1-OC对象本质

        NSObject* obj = [[NSObject alloc] init];
        Student* student = [[Student alloc]init];
        
        NSString* str = @"hello";
        
        student->_no = 25;
        student->_age = 30;
        
        NSLog(@"%zd",class_getInstanceSize([NSObject class]));
        
        NSLog(@"%zd",malloc_size((__bridge const void *)(obj)));
        
        NSLog(@"%zd",class_getInstanceSize([Student class]));
        
        NSLog(@"%zd",malloc_size(CFBridgingRetain(student)));
        
        NSLog(@"%zd",class_getInstanceSize([NSString class]));
        
        NSLog(@"%zd",malloc_size(CFBridgingRetain(str)));
        
        struct Student_IMPL * stu = (__bridge struct Student_IMPL *)student;
        
        NSLog(@"no is %d, age is %d",stu->_no,stu->_age);

1. lldb命令

• p(print)

image.png

• po(print object)

image.png

• x(memory read)

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• memory write

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2. 获取NSObject对象占用内存大小

• NSObject实例对象的成员变量大小

#import <objc/runtime.h>
NSLog(@"%zd",class_getInstanceSize([NSObject class]));     //8

• NSObject实例对象占用内存大小

#import <malloc/malloc.h>
NSLog(@"%zd",malloc_size((__bridge const void *)(obj)));    //16

3. 内存对齐

• 结构体的最终大小必须是最大成员大小的倍数，iOS都是分配16个字节的倍数