util: string: Introduce macro for automatic string lists

Similar to VIR_AUTOPTR, VIR_AUTOSTRINGLIST defines a list of strings
which will be freed if the pointer is leaving scope.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/libvirt_private.syms

@@ -2958,6 +2958,7 @@ virStringHasControlChars;
 virStringIsEmpty;
 virStringIsPrintable;
 virStringListAdd;
+virStringListAutoFree;
 virStringListFree;
 virStringListFreeCount;
 virStringListGetFirstWithPrefix;

src/util/virstring.c

@@ -318,6 +318,16 @@ void virStringListFree(char **strings)
 }
 
 
+void virStringListAutoFree(char ***strings)
+{
+    if (!*strings)
+        return;
+
+    virStringListFree(*strings);
+    *strings = NULL;
+}
+
+
 /**
  * virStringListFreeCount:
  * @strings: array of strings to free

src/util/virstring.h

@@ -53,6 +53,7 @@ int virStringListCopy(char ***dst,
                       const char **src);
 
 void virStringListFree(char **strings);
+void virStringListAutoFree(char ***strings);
 void virStringListFreeCount(char **strings,
                             size_t count);
 
@@ -307,6 +308,15 @@ int virStringParsePort(const char *str,
                        unsigned int *port)
     ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
 
+/**
+ * VIR_AUTOSTRINGLIST:
+ *
+ * Declares a NULL-terminated list of strings which will be automatically freed
+ * when the pointer goes out of scope.
+ */
+# define VIR_AUTOSTRINGLIST \
+        __attribute__((cleanup(virStringListAutoFree))) char **
+
 VIR_DEFINE_AUTOPTR_FUNC(virString, virStringListFree);
 
 #endif /* LIBVIRT_VIRSTRING_H */