CODEWITHSUNDEEP
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Felix Markov
Felix Markov

Reputation: 143

Keyword struct before constructor name

I was amazed when I saw that this code success compiled with MS Visual C++.

struct foo {
    struct foo(int i): value(i) {}
    int value;
};

What means keyword struct in such strange context?

Upvotes: 9

Views: 165

Answers (1)

Mike Seymour
Mike Seymour

Reputation: 254441

In most contexts, you can use the elaborated type specifier struct foo, or equivalently class foo, instead of just the class name foo. This can be useful to resolve ambiguities:

struct foo {};  // Declares a type
foo foo;        // Declares a variable with the same name

foo bar;        // Error: "foo" refers to the variable
struct foo bar; // OK: "foo" explicitly refers to the class type

However, you can't use this form when declaring a constructor, so your compiler is wrong to accept that code. The specification for a constructor declaration (in C++11 12.1/1) only allows the class name itself, not an elaborated type specifier.

In general, you shouldn't be surprised when Visual C++ compiles all kinds of wonky code. It's notorious for its non-standard extensions to the language.

Upvotes: 10

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