A missing file is an error, not a core dump

Naming a pad file that is not there printed the error and then said the
machine had STARTED. MACHINE_OK is nought and the code returned nought, so
the front end ran a machine whose clock had never been set up and divided
by it: a typo in a path came out as a floating point exception and a core
dump.

The trap is two functions in one file with opposite conventions -
machineStart returns MACHINE_OK for worked, machineRestart thirty lines up
returns 1 for worked - and this copied the nearer one. Both of the returns
I added last week had it.

Checked now for all three files the replay suite is about, because the
same mistake fits all of them, and re-broken to be sure: the check comes
back exit 136, which is a signal 8, which is the crash.

Found by somebody typing a path that was not there, which is the fourth
thing this week that no test would have reached.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Source/Emulator/machine.c

@@ -225,6 +225,15 @@ uint8_t machineStart(Machine *m, const EmulatorOptions *options, const char *pro
     }
     // ---- The pads, from files ----
     //
+    // MACHINE_ERROR and not nought. Nought is MACHINE_OK here, so returning it after printing
+    // an error said the machine had started - and the front end then ran a machine whose
+    // clock had never been set up and divided by it. A missing file came out as a floating
+    // point exception and a core dump.
+    //
+    // The trap is that machineRestart, thirty lines up, returns 1 for worked and 0 for did
+    // not. Two functions in one file with opposite conventions, and this copied the nearer
+    // one.
+    //
     // Opened here beside the keyboard because they are the same kind of thing: a recording
     // standing in for a person, so that what a person would exercise is reachable from a
     // suite. They are never closed, for the same reason the keyboard is not - the machine
@@ -233,7 +242,7 @@ uint8_t machineStart(Machine *m, const EmulatorOptions *options, const char *pro
         FILE *pad = fopen(options->pads[n], "rb");
         if (pad == NULL) {
             fprintf(stderr, "Error: Couldn't open pad file: %s\n", options->pads[n]);
-            return 0;
+            return MACHINE_ERROR;
         }
         padFromFile(n, pad);
     }
@@ -242,7 +251,7 @@ uint8_t machineStart(Machine *m, const EmulatorOptions *options, const char *pro
         FILE *pad = fopen(options->padRecord, "wb");
         if (pad == NULL) {
             fprintf(stderr, "Error: Couldn't write pad file: %s\n", options->padRecord);
-            return 0;
+            return MACHINE_ERROR;
         }
         padRecordTo(pad);
     }

Tests/replay.sh

@@ -114,6 +114,30 @@ print('yes' if set(data) <= {0} else 'no')
     && result ok "and nothing held is written as nothing" "no buttons nobody pressed" \
     || result no "and nothing held is written as nothing" "the recording holds something"
 
+# ---- A file that is not there is an error, not a crash ----
+#
+# Naming a pad file that does not exist used to print the error and then say the machine had
+# STARTED: MACHINE_OK is nought, and the code returned nought. The front end then ran a
+# machine whose clock had never been set up and divided by it, so a typo in a path came out as
+# a floating point exception and a core dump.
+#
+# The trap was two functions in one file with opposite conventions - machineRestart returns 1
+# for worked - and the wrong neighbour being copied. Checked here for all three files this
+# suite is about, because the same mistake fits all of them.
+for missing in "--pad" "--keyboard" "--record-pad"; do
+    case "$missing" in
+        --record-pad) where="/nowhere/at/all.pad" ;;
+        *)            where="$BUILD/there-is-no-such-file" ;;
+    esac
+    "$EMU" $missing "$where" "$BUILD/padTest.bin" > "$BUILD/missing.out" 2>&1
+    status=$?
+    if [ "$status" = "1" ] && grep -q "Error:" "$BUILD/missing.out"; then
+        result ok "$missing with no file stops cleanly" "an error and a status, not a signal"
+    else
+        result no "$missing with no file stops cleanly" "exit $status"
+    fi
+done
+
 echo
 if [ "$FAIL" -eq 0 ]; then
     echo "All $PASS replay checks passed."