No, it could not. The controlling expression of any kind of conditional statement in C can be an integer. The return type of a function which returns boolean, t

No, it could not. The controlling expression of any kind of conditional statement in C can be an integer. The return type of a function which returns boolean, though, should be boolean. The strict requirement in the standard is just a 'scalar type': every conditional expression in C, even `if (true)`, technically evaluates on unequal comparison to zero. See section 6.8.4.1 "The if statement" of the standard: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf This applies to ternary operators, if statements, do/while loops, for loop termination conditions, etc. However, when defining a function that returns boolean, you've asked the compiler to make your program more strict than just returning an integer that's zero or nonzero, you're not allowed to return anything but 'true' or 'false' - no, you're not allowed to pack in error codes after the fact!