Improve doxygen documentation.

include/ucore/dstr.h

@@ -8,7 +8,7 @@
 extern "C" {
 #endif
 
-/** A managed C-string, using dynalically allocated memory for the string.
+/** A managed C-string, using dynamically allocated memory for the string.
  *
  * The .str member might not always be nul terminated,
  * Normally, use uc_dstr_str() to retreive the managed string
@@ -52,8 +52,11 @@ int uc_dstr_init_str_sz(struct DStr *str, const char *init, size_t len);
  */
 void uc_dstr_destroy(struct DStr *str);
 
-/** Copy a DStr
- *
+/** Copy a DStr.
+ *  The @dest string should not be an initialized string since it will be 
+ *  initialized by uc_dstr_copy, and would cause a memory leak if it's already
+ *  initialized.
+ * 
  * @param dest destination string to copy to, must not contain an existing string
  * @param src DStr to copy
  *