[PATCH 20/73] c2xml: Guard against recursive symbols and free xmlGetProp() string

[Bart Van Assche <bvanassche@acm.org>]

Return early in examine_namespace() when sym->aux is already populated so
mutually recursive struct definitions do not trigger infinite recursion.

Guard sym->ctype.base_type->aux in examine_symbol() and release the string
allocated by xmlGetProp() with xmlFree() after xmlNewProp() copies it so
analyzing recursive struct types does not leak memory under LeakSanitizer.

Add a regression test in validation/c2xml-recursive-types.c.

Fixes: f744a1419d92 ("add c2xml program")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 c2xml.c                            | 11 +++++++++--
 validation/c2xml-recursive-types.c | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 validation/c2xml-recursive-types.c

diff --git a/c2xml.c b/c2xml.c
index 519769f72a71..f23ec1a72de4 100644
--- a/c2xml.c
+++ b/c2xml.c
@@ -190,8 +190,13 @@ static void examine_symbol(struct symbol *sym, xmlNodePtr node)
 			if (!sym->ctype.base_type->aux) {
 				examine_symbol(sym->ctype.base_type, root_node);
 			}
-			xmlNewProp(child, BAD_CAST "base-type",
-			           xmlGetProp((xmlNodePtr)sym->ctype.base_type->aux, BAD_CAST "id"));
+			if (sym->ctype.base_type->aux) {
+				xmlChar *base_id = xmlGetProp((xmlNodePtr)sym->ctype.base_type->aux, BAD_CAST "id");
+				if (base_id) {
+					xmlNewProp(child, BAD_CAST "base-type", base_id);
+					xmlFree(base_id);
+				}
+			}
 		} else {
 			newProp(child, "base-type-builtin", base);
 		}
@@ -250,6 +255,8 @@ static void examine_macro(struct symbol *sym, xmlNodePtr node)
 
 static void examine_namespace(struct symbol *sym)
 {
+	if (sym->aux)		/*already visited */
+		return;
 	if (sym->ident && sym->ident->reserved)
 		return;
 
diff --git a/validation/c2xml-recursive-types.c b/validation/c2xml-recursive-types.c
new file mode 100644
index 000000000000..210def55086b
--- /dev/null
+++ b/validation/c2xml-recursive-types.c
@@ -0,0 +1,15 @@
+struct B;
+struct A {
+	struct B *b;
+};
+struct B {
+	struct A *a;
+};
+
+/*
+ * check-name: c2xml-recursive-types
+ * check-command: c2xml $file
+ * check-output-ignore
+ * check-output-contains: <symbol type="struct".*ident="A"
+ * check-output-contains: <symbol type="struct".*ident="B"
+ */