cgo: add support for bitfields using generated getters and setters

testdata/cgo/main.c

@@ -18,6 +18,7 @@ short globalArray[3] = {5, 6, 7};
 joined_t globalUnion;
 int globalUnionSize = sizeof(globalUnion);
 option_t globalOption = optionG;
+bitfield_t globalBitfield = {244, 15, 1, 2, 47, 5};
 
 int fortytwo() {
 	return 42;

testdata/cgo/main.go

@@ -64,6 +64,11 @@ func main() {
 	println("union global data:", C.globalUnion.data[0], C.globalUnion.data[1], C.globalUnion.data[2])
 	println("union field:", printUnion(C.globalUnion).f)
 	var _ C.union_joined = C.globalUnion
+	printBitfield(&C.globalBitfield)
+	C.globalBitfield.set_bitfield_a(7)
+	C.globalBitfield.set_bitfield_b(0)
+	C.globalBitfield.set_bitfield_c(0xff)
+	printBitfield(&C.globalBitfield)
 
 	// elaborated type
 	p := C.struct_point{x: 3, y: 5}
@@ -108,3 +113,11 @@ func printUnion(union C.joined_t) C.joined_t {
 func mul(a, b C.int) C.int {
 	return a * b
 }
+
+func printBitfield(bitfield *C.bitfield_t) {
+	println("bitfield a:", bitfield.bitfield_a())
+	println("bitfield b:", bitfield.bitfield_b())
+	println("bitfield c:", bitfield.bitfield_c())
+	println("bitfield d:", bitfield.d)
+	println("bitfield e:", bitfield.e)
+}

testdata/cgo/main.h

@@ -65,6 +65,17 @@ typedef enum {
 	option3A = 21,
 } option3_t;
 
+typedef struct {
+	unsigned char start;
+	unsigned char a : 5;
+	unsigned char b : 1;
+	unsigned char c : 2;
+	unsigned char :0; // new field
+	unsigned char d : 6;
+	unsigned char e : 3;
+	// Note that C++ allows bitfields bigger than the underlying type.
+} bitfield_t;
+
 // test globals and datatypes
 extern int global;
 extern int unusedGlobal;
@@ -85,6 +96,7 @@ extern short globalArray[3];
 extern joined_t globalUnion;
 extern int globalUnionSize;
 extern option_t globalOption;
+extern bitfield_t globalBitfield;
 
 // test duplicate definitions
 int add(int a, int b);

testdata/cgo/out.txt

@@ -31,6 +31,16 @@ union local data:  5 8 1
 union s: true
 union f: +6.280000e+000
 union field: +6.280000e+000
+bitfield a: 15
+bitfield b: 1
+bitfield c: 2
+bitfield d: 47
+bitfield e: 5
+bitfield a: 7
+bitfield b: 0
+bitfield c: 3
+bitfield d: 47
+bitfield e: 5
 struct: 3 5
 n in chain: 3
 n in chain: 6