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On many common platforms, this use of pointer punning can create problems if different pointers are aligned in machine-specific ways. Furthermore, pointers of different sizes can alias accesses to the same memory, causing problems that are unchecked by the compiler. Even when data size and pointer representation match, however, compilers can ...
When an aggregate is entirely composed of the same type of primitive, the aggregate may be called an array; in a sense, a multi-byte word primitive is an array of bytes, and some programs use words in this way. A pointer is a programming concept used in computer science to reference or point to a memory location that stores a value or an object.
In computer programming, an indirection (also called a reference) is a way of referring to something using a name, reference, or container instead of the value itself. The most common form of indirection is the act of manipulating a value through its memory address. For example, accessing a variable through the use of a pointer.
A pointer to a type that's large enough to fill a word will be a simple address, while a pointer such as char* or void* will be a wide pointer: a pair of the address of a word and the offset of a byte within that word. Converting between pointer types is therefore not necessarily a trivial operation and can lose information if done incorrectly.
C supports the use of pointers, a type of reference that records the address or location of an object or function in memory. Pointers can be dereferenced to access data stored at the address pointed to, or to invoke a pointed-to function. Pointers can be manipulated using assignment or pointer arithmetic. The run-time representation of a ...
Specifically, C allows a void* pointer to be assigned to any pointer type without a cast, while C++ does not; this idiom appears often in C code using malloc memory allocation, [9] or in the passing of context pointers to the POSIX pthreads API, and other frameworks involving callbacks. For example, the following is valid in C but not C++:
As the type of an object at its creation is known at compile time, constructors, and by extension copy constructors, cannot be virtual. Nonetheless, a situation may arise where a copy of an object needs to be created when a pointer to a derived object is passed as a pointer to a base object.
In 32.9.1-1, this section describes components that a C++ program can use to retrieve in one thread the result (value or exception) from a function that has run in the same thread or another thread. <hazard_pointer> Added in C++26. Provides std::hazard_pointer. <latch> Added in C++20. Provides std::latch, a single-use thread barrier. <mutex>