When reading files out of the scratch disk, don't die with an error

exit code if there's a bad signature, because that's a guest error not
a host error.  (If we do exit with an error code, it fouls up the
grading process.)  Instead, just make sure that the host file(s) we
were supposed to retrieve is unlinked.

diff --git a/src/utils/pintos b/src/utils/pintos
index b803c949068eef8108bfd3dfbd02e32f30070be5..a4b0feb5ccd52a43a5160871e3ee59cc0260b94e 100755 (executable)
--- a/src/utils/pintos
+++ b/src/utils/pintos
@@ -268,7 +268,15 @@ sub finish_scratch_disk {
     }
 
     # Read each file.
-    get_scratch_file (defined ($_->[1]) ? $_->[1] : $_->[0]) foreach @gets;
+    # If reading fails, delete that file and all subsequent files.
+    my ($ok) = 1;
+    foreach my $get (@gets) {
+       my ($name) = defined ($get->[1]) ? $get->[1] : $get->[0];
+       $ok &&= get_scratch_file ($name);
+       if (!$ok) {
+           die "$name: unlink: $!\n" if !unlink ($name) && !$!{ENOENT};
+       }
+    }
 }
 
 # put_scratch_file($file).
@@ -303,6 +311,7 @@ sub put_scratch_file {
 # get_scratch_file($file).
 #
 # Copies from the scratch disk to $file.
+# Returns 1 if successful, 0 on failure.
 sub get_scratch_file {
     my ($get_file_name) = @_;
     my ($disk_handle, $disk_file_name) = open_disk ($disks{SCRATCH});
@@ -313,8 +322,9 @@ sub get_scratch_file {
     # the file size.
     my ($metadata) = read_fully ($disk_handle, $disk_file_name, 512);
     my ($signature, $size) = unpack ("a4 V", $metadata);
-    die "bad signature reading scratch disk--did Pintos run correctly?\n"
-      if $signature ne "GET\0";
+    (print STDERR "bad signature on scratch disk--did Pintos run fail?\n"),
+      return 0
+       if $signature ne "GET\0";
 
     # Copy file data.
     my ($get_handle);
@@ -327,6 +337,8 @@ sub get_scratch_file {
     # Skip forward in disk up to beginning of next sector.
     read_fully ($disk_handle, $disk_file_name, 512 - $size % 512)
       if $size % 512;
+
+    return 1;
 }
 \f
 # Prepares the arguments to pass to the Pintos kernel,