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The static keyword (static and extern are mutually exclusive), applied to the definition of an external variable, changes this a bit: the variable can only be accessed by the functions in the same module where it was defined. But it is possible for a function in the same module to pass a reference (pointer) of the variable to another function ...
C++ is also more strict in conversions to enums: ints cannot be implicitly converted to enums as in C. Also, enumeration constants (enum enumerators) are always of type int in C, whereas they are distinct types in C++ and may have a size different from that of int. [needs update] In C++ a const variable must be initialized; in C this is not ...
const - Specifies that a variable is a constant value that has to be initialized when it gets declared. event - Declares an event. extern - Specifies that a method signature without a body uses a DLL-import. override - Specifies that a method or property declaration is an override of a virtual member or an implementation of a member of an ...
C++ generally prohibits forward references, but they are allowed in the special case of class members. Since the member function accessor cannot be compiled until the compiler knows the type of the member variable myValue, it is the compiler's responsibility to remember the definition of accessor until it sees myValue's declaration.
Such extern declarations are often placed in a shared header file, since it is common practice for all .c files in a project to include at least one .h file: the standard header file errno.h is an example, making the errno variable accessible to all modules in a project.
This typically occurs if a header file is included twice by the same source file without appropriate header guards. class C {}; // first definition of C class C {}; // error, second definition of C In the following, forming a pointer to S or defining a function taking a reference to S are examples of legal constructs, because they do not ...
Information hiding is accomplished by furnishing a compiled version of the source code that is interfaced via a header file. Almost always, there is a way to override such protection – usually via reflection API (Ruby, Java, C#, etc.), sometimes by mechanism like name mangling , or special keyword usage like friend in C++.
The _Thread_local (thread_local in C++, and in C since C23, and in earlier versions of C if the header <threads.h> is included) storage class specifier, introduced in C11, is used to declare a thread-local variable. It can be combined with static or extern to determine linkage.