May I initialize a global variable with the result of a function call?

Is the following code legal?

int add(int a, int b) {开发者_开发知识库 return a + b; }

int some_global_variable = add(1, 2);

int main() { /* ... */ }

Yes. Yes, it is.

Static initializers may call functions, as long as they're in scope.

[dcl.decl] (2003 wording, 8/2):

Initial values can also be specified in a declarator; initializers are discussed in 8.5 and 12.6.

[dcl.init] (2003 wording, 8.5/2):

Automatic, register, static, and external variables of namespace scope can be initialized by arbitrary expressions involving literals and previously declared variables and functions.

(Don't be misled by the lack of the static keyword, which has all sorts of meanings. Your variable myvar is declared at namespace scope, and thus has static storage duration.)