lexer: Check that 'read' function in lex_source returns valid value.

[pspp] / src / language / lexer / lexer.c

diff --git a/src/language/lexer/lexer.c b/src/language/lexer/lexer.c
index e72a3e47bc9637d93ad3c1f764b7099686df6d3d..1caadac1de9854433d499122686d1ffa052d9704 100644 (file)
--- a/src/language/lexer/lexer.c
+++ b/src/language/lexer/lexer.c
@@ -1209,14 +1209,18 @@ lex_source_read__ (struct lex_source *src)
   do
     {
       size_t head_ofs;
+      size_t space;
       size_t n;
 
       lex_source_expand__ (src);
 
       head_ofs = src->head - src->tail;
+      space = src->allocated - head_ofs;
       n = src->reader->class->read (src->reader, &src->buffer[head_ofs],
-                                    src->allocated - head_ofs,
+                                    space,
                                     segmenter_get_prompt (&src->segmenter));
+      assert (n <= space);
+
       if (n == 0)
         {
           /* End of input.