feat: extend alarmdefault and argecho

user/consolereader2.c

@@ -0,0 +1,30 @@
+#include "ulib.h"
+
+/* See consolereader1.c's comment -- an entirely independent process reading
+   the same fd 0, spawned separately by kmain.c, sharing nothing with
+   consolereader1 but the fact that both happen to be alive when
+   consoleInjectorThread's single synthetic keystroke fires. If fan-out
+   ever regressed back to one shared buffer, whichever of the two processes
+   the scheduler happened to run first would steal the only queued byte and
+   the other would hang forever -- the boot gate's timeout would catch that
+   as a missing needle rather than a hang, since only this process is
+   missing, not the whole machine. */
+
+int main(void)
+{
+    print("consolereader2: start, pid=");
+    printDec(userGetpid());
+    print(", blocking on fd 0\n");
+
+    char c = 0;
+    long got = userRead(0, &c, 1);
+    if (got != 1) {
+        print("consolereader2: FAIL read\n");
+        return 1;
+    }
+
+    print("consolereader2: got byte '");
+    userWrite(1, &c, 1);
+    print("' -> console-fanout-2-ok\n");
+    return 0;
+}