cgo: add support for #define constants

These are converted to Go constants where possible.

loader/cgo.go

@@ -18,6 +18,7 @@ type fileInfo struct {
 	*ast.File
 	*Package
 	filename        string
+	constants       map[string]*ast.BasicLit
 	functions       map[string]*functionInfo
 	globals         map[string]*globalInfo
 	typedefs        map[string]*typedefInfo
@@ -103,6 +104,7 @@ func (p *Package) processCgo(filename string, f *ast.File, cflags []string) []er
 		File:            f,
 		Package:         p,
 		filename:        filename,
+		constants:       map[string]*ast.BasicLit{},
 		functions:       map[string]*functionInfo{},
 		globals:         map[string]*globalInfo{},
 		typedefs:        map[string]*typedefInfo{},
@@ -163,6 +165,9 @@ func (p *Package) processCgo(filename string, f *ast.File, cflags []string) []er
 	// Declare stub function pointer values found by libclang.
 	info.addFuncPtrDecls()
 
+	// Declare globals found by libclang.
+	info.addConstDecls()
+
 	// Declare globals found by libclang.
 	info.addVarDecls()
 
@@ -287,6 +292,49 @@ func (info *fileInfo) addFuncPtrDecls() {
 	info.Decls = append(info.Decls, gen)
 }
 
+// addConstDecls declares external C constants in the Go source.
+// It adds code like the following to the AST:
+//
+//     const (
+//         C.CONST_INT = 5
+//         C.CONST_FLOAT = 5.8
+//         // ...
+//     )
+func (info *fileInfo) addConstDecls() {
+	if len(info.constants) == 0 {
+		return
+	}
+	gen := &ast.GenDecl{
+		TokPos: info.importCPos,
+		Tok:    token.CONST,
+		Lparen: info.importCPos,
+		Rparen: info.importCPos,
+	}
+	names := make([]string, 0, len(info.constants))
+	for name := range info.constants {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	for _, name := range names {
+		constVal := info.constants[name]
+		obj := &ast.Object{
+			Kind: ast.Con,
+			Name: "C." + name,
+		}
+		valueSpec := &ast.ValueSpec{
+			Names: []*ast.Ident{&ast.Ident{
+				NamePos: info.importCPos,
+				Name:    "C." + name,
+				Obj:     obj,
+			}},
+			Values: []ast.Expr{constVal},
+		}
+		obj.Decl = valueSpec
+		gen.Specs = append(gen.Specs, valueSpec)
+	}
+	info.Decls = append(info.Decls, gen)
+}
+
 // addVarDecls declares external C globals in the Go source.
 // It adds code like the following to the AST:
 //
@@ -313,7 +361,7 @@ func (info *fileInfo) addVarDecls() {
 	for _, name := range names {
 		global := info.globals[name]
 		obj := &ast.Object{
-			Kind: ast.Typ,
+			Kind: ast.Var,
 			Name: "C." + name,
 		}
 		valueSpec := &ast.ValueSpec{

loader/libclang.go

@@ -47,6 +47,7 @@ CXType tinygo_clang_getCursorResultType(GoCXCursor c);
 int tinygo_clang_Cursor_getNumArguments(GoCXCursor c);
 GoCXCursor tinygo_clang_Cursor_getArgument(GoCXCursor c, unsigned i);
 CXSourceLocation tinygo_clang_getCursorLocation(GoCXCursor c);
+CXSourceRange tinygo_clang_getCursorExtent(GoCXCursor c);
 CXTranslationUnit tinygo_clang_Cursor_getTranslationUnit(GoCXCursor c);
 
 int tinygo_clang_globals_visitor(GoCXCursor c, GoCXCursor parent, CXClientData client_data);
@@ -101,7 +102,7 @@ func (info *fileInfo) parseFragment(fragment string, cflags []string, posFilenam
 		filenameC,
 		(**C.char)(cmdargsC), C.int(len(cflags)), // command line args
 		&unsavedFile, 1, // unsaved files
-		C.CXTranslationUnit_None,
+		C.CXTranslationUnit_DetailedPreprocessingRecord,
 		&unit)
 	if errCode != 0 {
 		panic("loader: failed to parse source with libclang")
@@ -220,6 +221,86 @@ func tinygo_clang_globals_visitor(c, parent C.GoCXCursor, client_data C.CXClient
 		info.globals[name] = &globalInfo{
 			typeExpr: info.makeASTType(cursorType, pos),
 		}
+	case C.CXCursor_MacroDefinition:
+		name := getString(C.tinygo_clang_getCursorSpelling(c))
+		if _, required := info.missingSymbols[name]; !required {
+			return C.CXChildVisit_Continue
+		}
+		sourceRange := C.tinygo_clang_getCursorExtent(c)
+		start := C.clang_getRangeStart(sourceRange)
+		end := C.clang_getRangeEnd(sourceRange)
+		var file, endFile C.CXFile
+		var startOffset, endOffset C.unsigned
+		C.clang_getExpansionLocation(start, &file, nil, nil, &startOffset)
+		if file == nil {
+			panic("could not find file where macro is defined")
+		}
+		C.clang_getExpansionLocation(end, &endFile, nil, nil, &endOffset)
+		if file != endFile {
+			panic("expected start and end location of a #define to be in the same file")
+		}
+		if startOffset > endOffset {
+			panic("startOffset > endOffset")
+		}
+
+		// read file contents and extract the relevant byte range
+		tu := C.tinygo_clang_Cursor_getTranslationUnit(c)
+		var size C.size_t
+		sourcePtr := C.clang_getFileContents(tu, file, &size)
+		if endOffset >= C.uint(size) {
+			panic("endOffset lies after end of file")
+		}
+		source := string(((*[1 << 28]byte)(unsafe.Pointer(sourcePtr)))[startOffset:endOffset:endOffset])
+		if !strings.HasPrefix(source, name) {
+			panic(fmt.Sprintf("expected #define value to start with %#v, got %#v", name, source))
+		}
+		value := strings.TrimSpace(source[len(name):])
+		for len(value) != 0 && value[0] == '(' && value[len(value)-1] == ')' {
+			value = strings.TrimSpace(value[1 : len(value)-1])
+		}
+		if len(value) == 0 {
+			// Pretend it doesn't exist at all.
+			return C.CXChildVisit_Continue
+		}
+		// For information about integer literals:
+		// https://en.cppreference.com/w/cpp/language/integer_literal
+		if value[0] == '"' {
+			// string constant
+			info.constants[name] = &ast.BasicLit{pos, token.STRING, value}
+			return C.CXChildVisit_Continue
+		}
+		if value[0] == '\'' {
+			// char constant
+			info.constants[name] = &ast.BasicLit{pos, token.CHAR, value}
+			return C.CXChildVisit_Continue
+		}
+		// assume it's a number (int or float)
+		value = strings.Replace(value, "'", "", -1) // remove ' chars
+		value = strings.TrimRight(value, "lu")      // remove llu suffixes etc.
+		// find the first non-number
+		nonnum := byte(0)
+		for i := 0; i < len(value); i++ {
+			if value[i] < '0' || value[i] > '9' {
+				nonnum = value[i]
+				break
+			}
+		}
+		// determine number type based on the first non-number
+		switch nonnum {
+		case 0:
+			// no non-number found, must be an integer
+			info.constants[name] = &ast.BasicLit{pos, token.INT, value}
+		case 'x', 'X':
+			// hex integer constant
+			// TODO: may also be a floating point number per C++17.
+			info.constants[name] = &ast.BasicLit{pos, token.INT, value}
+		case '.', 'e':
+			// float constant
+			value = strings.TrimRight(value, "fFlL")
+			info.constants[name] = &ast.BasicLit{pos, token.FLOAT, value}
+		default:
+			// unknown type, ignore
+		}
 	}
 	return C.CXChildVisit_Continue
 }

loader/libclang_stubs.c

@@ -49,6 +49,10 @@ CXSourceLocation tinygo_clang_getCursorLocation(CXCursor c) {
 	return clang_getCursorLocation(c);
 }
 
+CXSourceRange tinygo_clang_getCursorExtent(CXCursor c) {
+	return clang_getCursorExtent(c);
+}
+
 CXTranslationUnit tinygo_clang_Cursor_getTranslationUnit(CXCursor c) {
 	return clang_Cursor_getTranslationUnit(c);
 }

testdata/cgo/main.go

@@ -18,6 +18,10 @@ func main() {
 	var y C.longlong = -(1 << 40)
 	println("longlong:", y)
 	println("global:", C.global)
+	println("defined ints:", C.CONST_INT, C.CONST_INT2)
+	println("defined floats:", C.CONST_FLOAT, C.CONST_FLOAT2)
+	println("defined string:", C.CONST_STRING)
+	println("defined char:", C.CONST_CHAR)
 	var ptr C.intPointer
 	var n C.int = 15
 	ptr = C.intPointer(&n)

testdata/cgo/main.h

@@ -10,6 +10,13 @@ int doCallback(int a, int b, binop_t cb);
 typedef int * intPointer;
 void store(int value, int *ptr);
 
+# define CONST_INT 5
+# define CONST_INT2 5llu
+# define CONST_FLOAT 5.8
+# define CONST_FLOAT2 5.8f
+# define CONST_CHAR 'c'
+# define CONST_STRING "defined string"
+
 // this signature should not be included by CGo
 void unusedFunction2(int x, __builtin_va_list args);
 

testdata/cgo/out.txt

@@ -4,6 +4,10 @@ myint: 3 5
 myint size: 2
 longlong: -1099511627776
 global: 3
+defined ints: 5 5
+defined floats: +5.800000e+000 +5.800000e+000
+defined string: defined string
+defined char: 99
 15: 15
 25: 25
 callback 1: 50