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The program accesses this block of memory via a pointer that malloc returns. When the memory is no longer needed, the pointer is passed to free which deallocates the memory so that it can be used for other purposes. The original description of C indicated that calloc and cfree were in the standard library, but not malloc.
The C++ standard library instead provides a dynamic array (collection) that can be extended or reduced in its std::vector template class. The C++ standard does not specify any relation between new / delete and the C memory allocation routines, but new and delete are typically implemented as wrappers around malloc and free. [6]
mimalloc (pronounced "me-malloc") is a free and open-source compact general-purpose memory allocator developed by Microsoft [2] with focus on performance characteristics. The library is about 11000 lines of code and works as a drop-in replacement for malloc of the C standard library [3] and requires no additional code changes.
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++:
The standard C library provides the function malloc() for allocating memory blocks from the heap. It takes the size of an object to allocate as a parameter and returns a pointer to a newly allocated block of memory suitable for storing the object, or it returns a null pointer if the allocation failed.
C++ also supports malloc and free, ... Use of new returns an address to the allocated memory. The C++ Core Guidelines ... complex class in the C++ standard library ...
Another frequent source of dangling pointers is a jumbled combination of malloc() and free() library calls: a pointer becomes dangling when the block of memory it points to is freed. As with the previous example one way to avoid this is to make sure to reset the pointer to null after freeing its reference—as demonstrated below.
Dynamic memory allocation: blocks of memory of arbitrary size can be requested at run-time using library functions such as malloc from a region of memory called the heap; these blocks persist until subsequently freed for reuse by calling the library function realloc or free.