Fix a memory management bug in list concatination noted is issue #30.

Author: BrentSeidel

src/bbs-lisp-evaluate-symb.adb

@@ -264,10 +264,10 @@ package body BBS.lisp.evaluate.symb is
          -- Concatinate lists
          --
          declare
-            cons_head : cons_index := NIL_CONS;
-            dest_cons : cons_index := NIL_CONS;
-            temp_cons : cons_index := NIL_CONS;
-            src_cons : cons_index := NIL_CONS;
+            cons_head : cons_index := NIL_CONS;  --  Head of list being built
+            dest_cons : cons_index := NIL_CONS;  --  Current element in list being built
+            temp_cons : cons_index := NIL_CONS;  --  New cons cell to add to list
+            src_cons : cons_index := NIL_CONS;   --  Source list to copy from
          begin
             if s1 = NIL_CONS then
                error("concatenate", "Cannot concatenate a single element.");
@@ -279,31 +279,40 @@ package body BBS.lisp.evaluate.symb is
                if t2.kind = V_ERROR then
                   error("concatenate", "Error reported evaluating additional parameters.");
                   e := t2;
+                  BBS.lisp.conses.deref(cons_head);
                   return;
                end if;
                src_cons := getList(t2);
                if src_cons = NIL_CONS then
                   error("concatenate", "Parameter does not evaluate to a list");
                   BBS.lisp.memory.deref(t2);
+                  BBS.lisp.conses.deref(cons_head);
                   e := make_error(ERR_WRONGTYPE);
                   return;
                end if;
                loop
                   if not BBS.lisp.conses.alloc(temp_cons) then
                      error("concatenate", "Unable to allocate cons cell.");
                      BBS.lisp.conses.deref(cons_head);
+                     BBS.lisp.conses.deref(src_cons);
                      e := make_error(ERR_ALLOCCONS);
                      return;
                   end if;
                   if cons_head = NIL_CONS then
                      cons_head := temp_cons;
                      dest_cons := temp_cons;
                   else
+                     --
+                     --  Point end of list to new cons cell and update end of list.
+                     --
                      BBS.lisp.conses.set_cdr(dest_cons, (kind => V_LIST, l => temp_cons));
                      dest_cons := temp_cons;
                   end if;
+                  --
+                  --  Copy the value from the source list and move to the next
+                  --  element in the source.
+                  --
                   BBS.lisp.conses.set_car(dest_cons, BBS.lisp.conses.get_car(src_cons));
-                  BBS.lisp.memory.ref(BBS.lisp.conses.get_car(dest_cons));
                   src_cons := getList(BBS.lisp.conses.get_cdr(src_cons));
                   if src_cons = NIL_CONS then
                      exit;

src/bbs-lisp-info.ads

@@ -4,9 +4,9 @@ package BBS.lisp.info is
    --  the test coverage script.  It should not be edited by hand.
    --
    name           : constant String  := "Tiny Lisp";
-   timestamp      : constant String  := "Fri Aug  6 11:19:32 MST 2021";
-   build_date     : constant String  := "2021-Aug-06 (master)";
+   timestamp      : constant String  := "Sun Aug  8 11:50:18 MST 2021";
+   build_date     : constant String  := "2021-Aug-08 (master)";
    version_string : constant String  := "V00.03+";
-   version_date   : constant Integer := 20210806;  -- yyyymmdd
+   version_date   : constant Integer := 20210808;  -- yyyymmdd
    version_number : constant Integer := 2;
 end;