C++: can't static_cast from double* to int*

Question

When I try to use a static_cast to cast a double* to an int*, I get the following error:

invalid static_cast from type ‘double*’ to type ‘int*’

Answer 1

Floating point-to-integer conversion is supported, so int a = static_cast(5.2) is fine. However, it's a conversion - the underlying data types are completely incompatible. What you're asking is for the runtime to convert a pointer to an 8-byte structure to a pointer to a 4-byte structure, which it can't do in any meaningful way.

That having been said, if you really want to interpret your double as an integer, int* r = reinterpret_cast(p) will work fine.