This diagnostic rule is based on the MISRA (Motor Industry Software Reliability Association) guidelines for software development.
The behavior is undefined when two objects are created, and they partially overlap each other in memory, and one of them is assigned or copied to the other.
This may happen, for example, when you use the 'memcpy' function. In this case the source's memory area overlaps with that of the receiver:
void func(int *x)
{
memcpy(x, x+2, 10 * sizeof(int));
}In this case, '(x+2)', a pointer to a data source, is offset from the destination by 8 bytes ('sizeof(int) * 2'). An attempt to copy 40 bytes to the destination from the source leads to a partial source memory area overlap.
To avoid this error, you can use a function, that is specifically intended for such cases – 'memmove'. Alternatively, you can adjust the offsets specified for the source and receiver, so that memory areas do not overlap.
The correct code:
void func(int *x)
{
memmove(x, x+2, 10 * sizeof(int));
}This diagnostic is classified as:
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