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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