It may (or may not) include global variable space (it's a matter of convention). Heap memory was simply the memory that was left over after the program was loaded and the Stack memory was allocated. It is a simple matter of a move operation and a decrement/increment operation on the Stack register. The speed of its allocation/deallocation is fast because it is strictly a last-in/first-out design. Stack memory is very much the consequence of usual CPU design. For instance, during an interrupt, the Stack was used to store various CPU registers, including Status (which indicates the results of an operation) and Program Counter (where was the CPU in the program when the interrupt occurred). The Stack was used as a way to implement the "Jump-Subroutine"-"Return" code pattern in assembly language, and also as a means to implement hardware-level interrupt handling. Stack memory is specifically the range of memory that is accessible via the Stack register of the CPU. Running out of heap memory can (will?) result in a std::bad_alloc. Heap memory almost always must be manually freed, though you should really use a smart pointer class or similar to avoid needing to remember to do so. In general, C++ objects allocated with new, or blocks of memory allocated with the likes of malloc end up on the heap. It's a serious thing to encounter, but you really shouldn't come across one unless you have a crazy recursive function or something similar. Running out of stack memory is called a Stack buffer overflow. However the stack is a limited resource, and shouldn't be used for anything large. Generally speaking, the stack is preferred as it is usually in the CPU cache, so operations involving objects stored on it tend to be faster. Rarely, if ever, would you consider any sort of manual stack manipulation from C++. The stack is really best understood from a low level and I'd recommend Art of Assembly - Passing Parameters on the Stack. (caveat - compiler optimizations and calling conventions all mean things aren't this simple) Likewise, the function can push locals onto the stack and pop them off it before returning from the function. The function then knows that the parameters it expects can be found on the end of the stack. The stack is very much like the std::stack class: you push parameters onto it and then call a function. The stack is also used to hold parameters passed to functions. In C++ the stack memory is where local variables get stored/constructed. So both stack and heap memory physically might be RAM or the disk? Then what is the reason where heap allocation seems to be slower than the stack counterpart?Īlso, the main program would be run in the stack or a heap?Īlso, what would happen if a process run out of the stack memory or heap memory allocated? Stack and heap memory is the abstraction over the memory model of the virtual memory ( which might swap memory between disk and RAM). Is stack and heap memory model a concept of operating system or computer architecture? So some of it might not follow stack and heap memory model or all of them follow it? After some research on internet, the most common answer is stack memory is temporary and heap memory is permanent. If if create local variables, I would get memory from stack. All I know is when I call new, I would get memory from heap. I am programming in C++ and I am always wondering what exactly is stack memory vs heap memory.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |