C allows a void* pointer to be assigned to any pointer type without a cast, whereas C++ does not; this idiom appears often in C code using malloc memory allocation. For example, the following is valid in C but not C++:
void * ptr; int *i = ptr; /* Implicit conversion from void* to int* */ |
or similarly:
int *j = malloc ( sizeof ( int ) * 5); /* Implicit conversion from void* to int* */ |
In order to make the code compile in both C and C++, one must use an explicit cast:
void * ptr; int *i = ( int *) ptr; int *j = ( int *) malloc ( sizeof ( int ) * 5); |
Source:
http://en.wikipedia.org/wiki/Compatibility_of_C_and_C%2B%2B
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