C / C++ compiler warnings: do you clean up all your code to remove them or leave them in?

typedef struct _X * X; // from external header, not 64-bit portable

#pragma warning( push )
#pragma warning( disable: 4312 ) // 64-bit portability warning
X x = reinterpret_cast< X >( 0xDDDDDDDD ); // we know X not 64-bit portable
#pragma warning( pop )