PROTON-2248: [c] Some code doc fixes
diff --git a/c/src/core/codec.c b/c/src/core/codec.c
index 34f9d35..3719c22 100644
--- a/c/src/core/codec.c
+++ b/c/src/core/codec.c
@@ -553,8 +553,8 @@
    d: double (double)
    Z: binary (size_t, char*) - must not be NULL
    z: binary (size_t, char*) - encode as AMQP null if NULL
-   S: symbol (char*)
-   s: string (char*)
+   S: string (char*)
+   s: symbol (char*)
    D: described - next two codes are [descriptor, body]
    @: enter array. If followed by D, a described array. Following codes to matching ']' are elements.
    T: type (pn_type_t) - set array type while in array
@@ -636,8 +636,8 @@
         }
       }
       break;
-    case 'S':                   /* encode symbol or null if NULL */
-    case 's':                   /* encode string or null if NULL */
+    case 'S':                   /* encode string or null if NULL */
+    case 's':                   /* encode symbol or null if NULL */
       {
         char *start = va_arg(ap, char *);
         size_t size;