相关疑难解决方法(0)

static_assert(sizeof(unsigned) == 4, ":(");
static_assert(sizeof(double) == 8 ,":(");
unsigned u{42};
double x{u};

g ++ 4.7.1抱怨这段代码:

warning: narrowing conversion of 'u' from 'unsigned int' to 'double' inside { }

为什么这是一个缩小的转换？是不是每个人都能unsigned完美代表double？