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Differences between C and C++ linkage and calling conventions can also have subtle implications for code that uses function pointers. Some compilers will produce non-working code if a function pointer declared extern "C" points to a C++ function that is not declared extern "C". [22] For example, the following code:
, depending on the compiler and used optimization level, the compiler may interpret the conditional as always true (because func can be seen as undefined from a standards point of view). [7] An alternative to the above construct is using a system API to check if func is defined (e.g. dlsym with RTLD_DEFAULT). The above check may also fail for ...
In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference.An object referenced only by weak references – meaning "every chain of references that reaches the object includes at least one weak reference as a link" – is considered weakly reachable, and can be treated as unreachable and ...
In the C++ programming language, a reference is a simple reference datatype that is less powerful but safer than the pointer type inherited from C.The name C++ reference may cause confusion, as in computer science a reference is a general concept datatype, with pointers and C++ references being specific reference datatype implementations.
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.
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C++ also provides constructors to initialize an object, but they are often not as convenient as the initializer list. However, C++03 allows initializer-lists only on structs and classes that conform to the Plain Old Data (POD) definition; C++11 extends initializer-lists, so they can be used for all classes including standard containers like std ...