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 0; }
Output msvc x86:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test8)=24 sizeof(Tes4)=16 sizeof(Test1)=10 sizeof(Test0)=24
Output msvc x64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test8)=24 sizeof(Tes4)=16 sizeof(Test1)=10 sizeof(Test0)=24
Output xcode IOS armV7:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test8)=16 sizeof(Tes4)=16 sizeof(Test1)=10 sizeof(Test0)=16
Output xcode IOS arm64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test8)=24 sizeof(Tes4)=16 sizeof(Test1)=10 sizeof(Test0)=24
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*)=4 D/JNITag: sizeof(long long)=8 D/JNITag: sizeof(Test8)=16 D/JNITag: sizeof(Tes4)=16 D/JNITag: sizeof(Test1)=10 D/JNITag: sizeof(Test0)=16
测试二，简单数组测试，源码：
#include <stdio.h> #pragma pack(push) #pragma pack(8) struct Test8 { char a[3]; }; #pragma pack(pop) #pragma pack(push) #pragma pack(4) struct Test4 { char a[3]; }; #pragma pack(pop) #pragma pack(push) #pragma pack(1) struct Test1 { char a[3]; }; #pragma pack(pop) struct Test0 { char a[3]; }; 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 0; }
msvc x86:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test8)=3 sizeof(Tes4)=3 sizeof(Test1)=3 sizeof(Test0)=3
msvc x64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test8)=3 sizeof(Tes4)=3 sizeof(Test1)=3 sizeof(Test1)=3
iphone armv7:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test8)=3 sizeof(Tes4)=3 sizeof(Test1)=3 sizeof(Test0)=3
iphone arm64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test8)=3 sizeof(Tes4)=3 sizeof(Test1)=3 sizeof(Test0)=3
android armv7 simulator:
D/JNITag: sizeof(void*)=4 D/JNITag: sizeof(long long)=8 D/JNITag: sizeof(Test8)=3 D/JNITag: sizeof(Tes4)=3 D/JNITag: sizeof(Test1)=3 D/JNITag: sizeof(Test0)=3
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[3]; long long b; char d[2]; 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 0; }
msvc x86:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test1)=17 --------------------------------------- sizeof(Owner8)=24 offsetof(Owner8, a)=1 offsetof(Owner8, i2)=20 --------------------------------------- sizeof(Owner4)=24 offsetof(Owner4, a)=1 offsetof(Owner4, i2)=20 --------------------------------------- sizeof(Owner1)=22 offsetof(Owner1, a)=1 offsetof(Owner1, i2)=18 --------------------------------------- sizeof(Owner0)=24 offsetof(Owner0, a)=1 offsetof(Owner0, i2)=20
msvc x64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test1)=17 --------------------------------------- sizeof(Owner8)=24 offsetof(Owner8, a)=1 offsetof(Owner8, i2)=20 --------------------------------------- sizeof(Owner4)=24 offsetof(Owner4, a)=1 offsetof(Owner4, i2)=20 --------------------------------------- sizeof(Owner1)=22 offsetof(Owner1, a)=1 offsetof(Owner1, i2)=18 --------------------------------------- sizeof(Owner0)=24 offsetof(Owner0, a)=1 offsetof(Owner0, i2)=20
xcode ios armv7:
sizeof(void*)=4 sizeof(long long)=8 sizeof(Test1)=17 --------------------------------------- sizeof(Owner8)=24 offsetof(Owner8, a)=1 offsetof(Owner8, i2)=20 --------------------------------------- sizeof(Owner4)=24 offsetof(Owner4, a)=1 offsetof(Owner4, i2)=20 --------------------------------------- sizeof(Owner1)=22 offsetof(Owner1, a)=1 offsetof(Owner1, i2)=18 --------------------------------------- sizeof(Owner0)=24 offsetof(Owner0, a)=1 offsetof(Owner0, i2)=20
xcode ios arm64:
sizeof(void*)=8 sizeof(long long)=8 sizeof(Test1)=17 --------------------------------------- sizeof(Owner8)=24 offsetof(Owner8, a)=1 offsetof(Owner8, i2)=20 --------------------------------------- sizeof(Owner4)=24 offsetof(Owner4, a)=1 offsetof(Owner4, i2)=20 --------------------------------------- sizeof(Owner1)=22 offsetof(Owner1, a)=1 offsetof(Owner1, i2)=18 --------------------------------------- sizeof(Owner0)=24 offsetof(Owner0, a)=1 offsetof(Owner0, i2)=20
android armv7 simulator:
D/JNITag: sizeof(void*)=4 D/JNITag: sizeof(long long)=8 D/JNITag: sizeof(Test1)=17 D/JNITag: --------------------------------------- D/JNITag: sizeof(Owner8)=24 D/JNITag: offsetof(Owner8, a)=1 D/JNITag: offsetof(Owner8, i2)=20 D/JNITag: --------------------------------------- D/JNITag: sizeof(Owner4)=24 D/JNITag: offsetof(Owner4, a)=1 D/JNITag: offsetof(Owner4, i2)=20 D/JNITag: --------------------------------------- D/JNITag: sizeof(Owner1)=22 D/JNITag: offsetof(Owner1, a)=1 D/JNITag: offsetof(Owner1, i2)=18 D/JNITag: --------------------------------------- D/JNITag: sizeof(Owner0)=24 D/JNITag: offsetof(Owner0, a)=1 D/JNITag: offsetof(Owner0, i2)=20