feat: introduce streq and printErr

user/pollwriter.c

@@ -0,0 +1,51 @@
+#include "ulib.h"
+
+/*
+ * Only ever spawned by polltest.c, with the shared pipe's handle number as
+ * argv[1] (decToString'd -- see polltest.c, mirrors fifomaster.c's own
+ * handle-passing convention). Sleeps well past when polltest.c will
+ * already be parked inside its own userPoll(..., -1) call, so the write
+ * below has to actually wake it back up (schedWakeChannel(schedPollChannel()),
+ * pipeWrite in pipe.c) instead of polltest simply finding the pipe already
+ * readable -- proof the block was real, not a lucky race, the same shape
+ * fifowriter.c already proves for a plain blocking read().
+ */
+
+/* Comfortably longer than polltest.c's own phase-2 bounded-timeout poll
+   (pollTimeoutMs, polltest.c) -- pollwriter is spawned immediately, at the
+   very start of polltest.c (mirroring fifomaster.c's own immediate double-
+   spawn), so by the time polltest reaches its phase-3 blocking multi-fd
+   poll, phase 2's own wait has already used up part of this delay; the
+   margin here guarantees phase 3 still genuinely has to block and be woken
+   by the write below, not race a write that already happened. */
+#define pollWriterDelayMs 500
+
+static const char* payload = "poll payload";
+
+int main(int argc, char** argv)
+{
+    if (argc != 2) {
+        print("pollwriter: FAIL expected one argv (pipe handle)\n");
+        return 1;
+    }
+
+    long handle = parseDec(argv[1]);
+    long fd = userPipeAttach(handle, 1);
+    if (fd < 0) {
+        print("pollwriter: FAIL attach\n");
+        return 1;
+    }
+
+    print("pollwriter: attached, sleeping before write\n");
+    userSleep(pollWriterDelayMs);
+
+    long written = userWrite((int)fd, payload, stringLength(payload));
+    if (written != (long)stringLength(payload)) {
+        print("pollwriter: FAIL short/failed write\n");
+        return 1;
+    }
+    print("pollwriter: wrote payload\n");
+
+    userClose((int)fd);
+    return 0;
+}