不同类型sizeof相关:
class A {};
class B { char m_data;};
class C {
char m_data[100];
};
class D {
char* m_data;
D() : m_data(new char[100]) {}
~D() { delete [] m_data;}
};
static void testSizeof() {
std::cout << "bool sizeof " << sizeof(bool) << std::endl; // 1
std::cout << "char sizeof " << sizeof(char) << std::endl; // 1
std::cout << "int sizeof " << sizeof(int) << std::endl; // 4
char data[10];
char* pData = data;
std::cout << "char data[10] sizeof " << sizeof(data) << std::endl; // 10
std::cout << "char* sizeof " << sizeof(pData) << std::endl; // 4 8
std::cout << "A sizeof " << sizeof(A) << std::endl; // 1
std::cout << "B sizeof " << sizeof(B) << std::endl; // 1 成员变量的大小
std::cout << "C sizeof " << sizeof(C) << std::endl; // 100
std::cout << "D sizeof " << sizeof(D) << std::endl; // 8 一个指针大小的成员变量
std::cout << "size_t sizeof " << sizeof(std::size_t) << std::endl; // 8
}
//有符号数与无符号数进行比较,有符号数会先转换成无符号数再比较,-1会转换成无符号最大的那个数:
static void unsignedAndSigned() {
std::size_t a = 10;
int b = -1;
if (b < a)
std::cout << "right\n";
else
std::cout << "bad\n";
}