[eqn] Handle border cases of `delim on' and `delim off'.

* src/preproc/eqn/lex.cpp (do_delim): Handle multiple sequences of
`delim on' gracefully (ditto for `delim off').

1 files changed, 8 insertions, 4 deletions

diff --git a/src/preproc/eqn/lex.cpp b/src/preproc/eqn/lex.cpp
index 899ecaeb..ed8930f5 100644
--- a/src/preproc/eqn/lex.cpp
+++ b/src/preproc/eqn/lex.cpp
@@ -1071,13 +1071,17 @@ void do_delim()
   else {
     if (c == 'o' && d == 'f' && peek_char() == 'f') {
       (void)get_char();
-      start_delim_saved = start_delim;
-      end_delim_saved = end_delim;
+      if (start_delim)
+        start_delim_saved = start_delim;
+      if (end_delim)
+        end_delim_saved = end_delim;
       start_delim = end_delim = '\0';
     }
     else if (c == 'o' && d == 'n' && !compatible_flag) {
-      start_delim = start_delim_saved;
-      end_delim = end_delim_saved;
+      if (start_delim_saved)
+        start_delim = start_delim_saved;
+      if (end_delim_saved)
+        end_delim = end_delim_saved;
     }
     else {
       start_delim = c;