3539

Always check if next_word() returned an empty string (if it hit eof).

Thanks Rebecca Allard for running into a crash when a .mu file ends with
'{' (without a following newline).

Open question: how to express the constraint that next_word() should
always check if its result is empty? Can *any* type system do that?!
Even the usual constraint that we must use a result isn't iron-clad: you
could save the result in a variable but then ignore it. Unless you go to
Go's extraordinary lengths of considering any dead code an error.

1 files changed, 10 insertions, 0 deletions

diff --git a/052tangle.cc b/052tangle.cc
index 50c74076..8aaecbd1 100644
--- a/052tangle.cc
+++ b/052tangle.cc
@@ -34,6 +34,11 @@ Fragments_used.clear();
 :(before "End Command Handlers")
 else if (command == "before") {
   string label = next_word(in);
+  if (label.empty()) {
+    assert(!has_data(in));
+    raise << "incomplete 'before' block at end of file\n" << end();
+    return result;
+  }
   recipe tmp;
   slurp_body(in, tmp);
   if (is_waypoint(label))
@@ -44,6 +49,11 @@ else if (command == "before") {
 }
 else if (command == "after") {
   string label = next_word(in);
+  if (label.empty()) {
+    assert(!has_data(in));
+    raise << "incomplete 'after' block at end of file\n" << end();
+    return result;
+  }
   recipe tmp;
   slurp_body(in, tmp);
   if (is_waypoint(label))