forked from epagris/FreeRTOS-Kernel
* Heap improvements This commit makes the following improvements: 1. Add a check to heap_2 to track if a memory block is allocated to the application or not. The MSB of the size field is used for this purpose. The same check already exists in heap_4 and heap_5. This check prevents against double free. 2. Add a new flag configHEAP_CLEAR_MEMORY_ON_FREE to heap_2, heap_4 and heap_5. The application writer can set it to 1 in their FreeRTOSConfig.h to ensure that a block of memory allocated using pvPortMalloc is cleared (i.e. set to zero) when it is freed using vPortFree. If left undefined, configHEAP_CLEAR_MEMORY_ON_FREE defaults to 0 for backward compatibility. We recommend setting configHEAP_CLEAR_MEMORY_ON_FREE to 1 for better security. 3. Add a new API pvPortCalloc to heap_2, heap_4 and heap_5. This API has the following signature: void * pvPortCalloc( size_t xNum, size_t xSize ); It allocates memory for an array of xNum objects each of which is of xSize and initializes all bytes in the allocated storage to zero. If allocation succeeds, it returns a pointer to the lowest byte in the allocated memory block. On failure, it returns a null pointer. Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
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