[DTrace-devel] [PATCH v2] enum: support declarations with a trailing comma

[Alan Maguire]

When doing python tracing, it was recently observed that #include'ing
a file with enum declarations with trailing commas fails; this is
due to the D grammar being strict about the last enumerator value
not having a trailing comma.  So

enum foo {
	BAR,
	BAZ
};

is permitted, but

enum foo {
	BAR,
	BAZ,
};

is not.  The latter pattern is used quite frequently in #include
files, especially where conditional compilation of some enum
values is done.

Relax this constraint and add a test to validate that D compilation
succeeds with the trailing comma in an enum declaration.

Signed-off-by: Alan Maguire <alan.maguire at oracle.com>

Changes since v1:

- fixed commit description, updated test to cover enum, anon enum,
  typedef enum variations for both trailing comma case and without it
---
 libdtrace/dt_grammar.y                     |  3 +-
 test/unittest/enum/tst.EnumTrailingComma.d | 66 ++++++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 test/unittest/enum/tst.EnumTrailingComma.d

diff --git a/libdtrace/dt_grammar.y b/libdtrace/dt_grammar.y
index 677cd869..7984b85d 100644
--- a/libdtrace/dt_grammar.y
+++ b/libdtrace/dt_grammar.y
@@ -702,7 +702,8 @@ enum_definition:
 
 enumerator_list:
 		enumerator
-	|	enumerator_list DT_TOK_COMMA enumerator
+	|	enumerator DT_TOK_COMMA enumerator_list
+	|	enumerator DT_TOK_COMMA
 	;
 
 enumerator:	DT_TOK_IDENT { dt_decl_enumerator($1, NULL); }
diff --git a/test/unittest/enum/tst.EnumTrailingComma.d b/test/unittest/enum/tst.EnumTrailingComma.d
new file mode 100644
index 00000000..fcf200e9
--- /dev/null
+++ b/test/unittest/enum/tst.EnumTrailingComma.d
@@ -0,0 +1,66 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/*
+ * ASSERTION:
+ * Enumerations should support declaration with a trailing comma for
+ * the last enumeration value as well as non-comma case.
+ *
+ * SECTION: Type and Constant Definitions/Enumerations
+ *
+ * NOTES:
+ *
+ */
+
+#pragma D option quiet
+
+enum colors {
+	RED = 1,
+	GREEN = 2,
+	BLUE = 3, 
+};
+
+enum weather {
+	CLOUDY,
+	SUNNY
+};
+
+enum {
+	CIRCLE,
+	SQUARE,
+	TRIANGLE,
+};
+
+enum {
+	HEXAGON,
+	OCTAGON
+};
+
+typedef enum {
+	RIGHT,
+	LEFT,
+} horizontal_t;
+
+typedef enum {
+	UP,
+	DOWN
+} vertical_t;
+
+typedef enum motor_transport {
+	CAR,
+	MOTORBIKE,
+} motor_transport_t;
+
+typedef enum nonmotor_transport {
+	BIKE,
+	SKATEBOARD
+} nonmotor_trasport_t;
+
+BEGIN
+{
+	exit(0);
+}
-- 
2.43.5