This is how a lot of people initialize their plain old data structs.
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| struct MyStruct
{
double first;
int second;
char third[4];
};
MyStruct my;
memset(&my, 0, sizeof(my));
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That memset is a lot of typing. Isn’t there a simpler way?
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| MyStruct my1; // uninitialized
MyStruct my2 = { 2.0 }; // partially zero-initialized
MyStruct my3 = {}; // completely zero-initialized
MyStruct my4 = MyStruct(); // zero-initialized
MyStruct my5(); // function declaration (oops!)
MyStruct my6{}; // uniform initialization (C++11)
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Note the partial initialization of my2.
The remaining fields are zero-initialized.
My favorite way is my3. It almost looks like my6, but it doesn’t require C++11.
What about creating structs on the heap?
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| MyStruct* pMy1 = new MyStruct; // uninitialized
MyStruct* pMy2 = new MyStruct(); // zero-initialized
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Those parentheses make a huge difference!
Static data is always initialized.
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| static MyStruct s_my; // zero-initialized
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How about arrays?
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| MyStruct arr1[5]; // uninitialized
MyStruct arr2[5] = {}; // zero-initialized
MyStruct* arr3 = new MyStruct[5]; // uninitialized
MyStruct* arr4 = new MyStruct[5](); // zero-initialized
std::vector<MyStruct> vec(5); // zero-initialized
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Like all STL containers, std::vector always initializes its data.