allocationat

Allocationat refers to a memory allocation operation that attempts to place a newly allocated block at a specified address within a process’s virtual address space. In contrast to conventional allocators that return any suitable free region, an allocationat request specifies a starting address and asks the allocator to honor that target if possible.

Semantics and parameters

An allocationat call typically supplies a target address, a size, and optionally an alignment requirement. The allocator may succeed by reserving and returning a pointer equal to the target address, or it may fail if the region is unavailable or if the request conflicts with protection, fragmentation, or platform constraints. Some implementations may allow a fallback behavior, returning a block at a nearby address while still attempting to respect alignment and size constraints. The exact contract can vary by language, runtime, and allocator.

Use cases and benefits

Fixed-address allocations are used in scenarios requiring interoperability with hardware buffers, memory-mapped I/O, or shared memory between processes, where the location of memory must be known in advance. They can also aid performance tuning by ensuring proximity to other objects or by reserving memory in a region with favorable characteristics. However, these benefits come with portability and safety trade-offs.

Limitations and considerations

Allocators that support allocationat are not universal, and fixed-address allocations can complicate memory management, increasing fragmentation risk and reducing address space layout randomization. They may require special permissions, platform-specific APIs, or cooperative policies across threads and components. Misuse can lead to aliasing hazards, crashes, or security vulnerabilities if assumptions about memory placement are violated.

Relation to related concepts

Allocationat is related to general memory allocation and deallocation, placement (as in placement new in C++), and fixed-address or reserved-address strategies in operating systems and runtime libraries. It is typically implemented only by specialized allocators or memory managers and is not a standard feature of all programming environments.