Garbage-collected languages, such as Go, Java, and Python, manage memory dynamically and abstract the complexities of allocation and deallocation from the programmer. This system simplifies development by ensuring efficient memory allocation, automatic cleanup, and robust runtime mechanisms.
Memory Management in Garbage-Collected Languages
At runtime, the language’s allocator uses system calls like mmap (on Linux) or VirtualAlloc (on Windows) to request large chunks of memory from the operating system. This reserved memory forms the heap space, which the runtime manages for dynamic allocations. mmap is particularly useful because it supports allocating memory in page-sized units (commonly 4 KB), with the ability to dynamically map, unmap, and expand memory regions as needed.
Once memory is reserved, the runtime subdivides the heap to allocate space for objects or variables. For instance, in Python, memory for variables is allocated transparently, while Go provides constructs like make or new for dynamic allocations. In Java, memory is automatically assigned when using the new keyword. Unlike in C or C++, programmers do not explicitly allocate or free memory; instead, the runtime handles all memory management details.
To ensure memory is efficiently used, garbage collection periodically reclaims unused memory. This process might involve mark-and-sweep algorithms, which identify reachable objects and remove everything else, or generational garbage collection, which focuses on quickly collecting short-lived objects while preserving long-lived ones for less frequent cleanup.