import "C"
func f() {
var vGo int
var vC C.int
// fails to compile with error
// cannot use &vGo (type *int) as type *C.int in argument to...
C.c_function(&vGo)
// compiles just fine:
C.c_function(&vC)
}
I compile with CGO_ENABLED=1 GOARCH=arm...
What's the different in int and C.int types in this case?
Where do I find additional information on C types in GO?
What's the difference between the types? It depends. If you're on 64bit, the Go int will be 64 bits while the C int will be 32. If you're on 32bit, there is no real difference.
Where do I find additional information on C types in Go? Look at documentation for C. As mentioned in the comments, implicit numeric type conversions aren't allowed in Go so a conversion is required.
Go deliberately does not support implicit type conversion, with some exceptions1:
A value x is assignable to a variable of type T ("x is assignable to T") in any of these cases:
- x's type is identical to T.
- x's type V and T have identical underlying types and at least one of V or T is not a named type.
- T is an interface type and x implements T.
- x is a bidirectional channel value, T is a channel type, x's type V and T have identical element types, and at least one of V or T is not a named type.
- x is the predeclared identifier nil and T is a pointer, function, slice, map, channel, or interface type.
- x is an untyped constant representable by a value of type T.
The conversion in your case is needed to match potentially different memory layouts2.