Out of memory (OOM) is an exceptional system state where any further memory allocation requests may fail. Such allocation failures would crash the process or system if not handled properly, and they may also lead to an inconsistent program state that cannot be recovered easily. Current mechanisms for preventing such hazards highly rely on the manual effort of the programmers themselves. This paper studies the OOM issues of Rust, which is an emerging system programming language that stresses the importance of memory safety but still lacks handy mechanisms to handle OOM well. Even worse, Rust employs an infallible mode of memory allocations by default. As a result, the program written by Rust would simply abort itself when OOM occurs. Such crashes would lead to critical robustness issues for services or modules of operating systems. We propose OOM-Guard, a handy approach for Rust programmers to handle OOM. OOM-Guard is in nature a reservation-based approach that aims to convert the handlings of many possible failed memory allocations into handlings of a smaller number of reservations. In order to achieve efficient reservation, OOM-Guard incorporates a subtle cost analysis algorithm based on static analysis and a proxy allocator. We then apply OOM-Guard to two well-known Rust projects, Bento and rCore. Results show that OOM-Guard can largely reduce developers’ efforts for handling OOM and incurs trivial overhead in both memory space and execution time.