[Mesa-dev] [PATCH] glcpp: error on multiple #else directives

[Erik Faye-Lund]

The preprocessor currently eats multiple #else directives
int the same #if(def) ... #endif block. While I haven't been able
to find anything that explicitly disallows it, it's nonsensical
and should probably not be allowed.

Add checks to reject the code.
---

I'm not entirely sure why parser->skip_stack can be NULL after
_glcpp_parser_skip_stack_change_if, but apparently it is for at
least one test.

I'm also not entirely sure if this should be an error or a warning.
Thoughts?

 src/glsl/glcpp/glcpp-parse.y                      | 13 ++++++++++++-
 src/glsl/glcpp/glcpp.h                            |  1 +
 src/glsl/glcpp/tests/118-multiple-else.c          |  6 ++++++
 src/glsl/glcpp/tests/118-multiple-else.c.expected |  8 ++++++++
 4 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 src/glsl/glcpp/tests/118-multiple-else.c
 create mode 100644 src/glsl/glcpp/tests/118-multiple-else.c.expected

diff --git a/src/glsl/glcpp/glcpp-parse.y b/src/glsl/glcpp/glcpp-parse.y
index 6eaa5f9..885c64d 100644
--- a/src/glsl/glcpp/glcpp-parse.y
+++ b/src/glsl/glcpp/glcpp-parse.y
@@ -332,7 +332,17 @@ control_line:
 		}
 	}
 |	HASH_ELSE {
-		_glcpp_parser_skip_stack_change_if (parser, & @1, "else", 1);
+		if (parser->skip_stack &&
+		    parser->skip_stack->has_else)
+		{
+			glcpp_error(& @1, parser, "multiple #else");
+		}
+		else
+		{
+			_glcpp_parser_skip_stack_change_if (parser, & @1, "else", 1);
+			if (parser->skip_stack)
+				parser->skip_stack->has_else = true;
+		}
 	} NEWLINE
 |	HASH_ENDIF {
 		_glcpp_parser_skip_stack_pop (parser, & @1);
@@ -2012,6 +2022,7 @@ _glcpp_parser_skip_stack_push_if (glcpp_parser_t *parser, YYLTYPE *loc,
 		node->type = SKIP_TO_ENDIF;
 	}
 
+	node->has_else = false;
 	node->next = parser->skip_stack;
 	parser->skip_stack = node;
 }
diff --git a/src/glsl/glcpp/glcpp.h b/src/glsl/glcpp/glcpp.h
index 8aaa551..ccae96c 100644
--- a/src/glsl/glcpp/glcpp.h
+++ b/src/glsl/glcpp/glcpp.h
@@ -153,6 +153,7 @@ typedef enum skip_type {
 
 typedef struct skip_node {
 	skip_type_t type;
+	bool has_else;
 	YYLTYPE loc; /* location of the initial #if/#elif/... */
 	struct skip_node *next;
 } skip_node_t;
diff --git a/src/glsl/glcpp/tests/118-multiple-else.c b/src/glsl/glcpp/tests/118-multiple-else.c
new file mode 100644
index 0000000..62ad49c
--- /dev/null
+++ b/src/glsl/glcpp/tests/118-multiple-else.c
@@ -0,0 +1,6 @@
+#if 0
+#else
+int foo;
+#else
+int bar;
+#endif
diff --git a/src/glsl/glcpp/tests/118-multiple-else.c.expected b/src/glsl/glcpp/tests/118-multiple-else.c.expected
new file mode 100644
index 0000000..eaec481
--- /dev/null
+++ b/src/glsl/glcpp/tests/118-multiple-else.c.expected
@@ -0,0 +1,8 @@
+0:4(1): preprocessor error: multiple #else
+
+
+int foo;
+
+int bar;
+
+
-- 
1.8.3.1