incidentally, global variables can be declared in IL. For example, consider the below function. that is when the method-level static vars can get GC'd. The following are the primary uses of a static keyword: i. EDIT: Here is an SO question where the answer contains relevant ref to standard: Heap/dynamic vs. static memory allocation for C++ singleton class instance. That just leaves your question about memory location. (to be clear, I'm speaking here about const vs. non-const, not static vs. the state variables in the method(s) calling this method, passing the data in each time as a reference. For example how many times the method was called on any of the class objects. In 'C', static local variables are global variables with a limited scope. The problem will turn into a murder mystery, a "whodunit." Most variables stored in the array (i.e., in main memory) are larger than one byte, so the address of each variable is the index of the first byte of that variable. How does legislative oversight work in Switzerland when there is technically no "opposition" in parliament? Code is code, there is no proper or improper. I ask again, what purpose would having a static variable per instance serve? Here is a concrete example where a static local variable would be useful: Here the tableName regular expression should be static, because it doesn't change and compiling a regex is fairly expensive. There should be no reason for their lack of existance. Find centralized, trusted content and collaborate around the technologies you use most. The same can also be achieved by using global variables or static member variables. There are many applications for this but without the functionality we tend to code around it. You would normally use a static variable in cases where you wish to preserve the value of a variable inside a function. "static variables inside functions (local variables that retain their value between calls)". Why is Singapore currently considered to be a dictatorial regime and a multi-party democracy by different publications. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. Sure, none of this is insurmountable, but we tend to go through these minor contortionsas a matter of coursebecause of a language restriction that we all tend to accept. They could be allowed in any .NET language, which must compile to IL, and it would need no re-design whatsoever of the CLR. For the compilers it's a very small change. What purposewould a local static variable serve? It woulddiscarded when the method completes. If you wish for other code to be able modify it while your method executes, be my guest When to implement a static local variable as a hidden instance field or a hidden static field? A. I see no compelling reason why C# should include this feature. It goes totally against the grain of theway in which managed memory works. The relevant section is 6.7.4, see e.g. Question 1: Describe, how can we make a local variable global in the C++ language?. Making statements based on opinion; back them up with references or personal experience. I could also keep One of us is misunderstanding the other. If it does what you want in the way you want it, then it's all good. It ought to be a staticlocalvariable. @MarkRansom: a) that would depend on the size of the stack, b) how many different things like this I've got. Say you have a doSomething() method in your class, and you use a field, say int doSomethingCount to count how many times this one method was called. It ought to be a staticlocalvariable. But, that is not exactly what theOP asked about. Thisthread was a question, not a discussion. Butnow you have gone off into something elsethat is completely different, nowwe havestatic methods with local static variables. I could say you lack the discipline to control your But see, in the first place you name this field in a self documenting way, to let it be known that it's to be used by that method alone. At that stage it would be considered "leaked", and the destructor (if any) for B will never be invoked. A static variable is a local variable whose life time is the lifetime of the entire module, not just the procedure. In my specific case right now I have a method that gets called numerous times. A C style static local variable would not be visible outside the method, and so couldn't be modified, even by members of the same class; but its lifetime would be the same as the instance (if declared in an instance member) or the class (if declared in a that already happens with "using" for example; and it's also the case in other languages. Mark the best replies as answers. Arguing about what other languages do and how it would great to have that feature is an argument that They could be allowed in any .NET language, which must compile to IL, and it would need no re-design whatsoever of the CLR. CGAC2022 Day 10: Help Santa sort presents! You are asking for global variables. Internal Static Variables: Internal Static variables are defined as those having static variables which are declared inside a function and extends up to the end of the particular function. I do not see howthis offers any advantages over what is currently available. "I already said this over a year ago, but regarding implementation/storage: a static local variable in an instance method would simply be an instance field, only invisible outside the method; and a static local variable in a static method would simply OK, so the next solution is, if you want to maintain state then this shouldn't be a method, it should be a class, perhaps with just a single method, perhaps even static. MOSFET is getting very hot at high frequency PWM. A global static variable is one that can only be accessed in the file where it is . Do non-Segwit nodes reject Segwit transactions with invalid signature? Thus the compiler must emit code to guess . . Why would Henry want to close the breach? Just as a class should The scope isn't as constrained as it was in 'C' but that shouldn't be a real problem. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. Just as a class should per instance be stored? If it's, say, a machine generated table of constants for a Times Roman font that I want to have hard-coded in my word-processor, then that wouldn't be a good thing to put on the stack, even if the stack is quite large. Books that explain fundamental chess concepts. But, that is not exactly what theOP asked about. In this scenario the "static" keyword has different meanings (just like for example "using" currently It seems to me that C# has an eclectic design philosophy: if a feature is useful and can be expressed succinctly, it tends to get into the language, even if there may already be a (less convenient) way to do the same thing. Is it possible to hide or delete the new Toolbar in 13.1? You cannot start moving type objects around in memory to allow them todynamically allocate and deallocate static variables per instance. an static field, invisible outside the method. But it should also be local to the function that uses it. we can't just create features without any practical applications either, so I see both sides of this. static member). We can't let lack of imagination or thinking too far inside of the box limit development. #include <iostream> using namespace std; void increase() { static int num = 0; cout << ++num << endl; } int main() { increase(); increase(); return 0; } Output: 1. The scope of a static variable is local to the block in which the variable is defined. Nowadays, C++ has compiler/standards support that automatically makes this static singleton initialization thread-safe. Static variables are stored in initialised data segments. Static locals would obviously be useful to at least some people. Difference between static and shared libraries? So I ask again, what purpose wouldhaving static variables per instanceserve? Observe the output in this case. Notice that inside function func_2() there is a local variable with the same name as a global variable. As mentioned in the question, in C++11 both: (1) and (2) you mentioned are guaranteed by the compiler. "Declaring a static variable outside of the scope that tracks how many time a method is called will result in totaling up the method calls for all of the objects of that type, not just the single instance. track calls on just a single instance.". Also, in C++ the auto keyword no longer means automatic storage duration; it now means . The vars of the method are out of scope and elegible for GC, but here's this static method with local vars that are still referenced. This is an old thread, which has been resurrected completely out of its' original context. But (besides the doubtfully preferable possibility of using another keyword): It's only the compiler that would have to be aware that static local variables have the same scope as fields, but visibility limited to one method. static variable per instance. For the compilers it's a very small change. Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. Local Variable in C: The local variable is a variable that is declared within a function, block (within curly braces), or function argument. For help clarifying this question so that it can be reopened, Not the answer you're looking for? Actually even from the point of view of OOP, or rather data hiding, which is supposedly something aimed at by OOP, allowing this would mean stronger data hiding than disallowing it. How to make voltage plus/minus signs bolder? So there shouldn't be a "major redesign", they are just private members(for instance counts) or static private members (for class counts) that are invisible outside the scope of the method. He didn't ask how YOU write code, he asked how to do static locals static var - when the class object disposes, an static field, invisible outside the method. So there shouldn't be a "major redesign", they are just private members(for instance counts) or static private members (for class counts) that are invisible outside the scope of the method. If static local variables were allowed, they would be better for this purpose, because they would be hidden to the rest of the class, as they should. The rubber protection cover does not pass through the hole in the rim. "Declaring a static variable outside of the scope that tracks how many time a method is called will result in totaling up the method calls for all of the objects of that type, not just the single instance. It extends until the lifetime of a complete program. Help us identify new roles for community members, Proposing a Community-Specific Closure Reason for non-English content. Static variables have a lifetime that lasts until the end of the program. What it does each time is dependent on what it did the last time, so I'd likea couple Booleans andInt32 indexes topreserve state between invocations. What are Static Variables in C++? Global variable in a module or static global variable: Declared at the top of a program. The static variables stay alive till the program gets executed in the end. The syntax of the static variables in C is: static datatype variable_name = value; In this case, value It refers to the value that we use to initialize the variable. Why is the eastern United States green if the wind moves from west to east? This is an old thread, which has been resurrected completely out of its' original context. "Fooling computers since 1971.". has in C#): http://msdn.microsoft.com/en-us/library/s1sb61xd.aspx. Are defenders behind an arrow slit attackable? How does that help anything? Static variables are generally stored in the program's data segment, whereas anything allocated with new will be stored in the heap. In C and C++, what is the advantage of making a local const variable static? That couldrequire a new .cs code module, a duplicate set of'using' statements, static member). How can I fix it? That is not what the thread is about. In my specific case right now I have a method that gets called numerous times. mean that everyone else does. It woulddiscarded when the method completes. If you are concerned about inherited types modifying a private static variable declared at the class level, then declarethe class assealed. Consider the below program, void test(int x, int y) { int a; } In the above program, a, x and y are local variables. per instance actually serve? The vars of the method are out of scope and elegible for GC, but here's this static method with local vars that are still referenced. Are the S&P 500 and Dow Jones Industrial Average securities? You can obtain the same effect using a private module level variable instead of a static variable.It is considered better programming practice to use static variables as this uses a more restictive scope.This helps to prevent accidental changes being made to the variable in other portions of the code. The question does not mention any guarantees from the standard. Well I do. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. In prior lessons, we covered that global variables have static duration, which means they are created when the program starts and destroyed when the program ends. What we're talking about is the exact same thing that other languages like C++ and D have. How would the CLR access them compared to instance variables. Assuming the var is actually const. be an static field, invisible outside the method.". Assuming the initialization does not use other variables, is there any difference between preserving the value between calls, and setting the same constant value each call? Difference between static class and singleton pattern? For example how many times the method was called on any of the class objects. This is not the only post the OP made at the time. There's a major problem with local static variableswithin a method. You could always use one of the hallmarks of OOP and encapsulate such a method within its' own class. Because My opinion is that both private fields and static local variables can be useful. Later replies misunderstood the original issue, including the one that you noted, which also entirelymissed the point of the original question. (Just like in C static local variables are global One of us is misunderstanding the other. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, As an afterthought, there may also be differences in program behaviour when, As mentioned in the question, in C++11 both: (1) and (2) you mentioned are guaranteed by the compiler. To learn more, see our tips on writing great answers. It seems to me that C# has an eclectic design philosophy: if a feature is useful and can be expressed succinctly, it tends to get into the language, even if there may already be a (less convenient) way to do the same thing. It contains local and static variable. Actually even from the point of view of OOP, or rather data hiding, which is supposedly something aimed at by OOP, allowing this would mean stronger data hiding than disallowing it. CGAC2022 Day 10: Help Santa sort presents! And whatever I do, the initializer list will be part of my code, either way. Use an instance variable---no static declaration---to track calls on just a single instance. Where a and b are used only with the main () function because they are local variables declared only . ii. I don't see how that's anything like a global variable. is waste of time. Aside fromthe fact that it goes completely against the grain ofhow the CLR currentlyworks, what purpose would that featureserve? What we're talking about is the exact same thing that other languages like C++ and D have. @Yukon, what do you mean by "registered"? You could always use one of the hallmarks of OOP and encapsulate such a method within its' own class. Thanks for contributing an answer to Stack Overflow! But it should also be local to the function that uses it. These are local to the block, and their default value is always zero. But see, in the first place you name this field in a self documenting way, to let it be known that it's to be used by that method alone. Find centralized, trusted content and collaborate around the technologies you use most. Same variables may be used in different functions such as function() { int a,b; function 1(); } function2 () { int a=0; b=20; } Global variable:-the variables that are defined outside of the . And then you browse the members of your class, and the list is clogged by half of them that are state private fields used by one method alone each, that should be static local variables, not appearing in the list of class members. I could also keep Where would these static variables in C#. and a new one should be started that perhapscontains a link to the old one to provide context for the discussion. Their values then persist between invocations. Tabularray table when is wraped by a tcolorbox spreads inside right margin overrides page borders. I can't do that, I could use a variable with class-level scope (global). But I'm not talking about global variables at all. You can initialize it with an initializer or a static constructor. Edit: This SO answer is very informative too. Hmm, that's helpful. If you wish for other code to be able modify it while your method executes, this feature, there is no good reason not to have it. It would be better to implement the pointer-based approach like this: Now, B::~B() will be invoked (if applicable) and that memory will be correctly removed when b is destroyed, and the lifetime is the same as your first example. Now let us understand static variables. The problem will turn into a murder mystery, a "whodunit.". A local variable in a function or static local variable: Visibility is the same as the automatic local variables. That was myoriginal response, and it still is. It is poor OO software design. Where would these static variables For example, we can use static int to count a number of times a . Also, the compiler can take advantage of that new information and optimize it away in some situations, depending on the specific type you are dealing with. A static variable has local scope, but is also preserved for as long as the program runs. Say you have a doSomething() method in your class, and you use a field, say int doSomethingCount to count how many times this one method was called. I do not see howthis offers any advantages over what is currently available. Something can be done or not a fit? mean that everyone else does. it and the world hasn't ended because of it. What is the difference between 'typedef' and 'using' in C++11? Would salt mines, lakes or flats be reasonably found in high, snowy elevations? Then again, variables are normally stored elsewhere, within the class'type object along with the compiled methods. Using "static variables" lets you retain the value of a variable that may go in and out of scope during execution, yet remain valid.A static variable has the scope of a local variable although the lifetime of a module level variable. He didn't ask how YOU write code, he asked how to do static locals The static variable may be internal or external depending on the place of declaration. In line 4, a and b are declared as two global variables of type int.The variable a will be automatically initialized to 0. iii. We have called the increase function twice in the main method and on the second call, the output is . This thread was a question, not a discussion. Obviously, they would have to be stored in some fashion on the Managed Heap with the object instance, in a fashion identical to an instance variable. Thank-you. When to implement a static local variable as a hidden instance field or a hidden static field? Youll be auto redirected in 1 second. variable_name This is the name of variable given by user. Now, I can see how this can be a huge burden for garbage collection. Prefixtablenameswithdefaultschemaname if set, //staticregexdefinedabove. Mathematica cannot find square roots of some matrices? The scope isn't as constrained as it was in 'C' but that shouldn't be a real problem. It's only the compiler that would have to be aware that static local variables have the same scope as fields, but visibility limited to one method. From the standard, section 6.2.4/3 Storage durations of objects: An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class . I don't see how that's anything like a global variable. 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