Why do I get these warnings in Visual C++ 2008 when building a struct?

I have this code

typedef struct
{
    const char* fooString;
    const bool  fooBool;
}fooStruct;

And this initializer:

static const fooStruct foo[] =
{
    {"file1", true},
    {"file2", false},
    ....
};

With this code I have 3 warnings in VS2008:

error C2220: warning treated as error - no 'object' file generated  
warning C4510: '<unnamed-tag>' : default constructor could not开发者_运维问答 be generated
warning C4512: '<unnamed-tag>' : assignment operator could not be generated
warning C4610: struct '<unnamed-tag>' can never be instantiated - user defined constructor required 

It's exactly what the compiler says: it can't generate a default constructor or assignment operator for your struct because it has a const member in it (const bool fooBool). struct members which are const or which are references cannot be default-initialized, so they must be explicitly initialized in a user-written constructor or assignment operator.

One solution is to write your own default constructor and assignment operator (and in line with the rule of three, you should also write a copy constructor; a destructor isn't strictly necessary but is good practice). The alternative, easier solution is just to make fooBool non-const. Then, the compiler will happily generate the default constructor and assignment operator for you.

Since you're already creating an array of const instances of these with static const fooStruct foo[] = ..., the extra const on fooBool is pointless.

The C4610 warning is incorrect. This is a known bug in Visual C++. See the Microsoft Connect bug "Improper issuance of C4610."

Adam Rosenfield explains why the other two warnings (C4510 and C4512) are emitted.

Also if you do partial initialization then MSVC2008 will throw errors (as does MSVC2010) which is incorrect behavior as defined by C++03 and C++11. I posted more on this in another thread on stack overflow which you can read here

// Partial initialization, leaving it to the compiler
// to do aggregate value-initialization
fooStruct foo ={"file1", /*missing true/false, compiler should set false*/ };

MSVC will throw an error on this code along with the warnings you mentioned.