luaa: add stack dumping debug function

Signed-off-by: Julien Danjou <julien@danjou.info>

luaa.h

@@ -23,9 +23,12 @@
 #define AWESOME_LUA_H
 
 #include <ev.h>
+
 #include <lua.h>
 #include <lauxlib.h>
 
+#include <stdio.h>
+
 #include "draw.h"
 #include "common/util.h"
 
@@ -92,6 +95,40 @@ typedef int luaA_ref;
             luaL_error(L, "invalid screen number: %d", screen + 1); \
     } while(0)
 
+/** Dump the Lua stack. Useful for debugging.
+ * \param L The Lua VM state.
+ */
+static inline void
+luaA_dumpstack(lua_State *L)
+{
+    fprintf(stderr, "-------- Lua stack dump ---------\n");
+    for(int i = lua_gettop(L); i; i--)
+    {
+        int t = lua_type(L, i);
+        switch (t)
+        {
+          case LUA_TSTRING:
+            fprintf(stderr, "%d: string: `%s'\n", i, lua_tostring(L, i));
+            break;
+          case LUA_TBOOLEAN:
+            fprintf(stderr, "%d: bool:   %s\n", i, lua_toboolean(L, i) ? "true" : "false");
+            break;
+          case LUA_TNUMBER:
+            fprintf(stderr, "%d: number: %g\n", i, lua_tonumber(L, i));
+            break;
+          case LUA_TNIL:
+            fprintf(stderr, "%d: nil\n", i);
+            break;
+          default:
+            fprintf(stderr, "%d: %s\t#%d\t%p\n", i, lua_typename(L, t),
+                    (int) lua_objlen(L, i),
+                    lua_topointer(L, i));
+            break;
+        }
+    }
+    fprintf(stderr, "------- Lua stack dump end ------\n");
+}
+
 /** Check that an object is not a NULL reference.
  * \param L The Lua state.
  * \param ud The index of the object in the stack.