--- a/js/src/gdb/lib-for-tests/catcher.py
+++ b/js/src/gdb/lib-for-tests/catcher.py
@@ -1,19 +1,22 @@
 # Apparently, there's simply no way to ask GDB to exit with a non-zero
-# status when the script run with the --python option fails. Thus, if we
-# have --python run prolog.py directly, syntax errors there will lead GDB
-# to exit with no indication anything went wrong.
+# 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:
-    execfile(sys.argv.pop(0))
+    # 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)

--- a/js/src/gdb/lib-for-tests/prolog.py
+++ b/js/src/gdb/lib-for-tests/prolog.py
@@ -1,13 +1,17 @@
 import gdb
+import os
 import re
 import sys
 import traceback
 
+# testlibdir is set on the GDB command line, via --eval-command python testlibdir=...
+sys.path[0:0] = [testlibdir]
+
 # Run the C++ fragment named |fragment|, stopping on entry to |function|
 # ('breakpoint', by default) and then select the calling frame.
 def run_fragment(fragment, function='breakpoint'):
     # Arrange to stop at a reasonable place in the test program.
     bp = gdb.Breakpoint(function);
     try:
         gdb.execute("run %s" % (fragment,))
         # Check that we did indeed stop by hitting the breakpoint we set.
@@ -53,17 +57,19 @@ gdb.execute('set confirm off', False)
 
 # Some print settings that make testing easier.
 gdb.execute('set print static-members off')
 gdb.execute('set print address off')
 gdb.execute('set print pretty off')
 gdb.execute('set width 0')
 
 try:
-    execfile(sys.argv[0])
+    # testscript is set on the GDB command line, via:
+    # --eval-command python testscript=...
+    execfile(testscript)
 except AssertionError as err:
     sys.stderr.write('\nAssertion traceback:\n')
     (t, v, tb) = sys.exc_info()
     traceback.print_tb(tb)
     sys.stderr.write('\nTest assertion failed:\n')
     sys.stderr.write(str(err))
     sys.exit(1)
 

--- a/js/src/gdb/run-tests.py
+++ b/js/src/gdb/run-tests.py
@@ -154,20 +154,19 @@ class Test(TaskPool.Task):
     def cmd(self):
         testlibdir = os.path.normpath(os.path.join(OPTIONS.testdir, '..', 'lib-for-tests'))
         return [OPTIONS.gdb_executable,
                 '-nw',          # Don't create a window (unnecessary?)
                 '-nx',          # Don't read .gdbinit.
                 '--ex', 'add-auto-load-safe-path %s' % (OPTIONS.builddir,),
                 '--ex', 'set env LD_LIBRARY_PATH %s' % (OPTIONS.libdir,),
                 '--ex', 'file %s' % (os.path.join(OPTIONS.builddir, 'gdb-tests'),),
-                '--eval-command', 'python sys.path[0:0] = [%r]' % testlibdir,
-                '--python', os.path.join(testlibdir, 'catcher.py'),
-                            os.path.join(testlibdir, 'prolog.py'),
-                self.test_path]
+                '--eval-command', 'python testlibdir=%r' % (testlibdir,),
+                '--eval-command', 'python testscript=%r' % (self.test_path,),
+                '--eval-command', 'python execfile(%r)' % os.path.join(testlibdir, 'catcher.py')]
 
     def start(self, pipe, deadline):
         super(Test, self).start(pipe, deadline)
         if OPTIONS.show_cmd:
             self.summary.interleave_output(lambda: self.show_cmd(sys.stdout))
 
     def onStdout(self, text):
         self.stdout += text