From the C99 standard (7.21.1/2): Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still … Read more
In the general case, yes, there will be problems. Both memcpy and memmove are bitwise operations with no further semantics. That might not be sufficient to move the object*, and it is clearly not enough to copy. In the case of the copy it will break as multiple objects will be referring to the same … Read more
With memcpy, the destination cannot overlap the source at all. With memmove it can. This means that memmove might be very slightly slower than memcpy, as it cannot make the same assumptions. For example, memcpy might always copy addresses from low to high. If the destination overlaps after the source, this means some addresses will … Read more
I’m not entirely surprised that your example exhibits no strange behaviour. Try copying str1 to str1+2 instead and see what happens then. (May not actually make a difference, depends on compiler/libraries.) In general, memcpy is implemented in a simple (but fast) manner. Simplistically, it just loops over the data (in order), copying from one location … Read more