A lot of ICU implementation code writes strings and other contents to buffers that require a fair bit of boilerplate memory management. Usually, a fixed-length stack buffer is used to cover the most common cases. An initial guess for the needed capacity may exceed the stack buffer size, requiring immediate heap allocation. An overflow may occur during processing, requiring heap allocation or reallocation, with or without copying the current contents. Some functions need a destination buffer with the same capacity as one provided on input, such as string case mapping functions when source and destination are the same buffer. When the function exits, a heap-allocated buffer must be freed, and there might be several exit points from the function.