I tried to google for an answer but couldn't find anything. What is the
correct way to do the following on Linux?
@_silgen_name("foo")
func foo(theInt: UInt)
-> (a: UInt, b: UInt, c: UInt)
var (d, e, f) = foo(aNum)
Where foo is:
typedef struct {
long a;
long b;
long c;
} Tuple;
extern "C" {
Tuple foo(int i) {
return Tuple{ i, i, i };
}
}
Currently, the call to foo crashes because foo wants to return the tuple
indirectly, but the Swift call expects the three scalar return values in
registers. This example is a generalization of runtime functions such as
swift_class_getInstanceExtents, which happens to work because it only
returns two scalars in RAX and RDX, which is supported by Clang. But my
tests show that three-scalar tuples/structs will cause problems. On
architectures where Clang only supports one scalar return value, the
problem is worse.
Am I doing something wrong or is there already a way to deal with this
(e.g. annotation in Swift code to make it obey C ABI, or vice versa)?
Thanks, Bryan
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