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)=
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