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Are static variables automatically initialized?
Global and static variables are initialized to their default values because it is in the C or C++ standards and it is free to assign a value by zero at compile time. Both static and global variable behave same to the generated object code. These variables are allocated in .
Where are static variables initialized?
Static variables are initialized only once , at the start of the execution. These variables will be initialized first, before the initialization of any instance variables. A single copy to be shared by all instances of the class. A static variable can be accessed directly by the class name and doesn’t need any object.
Can static variables be initialized twice?
a , so ClassA.o initialization code is run before main() . When the first function in the dynamic libB.so is accessed, all initializers for libB.so are run. Since libB.so includes ClassA.o , ClassA.o ‘s static initializer must be run (again).
Are static variables initialized at compile time?
In an ideal world all static variables are const-initialized. If the initial value of a static variable can’t be evaluated at compile time, the compiler will perform zero-initialization. Hence, during static initialization all static variables are either const-initialized or zero-initialized.
Why static variables are initialized only once?
When static keyword is used, variable or data members or functions can not be modified again. Static variables are initialized only once. Compiler persist the variable till the end of the program. Static variable can be defined inside or outside the function.
How to initialize a static variable in a library?
Then in the header for the library declare a static variable that is initialized by calling the global function: Every compilation unit that includes the header will have a static variable that needs to be initialized by calling a (useless) function in the library.
Is it possible to rely on static initialization order?
You cannot rely on static initialization order except to the extent that: Static variables defined in a translation unit will be initialized before any function or method in that translation unit is invoked for the first time.
When to initialize a static variable in a translation unit?
Static variables defined in a translation unit will be initialized before any function or method in that translation unit is invoked for the first time. What you cannot rely on is that a static variable will be initialized before a function or method in some other translation unit is invoked for the first time.
What happens when I link to a static library?
When you are linking with a static library, you are in fact extracting from it the object files which provide symbols which are currently used but not defined. In the pattern that you are using, there is probably no undefined symbols provided by the object file which contains the static variable which triggers registration.