C++结构体内存对齐跨平台测试
测试1，不规则对齐数据。
Code:
#include <stdio.h> #pragma pack(push)
#pragma pack(8)
struct Test8
{
char a;
long long b;
char d;
};
#pragma pack(pop) #pragma pack(push)
#pragma pack(4)
struct Test4
{
char a;
long long b;
char d;
};
#pragma pack(pop) #pragma pack(push)
#pragma pack(1)
struct Test1
{
char a;
long long b;
char d;
};
#pragma pack(pop) struct Test0
{
char a;
long long b;
char d;
}; int main()
{
printf("sizeof(void*)=%d\n", sizeof(void*));
printf("sizeof(long long)=%d\n", sizeof(long long));
printf("sizeof(Test8)=%d\n", sizeof(struct Test8));
printf("sizeof(Tes4)=%d\n", sizeof(struct Test4));
printf( "sizeof(Test1)=%d\n", sizeof(struct Test1));
printf("sizeof(Test0)=%d\n", sizeof(struct Test0)); return ;
}
Output msvc x86:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
Output msvc x64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
Output xcode IOS armV7:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
Output xcode IOS arm64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
Android armv7 simulator output code:
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(void*)=%d\n", sizeof(void*));
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(long long)=%d\n", sizeof(long long));
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(Test8)=%d\n", sizeof(Test8));
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(Tes4)=%d\n", sizeof(Test4));
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(Test1)=%d\n", sizeof(Test1));
__android_log_print(ANDROID_LOG_DEBUG, "JNITag", "sizeof(Test0)=%d\n", sizeof(Test0));
Android armv7 simulator Output:
D/JNITag: sizeof(void*)=
D/JNITag: sizeof(long long)=
D/JNITag: sizeof(Test8)=
D/JNITag: sizeof(Tes4)=
D/JNITag: sizeof(Test1)=
D/JNITag: sizeof(Test0)=
测试二，简单数组测试，源码：
#include <stdio.h> #pragma pack(push)
#pragma pack(8)
struct Test8
{
char a[];
};
#pragma pack(pop) #pragma pack(push)
#pragma pack(4)
struct Test4
{
char a[];
};
#pragma pack(pop) #pragma pack(push)
#pragma pack(1)
struct Test1
{
char a[];
};
#pragma pack(pop) struct Test0
{
char a[];
}; int main()
{
printf("sizeof(void*)=%d\n", sizeof(void*));
printf("sizeof(long long)=%d\n", sizeof(long long));
printf("sizeof(Test8)=%d\n", sizeof(struct Test8));
printf("sizeof(Tes4)=%d\n", sizeof(struct Test4));
printf( "sizeof(Test1)=%d\n", sizeof(struct Test1));
printf("sizeof(Test0)=%d\n", sizeof(struct Test0)); return ;
}
msvc x86:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
msvc x64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test1)=
iphone armv7:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
iphone arm64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test8)=
sizeof(Tes4)=
sizeof(Test1)=
sizeof(Test0)=
android armv7 simulator:
D/JNITag: sizeof(void*)=
D/JNITag: sizeof(long long)=
D/JNITag: sizeof(Test8)=
D/JNITag: sizeof(Tes4)=
D/JNITag: sizeof(Test1)=
D/JNITag: sizeof(Test0)=
测试三，当结构体包含pack1的结构体时
code：
#include <stdio.h>
#include <stddef.h> #pragma pack(push)
#pragma pack(1)
struct Test1
{
char a[];
long long b;
char d[];
int e;
};
#pragma pack(pop) #pragma pack(push)
#pragma pack(8)
struct Owner8
{
char c1;
struct Test1 a;
int i2;
}; #pragma pack(pop) #pragma pack(push)
#pragma pack(4)
struct Owner4
{
char c1;
struct Test1 a;
int i2;
}; #pragma pack(pop) #pragma pack(push)
#pragma pack(1)
struct Owner1
{
char c1;
struct Test1 a;
int i2;
}; #pragma pack(pop) struct Owner0
{
char c1;
struct Test1 a;
int i2;
}; int main()
{
printf("sizeof(void*)=%d\n", sizeof(void*));
printf("sizeof(long long)=%d\n", sizeof(long long));
printf( "sizeof(Test1)=%d\n", sizeof(struct Test1)); printf("---------------------------------------\n");
printf("sizeof(Owner8)=%d\n", sizeof(struct Owner8));
printf("offsetof(Owner8, a)=%d\n", offsetof( struct Owner8, a));
printf("offsetof(Owner8, i2)=%d\n", offsetof( struct Owner8, i2)); printf("---------------------------------------\n");
printf("sizeof(Owner4)=%d\n", sizeof(struct Owner4));
printf("offsetof(Owner4, a)=%d\n", offsetof( struct Owner4, a));
printf("offsetof(Owner4, i2)=%d\n", offsetof( struct Owner4, i2)); printf("---------------------------------------\n");
printf("sizeof(Owner1)=%d\n", sizeof(struct Owner1));
printf("offsetof(Owner1, a)=%d\n", offsetof( struct Owner1, a));
printf("offsetof(Owner1, i2)=%d\n", offsetof( struct Owner1, i2)); printf("---------------------------------------\n");
printf("sizeof(Owner0)=%d\n", sizeof(struct Owner0));
printf("offsetof(Owner0, a)=%d\n", offsetof( struct Owner0, a));
printf("offsetof(Owner0, i2)=%d\n", offsetof( struct Owner0, i2)); return ;
}
msvc x86:
sizeof(void*)=
sizeof(long long)=
sizeof(Test1)=
---------------------------------------
sizeof(Owner8)=
offsetof(Owner8, a)=
offsetof(Owner8, i2)=
---------------------------------------
sizeof(Owner4)=
offsetof(Owner4, a)=
offsetof(Owner4, i2)=
---------------------------------------
sizeof(Owner1)=
offsetof(Owner1, a)=
offsetof(Owner1, i2)=
---------------------------------------
sizeof(Owner0)=
offsetof(Owner0, a)=
offsetof(Owner0, i2)=
msvc x64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test1)=
---------------------------------------
sizeof(Owner8)=
offsetof(Owner8, a)=
offsetof(Owner8, i2)=
---------------------------------------
sizeof(Owner4)=
offsetof(Owner4, a)=
offsetof(Owner4, i2)=
---------------------------------------
sizeof(Owner1)=
offsetof(Owner1, a)=
offsetof(Owner1, i2)=
---------------------------------------
sizeof(Owner0)=
offsetof(Owner0, a)=
offsetof(Owner0, i2)=
xcode ios armv7:
sizeof(void*)=
sizeof(long long)=
sizeof(Test1)=
---------------------------------------
sizeof(Owner8)=
offsetof(Owner8, a)=
offsetof(Owner8, i2)=
---------------------------------------
sizeof(Owner4)=
offsetof(Owner4, a)=
offsetof(Owner4, i2)=
---------------------------------------
sizeof(Owner1)=
offsetof(Owner1, a)=
offsetof(Owner1, i2)=
---------------------------------------
sizeof(Owner0)=
offsetof(Owner0, a)=
offsetof(Owner0, i2)=
xcode ios arm64:
sizeof(void*)=
sizeof(long long)=
sizeof(Test1)=
---------------------------------------
sizeof(Owner8)=
offsetof(Owner8, a)=
offsetof(Owner8, i2)=
---------------------------------------
sizeof(Owner4)=
offsetof(Owner4, a)=
offsetof(Owner4, i2)=
---------------------------------------
sizeof(Owner1)=
offsetof(Owner1, a)=
offsetof(Owner1, i2)=
---------------------------------------
sizeof(Owner0)=
offsetof(Owner0, a)=
offsetof(Owner0, i2)=
android armv7 simulator:
D/JNITag: sizeof(void*)=
D/JNITag: sizeof(long long)=
D/JNITag: sizeof(Test1)=
D/JNITag: ---------------------------------------
D/JNITag: sizeof(Owner8)=
D/JNITag: offsetof(Owner8, a)=
D/JNITag: offsetof(Owner8, i2)=
D/JNITag: ---------------------------------------
D/JNITag: sizeof(Owner4)=
D/JNITag: offsetof(Owner4, a)=
D/JNITag: offsetof(Owner4, i2)=
D/JNITag: ---------------------------------------
D/JNITag: sizeof(Owner1)=
D/JNITag: offsetof(Owner1, a)=
D/JNITag: offsetof(Owner1, i2)=
D/JNITag: ---------------------------------------
D/JNITag: sizeof(Owner0)=
D/JNITag: offsetof(Owner0, a)=
D/JNITag: offsetof(Owner0, i2)=
C++结构体内存对齐跨平台测试的更多相关文章
- C++ struct结构体内存对齐
•小试牛刀 我们自定义两个结构体 A 和 B: struct A { char c1; char c2; int i; double d; }; struct B { char c1; int i; ...
- 【APUE】Chapter17 Advanced IPC & sign extension & 结构体内存对齐
17.1 Introduction 这一章主要讲了UNIX Domain Sockets这样的进程间通讯方式,并列举了具体的几个例子. 17.2 UNIX Domain Sockets 这是一种特殊s ...
- 关于结构体内存对齐方式的总结（#pragma pack()和alignas()）
最近闲来无事,翻阅msdn,在预编译指令中,翻阅到#pragma pack这个预处理指令,这个预处理指令为结构体内存对齐指令,偶然发现还有另外的内存对齐指令aligns(C++11),__declsp ...
- [C/C++] 结构体内存对齐用法
一.为什么要内存对齐 经过内存对齐之后,CPU的内存访问速度大大提升; 内存空间按照byte划分,从理论上讲似乎对任何类型的变量的访问可以从任何地址开始,但实际情况是在访问特定变量的时候经常在特定的内 ...
- [C/C++] 结构体内存对齐：alignas alignof pack
简述: alignas(x):指定结构体内某个成员的对齐字节数,指定的对齐字节数不能小于它原本的字节数,且为2^n; #pragma pack(x):指定结构体的对齐方式,只能缩小结构体的对齐数,且为 ...
- go语言结构体内存对齐
cpu要想从内存读取数据,需要通过地址总线,把地址传输给内存,内存准备好数据,输出到数据总线,交给cpu,如果地址总线只有8根,那这个地址就只有8位可以表示[0,255]256个地址,因为表示不了更多 ...
- C语言-结构体内存对齐
C语言结构体对齐也是老生常谈的话题了.基本上是面试题的必考题.内容虽然很基础,但一不小心就会弄错.写出一个struct,然后sizeof,你会不会经常对结果感到奇怪?sizeof的结果往往都比你声明的 ...
- c 结构体内存对齐详解
0x00简介 首先要知道结构体的对齐规制 1.第一个成员在结构体变量偏移量为0的地址处 2.其他成员变量对齐到某个数字的整数倍的地址处 对齐数=编辑器默认的一个对齐数与该成员大小的较小值 vs中默认的 ...
- C语言中结构体内存对齐
先写一个小程序: #include<stdio.h> struct student { int a; char k; short m; }; int main() { st ...
随机推荐
- Java集合之HashSet
1.HashSet概述: HashSet实现Set接口,由哈希表(实际上是一个HashMap实例)支持.它不保证set 的迭代顺序:特别是它不保证该顺序恒久不变.此类允许使用null元素.HashSe ...
- Tomcat部署web项目,如何直接通过域名访问,不加项目名称
问题:下面的问题是互联网上问得比较多的,但是显然都是同一个问题. JavaWeb项目部署到tomcat服务之后设置不需要输入项目名称即可访问? Tomcat部署web项目,如何直接通过域名访问,不加项 ...
- [.net core]简介(转)
原文地址:https://docs.microsoft.com/zh-cn/dotnet/articles/core/ NET Core 是一个通用开发平台,由 Microsoft 和 GitHub ...
- java发送 email
public class EmailUtils implements IAction { private static Logger logger = Logger.getLogger(EmailUt ...
- Apache Torque入门学习
Introduction Apache Torque is an object-relational mapper for java. In other words, Torque lets you ...
- Alpha阶段项目总结
1.我们的软件要解决什么问题?是否定义得很清楚?是否对典型用户和典型场景有清晰的描述? 我们的软件是一款面向高校学生的简单快速的云笔记,不仅具有笔记的添加.修改.查看和删除功能,还有笔记公开功能,用户 ...
- svn检出的时候报 Unable to connect to a repository at URL错误（摘自CSDN）
背景:1. SVN服务器:VisualSVN-Server-2.5.5: 2. SVN客户端:TortoiseSVN-1.7.6.22632-x64-svn-1.7.4.msi: 在S ...
- CSS Sprites优缺点
利用CSS Sprites能很好地减少网页的http请求,从而大大的提高页面的性能,这也是CSS Sprites最大的优点,也是其被广泛传播和应用的主要原因: CSS Sprites能减少图片的字节, ...
- python 解压 压缩包
转 http://m.blog.csdn.net/blog/wice110956/26597179# 这里讨论使用Python解压如下五种压缩文件: .gz .tar .tgz .zip .rar ...
- 数据库阿里连接池 druid配置详解
http://blog.csdn.net/hj7jay/article/details/51686418 http://lj6684.iteye.com/blog/1770093 http://www ...