The results of a session with valgrind.

I'm surprised that this highly experimental code, built with chewing gum and chicken wire,
had so little problems, and most of those where leaks.  The majority of problems reported
are from external libraries.

1 files changed, 12 insertions, 10 deletions

diff --git a/src/libraries/Runnr.c b/src/libraries/Runnr.c
index b775e19..72bc523 100644
--- a/src/libraries/Runnr.c
+++ b/src/libraries/Runnr.c
@@ -151,6 +151,9 @@ static char *_push_name(lua_State *L, char *q, int *idx)  // Stack usage [-0, +1
   return q;
 }
 
+/* It's the callers job to stash things safely before returning from the Lua to C function call.
+ * Coz things like strings might go away after the stack is freed.
+ */
 int pull_lua(lua_State *L, int i, char *params, ...)         // Stack usage -
                                                              // if i is a table
                                                              //   [-n, +n, e]
@@ -210,16 +213,15 @@ int pull_lua(lua_State *L, int i, char *params, ...)         // Stack usage -
                   if (lua_isstring(L, j))                                // Stack usage [-0, +0, -]
                     {
                        char **v = va_arg(vl, char **);
-                       size_t len;
-                       char *temp = (char *) lua_tolstring(L, j, &len);  // Stack usage [-0, +0, m]
-
-                       len++;  // Cater for the null at the end.
-                       *v = malloc(len);
-                       if (*v)
-                         {
-                            memcpy(*v, temp, len);
-                            n++;
-                         }
+
+                       // We could strdup the string, but that causes leaks.
+                       // The problem is that the caller doesn't know if we allocated or not,
+                       // since the incoming pointer could already be pointing to a default value.
+                       // Lua says the string is valid until it's popped off the stack,
+                       // and this is used only in calls to C functions from Lua.
+                       // So just document that it's the callers job to stash it safely if needed after returning.
+                       *v = (char *) lua_tostring(L, j);
+                       n++;
                     }
                   break;
                }