What are the problems with dynamic memory allocation in embedded systems?

Dynamic allocation (malloc/free) is risky in embedded systems for several reasons:

• Fragmentation — repeated alloc/free cycles fragment the heap into small unusable blocks. With limited RAM, this causes allocation failures even when total free memory is sufficient.
• Non-deterministic timing — malloc execution time varies depending on heap state, violating real-time deadlines.
• No garbage collection — every leak is permanent. In a device running for years, even tiny leaks are fatal.
• Difficult to test — fragmentation failures depend on allocation patterns over time and are nearly impossible to reproduce.

Many embedded coding standards (MISRA C, NASA JPL, DO-178C) ban dynamic allocation entirely. Alternatives include static allocation, memory pools (fixed-size block allocators), and stack allocation for short-lived buffers.