datasheet: Add a few assertions.

These made the problem a bit more obvious while tracking down bug #30689.

diff --git a/src/data/datasheet.c b/src/data/datasheet.c
index 4abc526f0cb2a720cb8e3023eb7d732effdb5da4..de59e73fe842f4fa94009d24b626cc9157464306 100644 (file)
--- a/src/data/datasheet.c
+++ b/src/data/datasheet.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2007, 2009 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -360,6 +360,8 @@ datasheet_insert_column (struct datasheet *ds,
 {
   struct column *col;
 
+  assert (before <= ds->n_columns);
+
   ds->columns = xnrealloc (ds->columns,
                            ds->n_columns + 1, sizeof *ds->columns);
   insert_element (ds->columns, ds->n_columns, sizeof *ds->columns, before);
@@ -382,6 +384,8 @@ datasheet_insert_column (struct datasheet *ds,
 void
 datasheet_delete_columns (struct datasheet *ds, size_t start, size_t n)
 {
+  assert (start + n <= ds->n_columns);
+
   if (n > 0)
     {
       size_t i;
@@ -411,6 +415,9 @@ datasheet_move_columns (struct datasheet *ds,
                         size_t old_start, size_t new_start,
                         size_t n)
 {
+  assert (old_start + n <= ds->n_columns);
+  assert (new_start + n <= ds->n_columns);
+
   move_range (ds->columns, ds->n_columns, sizeof *ds->columns,
               old_start, new_start, n);