cgo: support function-like macros

This is needed for code like this:

    #define __WASI_ERRNO_INVAL (UINT16_C(28))
    #define EINVAL __WASI_ERRNO_INVAL

cgo/const.go

@@ -54,8 +54,72 @@ func init() {
 }
 
 // parseConst parses the given string as a C constant.
-func parseConst(pos token.Pos, fset *token.FileSet, value string, f *cgoFile) (ast.Expr, *scanner.Error) {
+func parseConst(pos token.Pos, fset *token.FileSet, value string, params []ast.Expr, callerPos token.Pos, f *cgoFile) (ast.Expr, *scanner.Error) {
 	t := newTokenizer(pos, fset, value, f)
+
+	// If params is non-nil (could be a zero length slice), this const is
+	// actually a function-call like expression from another macro.
+	// This means we have to parse a string like "(a, b) (a+b)".
+	// We do this by parsing the parameters at the start and then treating the
+	// following like a normal constant expression.
+	if params != nil {
+		// Parse opening paren.
+		if t.curToken != token.LPAREN {
+			return nil, unexpectedToken(t, token.LPAREN)
+		}
+		t.Next()
+
+		// Parse parameters (identifiers) and closing paren.
+		var paramIdents []string
+		for i := 0; ; i++ {
+			if i == 0 && t.curToken == token.RPAREN {
+				// No parameters, break early.
+				t.Next()
+				break
+			}
+
+			// Read the parameter name.
+			if t.curToken != token.IDENT {
+				return nil, unexpectedToken(t, token.IDENT)
+			}
+			paramIdents = append(paramIdents, t.curValue)
+			t.Next()
+
+			// Read the next token: either a continuation (comma) or end of list
+			// (rparen).
+			if t.curToken == token.RPAREN {
+				// End of parameter list.
+				t.Next()
+				break
+			} else if t.curToken == token.COMMA {
+				// Comma, so there will be another parameter name.
+				t.Next()
+			} else {
+				return nil, &scanner.Error{
+					Pos: t.fset.Position(t.curPos),
+					Msg: "unexpected token " + t.curToken.String() + " inside macro parameters, expected ',' or ')'",
+				}
+			}
+		}
+
+		// Report an error if there is a mismatch in parameter length.
+		// The error is reported at the location of the closing paren from the
+		// caller location.
+		if len(params) != len(paramIdents) {
+			return nil, &scanner.Error{
+				Pos: t.fset.Position(callerPos),
+				Msg: fmt.Sprintf("unexpected number of parameters: expected %d, got %d", len(paramIdents), len(params)),
+			}
+		}
+
+		// Assign values to the parameters.
+		// These parameter names are closer in 'scope' than other identifiers so
+		// will be used first when parsing an identifier.
+		for i, name := range paramIdents {
+			t.params[name] = params[i]
+		}
+	}
+
 	expr, err := parseConstExpr(t, precedenceLowest)
 	t.Next()
 	if t.curToken != token.EOF {
@@ -96,11 +160,59 @@ func parseConstExpr(t *tokenizer, precedence int) (ast.Expr, *scanner.Error) {
 }
 
 func parseIdent(t *tokenizer) (ast.Expr, *scanner.Error) {
-	// Normally the name is something defined in the file (like another macro)
-	// which we get the declaration from using getASTDeclName.
-	// This ensures that names that are only referenced inside a macro are still
-	// getting defined.
+	// If the identifier is one of the parameters of this function-like macro,
+	// use the parameter value.
+	if val, ok := t.params[t.curValue]; ok {
+		return val, nil
+	}
+
 	if t.f != nil {
+		// Check whether this identifier is actually a macro "call" with
+		// parameters. In that case, we should parse the parameters and pass it
+		// on to a new invocation of parseConst.
+		if t.peekToken == token.LPAREN {
+			if cursor, ok := t.f.names[t.curValue]; ok && t.f.isFunctionLikeMacro(cursor) {
+				// We know the current and peek tokens (the peek one is the '('
+				// token). So skip ahead until the current token is the first
+				// unknown token.
+				t.Next()
+				t.Next()
+
+				// Parse the list of parameters until ')' (rparen) is found.
+				params := []ast.Expr{}
+				for i := 0; ; i++ {
+					if i == 0 && t.curToken == token.RPAREN {
+						break
+					}
+					x, err := parseConstExpr(t, precedenceLowest)
+					if err != nil {
+						return nil, err
+					}
+					params = append(params, x)
+					t.Next()
+					if t.curToken == token.COMMA {
+						t.Next()
+					} else if t.curToken == token.RPAREN {
+						break
+					} else {
+						return nil, &scanner.Error{
+							Pos: t.fset.Position(t.curPos),
+							Msg: "unexpected token " + t.curToken.String() + ", ',' or ')'",
+						}
+					}
+				}
+
+				// Evaluate the macro value and use it as the identifier value.
+				rparen := t.curPos
+				pos, text := t.f.getMacro(cursor)
+				return parseConst(pos, t.fset, text, params, rparen, t.f)
+			}
+		}
+
+		// Normally the name is something defined in the file (like another
+		// macro) which we get the declaration from using getASTDeclName.
+		// This ensures that names that are only referenced inside a macro are
+		// still getting defined.
 		if cursor, ok := t.f.names[t.curValue]; ok {
 			return &ast.Ident{
 				NamePos: t.curPos,
@@ -184,6 +296,7 @@ type tokenizer struct {
 	curToken, peekToken token.Token
 	curValue, peekValue string
 	buf                 string
+	params              map[string]ast.Expr
 }
 
 // newTokenizer initializes a new tokenizer, positioned at the first token in
@@ -195,6 +308,7 @@ func newTokenizer(start token.Pos, fset *token.FileSet, buf string, f *cgoFile)
 		fset:      fset,
 		buf:       buf,
 		peekToken: token.ILLEGAL,
+		params:    make(map[string]ast.Expr),
 	}
 	// Parse the first two tokens (cur and peek).
 	t.Next()
@@ -246,14 +360,16 @@ func (t *tokenizer) Next() {
 			t.peekValue = t.buf[:2]
 			t.buf = t.buf[2:]
 			return
-		case c == '(' || c == ')' || c == '+' || c == '-' || c == '*' || c == '/' || c == '%' || c == '&' || c == '|' || c == '^':
+		case c == '(' || c == ')' || c == ',' || c == '+' || c == '-' || c == '*' || c == '/' || c == '%' || c == '&' || c == '|' || c == '^':
 			// Single-character tokens.
 			// TODO: ++ (increment) and -- (decrement) operators.
 			switch c {
 			case '(':
 				t.peekToken = token.LPAREN
 			case ')':
 				t.peekToken = token.RPAREN
+			case ',':
+				t.peekToken = token.COMMA
 			case '+':
 				t.peekToken = token.ADD
 			case '-':

cgo/const_test.go

@@ -59,7 +59,7 @@ func TestParseConst(t *testing.T) {
 	} {
 		fset := token.NewFileSet()
 		startPos := fset.AddFile("", -1, 1000).Pos(0)
-		expr, err := parseConst(startPos, fset, tc.C, nil)
+		expr, err := parseConst(startPos, fset, tc.C, nil, token.NoPos, nil)
 		s := "<invalid>"
 		if err != nil {
 			if !strings.HasPrefix(tc.Go, "error: ") {

cgo/libclang.go

@@ -63,6 +63,7 @@ long long tinygo_clang_getEnumConstantDeclValue(GoCXCursor c);
 CXType tinygo_clang_getEnumDeclIntegerType(GoCXCursor c);
 unsigned tinygo_clang_Cursor_isAnonymous(GoCXCursor c);
 unsigned tinygo_clang_Cursor_isBitField(GoCXCursor c);
+unsigned tinygo_clang_Cursor_isMacroFunctionLike(GoCXCursor c);
 
 int tinygo_clang_globals_visitor(GoCXCursor c, GoCXCursor parent, CXClientData client_data);
 int tinygo_clang_struct_visitor(GoCXCursor c, GoCXCursor parent, CXClientData client_data);
@@ -370,45 +371,8 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		gen.Specs = append(gen.Specs, valueSpec)
 		return gen, nil
 	case C.CXCursor_MacroDefinition:
-		// Extract tokens from the Clang tokenizer.
-		// See: https://stackoverflow.com/a/19074846/559350
-		sourceRange := C.tinygo_clang_getCursorExtent(c)
-		tu := C.tinygo_clang_Cursor_getTranslationUnit(c)
-		var rawTokens *C.CXToken
-		var numTokens C.unsigned
-		C.clang_tokenize(tu, sourceRange, &rawTokens, &numTokens)
-		tokens := unsafe.Slice(rawTokens, numTokens)
-		// Convert this range of tokens back to source text.
-		// Ugly, but it works well enough.
-		sourceBuf := &bytes.Buffer{}
-		var startOffset int
-		for i, token := range tokens {
-			spelling := getString(C.clang_getTokenSpelling(tu, token))
-			location := C.clang_getTokenLocation(tu, token)
-			var tokenOffset C.unsigned
-			C.clang_getExpansionLocation(location, nil, nil, nil, &tokenOffset)
-			if i == 0 {
-				// The first token is the macro name itself.
-				// Skip it (after using its location).
-				startOffset = int(tokenOffset) + len(name)
-			} else {
-				// Later tokens are the macro contents.
-				for int(tokenOffset) > (startOffset + sourceBuf.Len()) {
-					// Pad the source text with whitespace (that must have been
-					// present in the original source as well).
-					sourceBuf.WriteByte(' ')
-				}
-				sourceBuf.WriteString(spelling)
-			}
-		}
-		C.clang_disposeTokens(tu, rawTokens, numTokens)
-		value := sourceBuf.String()
-		// Try to convert this #define into a Go constant expression.
-		tokenPos := token.NoPos
-		if pos != token.NoPos {
-			tokenPos = pos + token.Pos(len(name))
-		}
-		expr, scannerError := parseConst(tokenPos, f.fset, value, f)
+		tokenPos, value := f.getMacro(c)
+		expr, scannerError := parseConst(tokenPos, f.fset, value, nil, token.NoPos, f)
 		if scannerError != nil {
 			f.errors = append(f.errors, *scannerError)
 			return nil, nil
@@ -488,6 +452,62 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 	}
 }
 
+// Return whether this is a macro that's also function-like, like this:
+//
+//	#define add(a, b) (a+b)
+func (f *cgoFile) isFunctionLikeMacro(c clangCursor) bool {
+	if C.tinygo_clang_getCursorKind(c) != C.CXCursor_MacroDefinition {
+		return false
+	}
+	return C.tinygo_clang_Cursor_isMacroFunctionLike(c) != 0
+}
+
+// Get the macro value: the position in the source file and the string value of
+// the macro.
+func (f *cgoFile) getMacro(c clangCursor) (pos token.Pos, value string) {
+	// Extract tokens from the Clang tokenizer.
+	// See: https://stackoverflow.com/a/19074846/559350
+	sourceRange := C.tinygo_clang_getCursorExtent(c)
+	tu := C.tinygo_clang_Cursor_getTranslationUnit(c)
+	var rawTokens *C.CXToken
+	var numTokens C.unsigned
+	C.clang_tokenize(tu, sourceRange, &rawTokens, &numTokens)
+	tokens := unsafe.Slice(rawTokens, numTokens)
+	defer C.clang_disposeTokens(tu, rawTokens, numTokens)
+
+	// Convert this range of tokens back to source text.
+	// Ugly, but it works well enough.
+	sourceBuf := &bytes.Buffer{}
+	var startOffset int
+	for i, token := range tokens {
+		spelling := getString(C.clang_getTokenSpelling(tu, token))
+		location := C.clang_getTokenLocation(tu, token)
+		var tokenOffset C.unsigned
+		C.clang_getExpansionLocation(location, nil, nil, nil, &tokenOffset)
+		if i == 0 {
+			// The first token is the macro name itself.
+			// Skip it (after using its location).
+			startOffset = int(tokenOffset)
+		} else {
+			// Later tokens are the macro contents.
+			for int(tokenOffset) > (startOffset + sourceBuf.Len()) {
+				// Pad the source text with whitespace (that must have been
+				// present in the original source as well).
+				sourceBuf.WriteByte(' ')
+			}
+			sourceBuf.WriteString(spelling)
+		}
+	}
+	value = sourceBuf.String()
+
+	// Obtain the position of this token. This is the position of the first
+	// character in the 'value' string and is used to report errors at the
+	// correct location in the source file.
+	pos = f.getCursorPosition(c)
+
+	return
+}
+
 func getString(clangString C.CXString) (s string) {
 	rawString := C.clang_getCString(clangString)
 	s = C.GoString(rawString)

cgo/libclang_stubs.c

@@ -84,3 +84,7 @@ unsigned tinygo_clang_Cursor_isAnonymous(CXCursor c) {
 unsigned tinygo_clang_Cursor_isBitField(CXCursor c) {
 	return clang_Cursor_isBitField(c);
 }
+
+unsigned tinygo_clang_Cursor_isMacroFunctionLike(CXCursor c) {
+	return clang_Cursor_isMacroFunctionLike(c);
+}

cgo/testdata/const.go

@@ -3,13 +3,26 @@ package main
 /*
 #define foo 3
 #define bar foo
+
 #define unreferenced 4
 #define referenced unreferenced
+
+#define fnlike() 5
+#define fnlike_val fnlike()
+#define square(n) (n*n)
+#define square_val square(20)
+#define add(a, b) (a + b)
+#define add_val add(3, 5)
 */
 import "C"
 
 const (
 	Foo = C.foo
 	Bar = C.bar
+
 	Baz = C.referenced
+
+	fnlike = C.fnlike_val
+	square = C.square_val
+	add    = C.add_val
 )

cgo/testdata/const.out.go

@@ -49,3 +49,6 @@ const C.foo = 3
 const C.bar = C.foo
 const C.unreferenced = 4
 const C.referenced = C.unreferenced
+const C.fnlike_val = 5
+const C.square_val = (20 * 20)
+const C.add_val = (3 + 5)

cgo/testdata/errors.go

@@ -26,6 +26,11 @@ import "C"
 // #warning another warning
 import "C"
 
+// #define add(a, b) (a+b)
+// #define add_toomuch add(1, 2, 3)
+// #define add_toolittle add(1)
+import "C"
+
 // Make sure that errors for the following lines won't change with future
 // additions to the CGo preamble.
 //
@@ -51,4 +56,7 @@ var (
 	// constants passed by a command line parameter
 	_ = C.SOME_PARAM_CONST_invalid
 	_ = C.SOME_PARAM_CONST_valid
+
+	_ = C.add_toomuch
+	_ = C.add_toolittle
 )

cgo/testdata/errors.out.go

@@ -7,6 +7,8 @@
 //     testdata/errors.go:16:33: unexpected token ), expected end of expression
 //     testdata/errors.go:17:34: unexpected token ), expected end of expression
 //     -: unexpected token INT, expected end of expression
+//     testdata/errors.go:30:35: unexpected number of parameters: expected 2, got 3
+//     testdata/errors.go:31:31: unexpected number of parameters: expected 2, got 1
 
 // Type checking errors after CGo processing:
 //     testdata/errors.go:102: cannot use 2 << 10 (untyped int constant 2048) as C.char value in variable declaration (overflows)
@@ -17,6 +19,8 @@
 //     testdata/errors.go:114: undefined: C.SOME_CONST_b
 //     testdata/errors.go:116: undefined: C.SOME_CONST_startspace
 //     testdata/errors.go:119: undefined: C.SOME_PARAM_CONST_invalid
+//     testdata/errors.go:122: undefined: C.add_toomuch
+//     testdata/errors.go:123: undefined: C.add_toolittle
 
 package main