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src/site/notes/ProgrammingLanguages/cpp/build-set/gcc/gcc attributes.md

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+---
+{"dg-publish":true,"permalink":"/ProgrammingLanguages/cpp/build-set/gcc/gcc attributes/","noteIcon":"3"}
+---
+
+https://stackoverflow.com/questions/11770451/what-is-the-meaning-of-attribute-packed-aligned4
+
+#gcc #attributes #cling
+### 1. alignment
+
+```cpp
+// 注意cling一行一行解析，这里对于结构体定义的大括号需要在同一行
+struct sSampleStruct1 {
+     char Data1;
+     //3-Bytes Added here.
+     int Data2;
+     unsigned short Data3;
+     char Data4;
+     //1-byte Added here.
+};
+
+struct sSampleStruct2 {
+     char Data1;
+     int Data2;
+     unsigned short Data3;
+     char Data4;
+
+}__attribute__((packed, aligned(1)));
+
+cout<<sizeof(sSampleStruct1)<<endl; // output: 12
+cout<<sizeof(sSampleStruct2)<<endl; // output: 8
+```
+
+
+
+