cgo: implement char type

This type is a bit more difficult because it can be signed or unsigned
depending on the target platform.

loader/cgo.go

@@ -66,6 +66,7 @@ var cgoAliases = map[string]string{
 // somehow from C. This is done by adding some typedefs to get the size of each
 // type.
 const cgoTypes = `
+typedef char                _Cgo_char;
 typedef signed char         _Cgo_schar;
 typedef unsigned char       _Cgo_uchar;
 typedef short               _Cgo_short;

loader/libclang.go

@@ -203,7 +203,19 @@ func tinygo_clang_globals_visitor(c, parent C.GoCXCursor, client_data C.CXClient
 			expr := expr.(*ast.Ident)
 			typeSize := C.clang_Type_getSizeOf(underlyingType)
 			switch expr.Name {
-			// TODO: plain char (may be signed or unsigned)
+			case "C.char":
+				if typeSize != 1 {
+					// This happens for some very special purpose architectures
+					// (DSPs etc.) that are not currently targeted.
+					// https://www.embecosm.com/2017/04/18/non-8-bit-char-support-in-clang-and-llvm/
+					panic("unknown char width")
+				}
+				switch underlyingType.kind {
+				case C.CXType_Char_S:
+					expr.Name = "int8"
+				case C.CXType_Char_U:
+					expr.Name = "uint8"
+				}
 			case "C.schar", "C.short", "C.int", "C.long", "C.longlong":
 				switch typeSize {
 				case 1:
@@ -253,6 +265,8 @@ func getString(clangString C.CXString) (s string) {
 func (info *fileInfo) makeASTType(typ C.CXType) ast.Expr {
 	var typeName string
 	switch typ.kind {
+	case C.CXType_Char_S, C.CXType_Char_U:
+		typeName = "C.char"
 	case C.CXType_SChar:
 		typeName = "C.schar"
 	case C.CXType_UChar:

testdata/cgo/main.c

@@ -8,6 +8,7 @@ double globalDouble = 3.2;
 _Complex float globalComplexFloat = 4.1+3.3i;
 _Complex double globalComplexDouble = 4.2+3.4i;
 _Complex double globalComplexLongDouble = 4.3+3.5i;
+char globalChar = 100;
 collection_t globalStruct = {256, -123456, 3.14, 88};
 int globalStructSize = sizeof(globalStruct);
 short globalArray[3] = {5, 6, 7};

testdata/cgo/main.go

@@ -40,6 +40,7 @@ func main() {
 	println("complex float:", C.globalComplexFloat)
 	println("complex double:", C.globalComplexDouble)
 	println("complex long double:", C.globalComplexLongDouble)
+	println("char match:", C.globalChar == 100)
 
 	// complex types
 	println("struct:", C.int(unsafe.Sizeof(C.globalStruct)) == C.globalStructSize, C.globalStruct.s, C.globalStruct.l, C.globalStruct.f)

testdata/cgo/main.h

@@ -36,6 +36,7 @@ extern double globalDouble;
 extern _Complex float globalComplexFloat;
 extern _Complex double globalComplexDouble;
 extern _Complex double globalComplexLongDouble;
+extern char globalChar;
 extern collection_t globalStruct;
 extern int globalStructSize;
 extern short globalArray[3];

testdata/cgo/out.txt

@@ -14,6 +14,7 @@ double: +3.200000e+000
 complex float: (+4.100000e+000+3.300000e+000i)
 complex double: (+4.200000e+000+3.400000e+000i)
 complex long double: (+4.300000e+000+3.500000e+000i)
+char match: true
 struct: true 256 -123456 +3.140000e+000
 array: 5 6 7
 union: true