From c4867c8743e82433526b07eff3c599d05e0b7e6e Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Tue, 5 Nov 2024 08:58:40 +0100
Subject: [PATCH] cgo: define idents referenced only from macros

---
 cgo/cgo.go                |  4 ++--
 cgo/const.go              | 22 +++++++++++++++++++---
 cgo/const_test.go         |  2 +-
 cgo/libclang.go           |  2 +-
 cgo/testdata/const.go     |  3 +++
 cgo/testdata/const.out.go |  2 ++
 6 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/cgo/cgo.go b/cgo/cgo.go
index 4a5d7efed..a90b30753 100644
--- a/cgo/cgo.go
+++ b/cgo/cgo.go
@@ -1148,7 +1148,7 @@ func (f *cgoFile) getASTDeclName(name string, found clangCursor, iscall bool) st
 	if alias := cgoAliases["C."+name]; alias != "" {
 		return alias
 	}
-	node := f.getASTDeclNode(name, found, iscall)
+	node := f.getASTDeclNode(name, found)
 	if node, ok := node.(*ast.FuncDecl); ok {
 		if !iscall {
 			return node.Name.Name + "$funcaddr"
@@ -1160,7 +1160,7 @@ func (f *cgoFile) getASTDeclName(name string, found clangCursor, iscall bool) st
 
 // getASTDeclNode will declare the given C AST node (if not already defined) and
 // returns it.
-func (f *cgoFile) getASTDeclNode(name string, found clangCursor, iscall bool) ast.Node {
+func (f *cgoFile) getASTDeclNode(name string, found clangCursor) ast.Node {
 	if node, ok := f.defined[name]; ok {
 		// Declaration was found in the current file, so return it immediately.
 		return node
diff --git a/cgo/const.go b/cgo/const.go
index f4707c80a..ab088b3c8 100644
--- a/cgo/const.go
+++ b/cgo/const.go
@@ -54,8 +54,8 @@ func init() {
 }
 
 // parseConst parses the given string as a C constant.
-func parseConst(pos token.Pos, fset *token.FileSet, value string) (ast.Expr, *scanner.Error) {
-	t := newTokenizer(pos, fset, value)
+func parseConst(pos token.Pos, fset *token.FileSet, value string, f *cgoFile) (ast.Expr, *scanner.Error) {
+	t := newTokenizer(pos, fset, value, f)
 	expr, err := parseConstExpr(t, precedenceLowest)
 	t.Next()
 	if t.curToken != token.EOF {
@@ -96,6 +96,20 @@ 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 t.f != nil {
+		if cursor, ok := t.f.names[t.curValue]; ok {
+			return &ast.Ident{
+				NamePos: t.curPos,
+				Name:    t.f.getASTDeclName(t.curValue, cursor, false),
+			}, nil
+		}
+	}
+
+	// t.f is nil during testing. This is a fallback.
 	return &ast.Ident{
 		NamePos: t.curPos,
 		Name:    "C." + t.curValue,
@@ -164,6 +178,7 @@ func unexpectedToken(t *tokenizer, expected token.Token) *scanner.Error {
 
 // tokenizer reads C source code and converts it to Go tokens.
 type tokenizer struct {
+	f                   *cgoFile
 	curPos, peekPos     token.Pos
 	fset                *token.FileSet
 	curToken, peekToken token.Token
@@ -173,8 +188,9 @@ type tokenizer struct {
 
 // newTokenizer initializes a new tokenizer, positioned at the first token in
 // the string.
-func newTokenizer(start token.Pos, fset *token.FileSet, buf string) *tokenizer {
+func newTokenizer(start token.Pos, fset *token.FileSet, buf string, f *cgoFile) *tokenizer {
 	t := &tokenizer{
+		f:         f,
 		peekPos:   start,
 		fset:      fset,
 		buf:       buf,
diff --git a/cgo/const_test.go b/cgo/const_test.go
index d150e751f..c2f52c53c 100644
--- a/cgo/const_test.go
+++ b/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)
+		expr, err := parseConst(startPos, fset, tc.C, nil)
 		s := "<invalid>"
 		if err != nil {
 			if !strings.HasPrefix(tc.Go, "error: ") {
diff --git a/cgo/libclang.go b/cgo/libclang.go
index 59236bad4..c66112d53 100644
--- a/cgo/libclang.go
+++ b/cgo/libclang.go
@@ -408,7 +408,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		if pos != token.NoPos {
 			tokenPos = pos + token.Pos(len(name))
 		}
-		expr, scannerError := parseConst(tokenPos, f.fset, value)
+		expr, scannerError := parseConst(tokenPos, f.fset, value, f)
 		if scannerError != nil {
 			f.errors = append(f.errors, *scannerError)
 			return nil, nil
diff --git a/cgo/testdata/const.go b/cgo/testdata/const.go
index 43645d3ac..258942235 100644
--- a/cgo/testdata/const.go
+++ b/cgo/testdata/const.go
@@ -3,10 +3,13 @@ package main
 /*
 #define foo 3
 #define bar foo
+#define unreferenced 4
+#define referenced unreferenced
 */
 import "C"
 
 const (
 	Foo = C.foo
 	Bar = C.bar
+	Baz = C.referenced
 )
diff --git a/cgo/testdata/const.out.go b/cgo/testdata/const.out.go
index 2b48163b4..fb0bbeeba 100644
--- a/cgo/testdata/const.out.go
+++ b/cgo/testdata/const.out.go
@@ -47,3 +47,5 @@ type (
 
 const C.foo = 3
 const C.bar = C.foo
+const C.unreferenced = 4
+const C.referenced = C.unreferenced