diff -r 000000000000 -r 6474c204b198 js/src/gdb/lib-for-tests/catcher.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/gdb/lib-for-tests/catcher.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,22 @@
+# Apparently, there's simply no way to ask GDB to exit with a non-zero
+# status when the script run with the --eval-command option fails. Thus, if
+# we have --eval-command run prolog.py directly, syntax errors there will
+# lead GDB to exit with no indication anything went wrong.
+#
+# To avert that, we use this very small launcher script to run prolog.py
+# and catch errors.
+#
+# Remember, errors in this file will cause spurious passes, so keep this as
+# simple as possible!
+
+import os
+import sys
+import traceback
+try:
+    # testlibdir is set on the GDB command line, via:
+    # --eval-command python testlibdir=...
+    execfile(os.path.join(testlibdir, 'prolog.py'))
+except Exception as err:
+    sys.stderr.write('Error running GDB prologue:\n')
+    traceback.print_exc()
+    sys.exit(1)