test(parser): pin the trailing comment of a TEXT and GLOBL header

Assisted-by: GLM 5.3 Flash

parser/flags.go

@@ -62,8 +62,10 @@ var flagOrder = []struct {
 	{"ABIWRAPPER", 4096},
 }
 
-// flagsRun prepares one flags operand for evaluation: the comments are
-// dropped, they are layout the expression never sees.
+// flagsRun strips the comments from one flags operand.  A comment on a
+// directive line is always its trailing text (a comment mid-line is the
+// statement boundary the statement reader makes of it), so what the
+// operand split hands over carries it at the tail at most.
 func flagsRun(g []token.Token) []token.Token {
 	out := make([]token.Token, 0, len(g))
 	for _, t := range g {

parser/flags_test.go

@@ -226,3 +226,16 @@ func TestGloblFlagsOperand(t *testing.T) {
 		t.Errorf("failed operand must carry no value")
 	}
 }
+
+// TestTrailingCommentInHeader covers the comment a directive line carries:
+// it is the line's trailing text, the operand split hands the frame over
+// before it, and the header parses exactly as it would without it.
+func TestTrailingCommentInHeader(t *testing.T) {
+	txt := parseTextHeader(t, "TEXT \u00b7f(SB), NOSPLIT, $0 /* d */")
+	if !slices.Equal(txt.Flags, []string{"NOSPLIT"}) {
+		t.Errorf("flags = %v, want [NOSPLIT]", txt.Flags)
+	}
+	if txt.FlagVal != 4 || txt.Frame == nil || !txt.Frame.Imm.HasVal || txt.Frame.Imm.Val != 0 {
+		t.Errorf("val = %d frame = %+v, want 4 and $0", txt.FlagVal, txt.Frame)
+	}
+}

parser/parser.go

@@ -255,13 +255,15 @@ func (p *state) parseText(line []token.Token) {
 	// two, the first is the flags expression and the last the frame; with
 	// three or more, the toolchain's own complaint.  One operand is the
 	// frame alone, whatever it starts with, so a malformed frame takes the
-	// frame diagnostic and never reads as flags.
+	// frame diagnostic and never reads as flags.  A trailing comment ends
+	// the operands and never joins them; a comment mid-header is the
+	// statement boundary the statement reader has always made of it.
 	rest = skipComma(rest)
 	ops := splitOperands(rest)
 	var frame []token.Token
 	switch {
 	case len(ops) >= 2:
-		text.Flags, text.FlagVal = p.evalFlags(flagsRun(ops[0]), false, "TEXT")
+		text.Flags, text.FlagVal = p.evalFlags(ops[0], false, "TEXT")
 		frame = ops[1]
 		if len(ops) > 2 {
 			p.errorf(line[0].Pos, "expect two or three operands for TEXT")
@@ -355,7 +357,7 @@ func (p *state) parseGlobl(line []token.Token) *ast.Globl {
 	ops := splitOperands(rest)
 	switch {
 	case len(ops) >= 2:
-		g.Flags, g.FlagVal = p.evalFlags(flagsRun(ops[0]), true, "GLOBL")
+		g.Flags, g.FlagVal = p.evalFlags(ops[0], true, "GLOBL")
 		g.Size = parseOperand(ops[1], false)
 	case len(ops) == 1:
 		g.Size = parseOperand(ops[0], false)