Identifying Low-Memory Situations

No matter how efficiently you allocate memory and how efficiently your application uses RAM, your device might run low on memory. At a programming level, a low-memory situation can manifest itself to the application in the following ways:

• A call to VirtualAlloc returns a 0, indicating that the function failed to allocate memory.
• Either LocalAlloc or HeapAlloc returns a 0, indicating that an attempt to increase the size of a heap has failed.
• Windows CE returns a stack fault error to your application, indicating that a stack allocation has failed.

Note Low-memory situations may be caused indirectly. For example, a call to the CreateWindow function can cause these types of memory failures.

To avoid the problems associated with low memory, Windows CE constantly monitors the amount of memory that is available and tries to prevent low-memory situations from occurring. It does this in several ways:

• When an application attempts to allocate memory, Windows CE filters the request. Filtering prevents a single application from using all of the available memory with one large allocation by lowering the maximum allocation limit.
• When Windows CE enters a low-memory situation, it lowers the memory limit further.

To recognize a low-memory situation, monitor the return values for your memory allocation functions. The platform you program on may also have additional functions to help you deal with low-memory situations. For more information, see the platform-specific documentation.