![]() In C, the library function malloc is used to allocate a block of memory on the heap. These limitations are avoided by using dynamic memory allocation, in which memory is more explicitly (but more flexibly) managed, typically by allocating it from the free store (informally called the "heap"), an area of memory structured for this purpose. ![]() ![]() In many situations the programmer requires greater flexibility in managing the lifetime of allocated memory. Automatic-allocated data cannot persist across multiple function calls, while static data persists for the life of the program whether it is needed or not. Neither static- nor automatic-duration memory is adequate for all situations. The lifetime of allocated memory can also cause concern. If the required size is not known until run-time (for example, if data of arbitrary size is being read from the user or from a disk file), then using fixed-size data objects is inadequate. For static-duration and automatic-duration variables, the size of the allocation must be compile-time constant (except for the case of variable-length automatic arrays ). Static-duration variables are allocated in main memory, usually along with the executable code of the program, and persist for the lifetime of the program automatic-duration variables are allocated on the stack and come and go as functions are called and return. The C programming language manages memory statically, automatically, or dynamically. Their performance varies in both execution time and required memory. Many different implementations of the actual memory allocation mechanism, used by malloc, are available. Still, there are several situations in which using new/ delete is not applicable, such as garbage collection code or performance-sensitive code, and a combination of malloc and placement new may be required instead of the higher-level new operator. ![]() The C++ programming language includes these functions however, the operators new and delete provide similar functionality and are recommended by that language's authors. C dynamic memory allocation refers to performing manual memory management for dynamic memory allocation in the C programming language via a group of functions in the C standard library, namely malloc, realloc, calloc, aligned_alloc and free. ![]()
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