From a81fd9f43408fddcf4cf2cc23eae557ed4a85a74 Mon Sep 17 00:00:00 2001
From: Luca Toniolo <10792599+grandixximo@users.noreply.github.com>
Date: Sat, 17 Oct 2026 16:02:16 +1100
Subject: [PATCH] rtapi: end an error or warning that lacks the newline

An error or a warning whose text does not end in a newline ran on into
the next message, so a repeated homing error read "j2 end of move in
home state 5j2 end of move in home state 5" (#4689). 58 error and
warning formats in the tree lack the newline, and their translations
match them.

The default message handlers of uspace now add the newline where they
print: in the main thread of rtapi_app, in the queue for messages from
its realtime threads, and in user processes. Only errors and warnings
get it. Info and debug messages, and rtapi_print(), may build a line
from several calls, as motion's debug output, the PPMC driver and
rtapi_app's cpuset report do. RTAI kernel modules are not changed.

tests/rtapi-msg-newline prints errors and a warning without a newline
from the main thread of rtapi_app and from a realtime thread, and an
info line in two parts.
---
 src/rtapi/uspace_common.h            | 10 ++++++++++
 src/rtapi/uspace_rtapi_main.cc       | 16 ++++++++++++++-
 src/rtapi/uspace_ulapi.c             | 16 ++++++++-------
 tests/rtapi-msg-newline/.gitignore   |  1 +
 tests/rtapi-msg-newline/README       |  9 +++++++++
 tests/rtapi-msg-newline/expected     |  5 +++++
 tests/rtapi-msg-newline/msgline.comp | 29 ++++++++++++++++++++++++++++
 tests/rtapi-msg-newline/msgline.hal  |  6 ++++++
 tests/rtapi-msg-newline/print.py     | 15 ++++++++++++++
 tests/rtapi-msg-newline/skip         |  4 ++++
 tests/rtapi-msg-newline/test.sh      |  6 ++++++
 11 files changed, 109 insertions(+), 8 deletions(-)
 create mode 100644 tests/rtapi-msg-newline/.gitignore
 create mode 100644 tests/rtapi-msg-newline/README
 create mode 100644 tests/rtapi-msg-newline/expected
 create mode 100644 tests/rtapi-msg-newline/msgline.comp
 create mode 100644 tests/rtapi-msg-newline/msgline.hal
 create mode 100755 tests/rtapi-msg-newline/print.py
 create mode 100755 tests/rtapi-msg-newline/skip
 create mode 100755 tests/rtapi-msg-newline/test.sh

diff --git a/src/rtapi/uspace_common.h b/src/rtapi/uspace_common.h
index 4032e7eb2fa..e6962ef5cc5 100644
--- a/src/rtapi/uspace_common.h
+++ b/src/rtapi/uspace_common.h
@@ -230,6 +230,16 @@ int rtapi_shmem_delete(int handle, int module_id)
 
 void default_rtapi_msg_handler(msg_level_t level, const char *fmt, va_list ap);
 
+/* An error or a warning is a line of its own. The default handlers end
+   one that lacks the newline, so that the next message does not run on
+   behind it. The other levels may print a line in parts. */
+static inline int rtapi_msg_needs_newline(msg_level_t level, const char *msg)
+{
+    size_t n = strlen(msg);
+    return (level == RTAPI_MSG_ERR || level == RTAPI_MSG_WARN)
+        && n > 0 && msg[n - 1] != '\n';
+}
+
 static rtapi_msg_handler_t rtapi_msg_handler = default_rtapi_msg_handler;
 
 rtapi_msg_handler_t rtapi_get_msg_handler(void) {
diff --git a/src/rtapi/uspace_rtapi_main.cc b/src/rtapi/uspace_rtapi_main.cc
index 9946f3d16d1..337bce75d90 100644
--- a/src/rtapi/uspace_rtapi_main.cc
+++ b/src/rtapi/uspace_rtapi_main.cc
@@ -1708,9 +1708,23 @@ void default_rtapi_msg_handler(msg_level_t level, const char *fmt, va_list ap) {
         message_t m;
         m.level = level;
         vsnprintf(m.msg, sizeof(m.msg), fmt, ap);
+        if (rtapi_msg_needs_newline(level, m.msg)) {
+            size_t n = strlen(m.msg);
+            if (n == sizeof(m.msg) - 1)
+                n--;	/* truncated: the newline replaces the last character */
+            m.msg[n] = '\n';
+            m.msg[n + 1] = '\0';
+        }
         rtapi_msg_queue.push(m);
     } else {
-        vfprintf(level == RTAPI_MSG_ALL ? stdout : stderr, fmt, ap);
+        FILE *f = level == RTAPI_MSG_ALL ? stdout : stderr;
+        char *msg;
+        if (vasprintf(&msg, fmt, ap) < 0)
+            return;
+        fputs(msg, f);
+        if (rtapi_msg_needs_newline(level, msg))
+            fputc('\n', f);
+        free(msg);
     }
 }
 
diff --git a/src/rtapi/uspace_ulapi.c b/src/rtapi/uspace_ulapi.c
index 0bec4b70257..65509783d3b 100644
--- a/src/rtapi/uspace_ulapi.c
+++ b/src/rtapi/uspace_ulapi.c
@@ -75,11 +75,13 @@ void rtapi_delay(long ns) {
 }
 
 void default_rtapi_msg_handler(msg_level_t level, const char *fmt, va_list ap) {
-    if(level == RTAPI_MSG_ALL) {
-	vfprintf(stdout, fmt, ap);
-        fflush(stdout);
-    } else {
-	vfprintf(stderr, fmt, ap);
-        fflush(stderr);
-    }
+    FILE *f = level == RTAPI_MSG_ALL ? stdout : stderr;
+    char *msg;
+    if (vasprintf(&msg, fmt, ap) < 0)
+        return;
+    fputs(msg, f);
+    if (rtapi_msg_needs_newline(level, msg))
+        fputc('\n', f);
+    fflush(f);
+    free(msg);
 }
diff --git a/tests/rtapi-msg-newline/.gitignore b/tests/rtapi-msg-newline/.gitignore
new file mode 100644
index 00000000000..284bd9713dd
--- /dev/null
+++ b/tests/rtapi-msg-newline/.gitignore
@@ -0,0 +1 @@
+halrun.out
diff --git a/tests/rtapi-msg-newline/README b/tests/rtapi-msg-newline/README
new file mode 100644
index 00000000000..8b724f50a9e
--- /dev/null
+++ b/tests/rtapi-msg-newline/README
@@ -0,0 +1,9 @@
+Errors and warnings whose text lacks the newline are still lines of
+their own (#4689).
+
+msgline prints two errors without a newline from its setup, which runs
+in the main thread of rtapi_app, and an error and a warning without a
+newline from its function, whose messages rtapi_app queues and prints
+from another thread. Each must be a line of its own in the output. An
+info message printed in two parts must stay one line: the levels other
+than errors and warnings may build a line from several messages.
diff --git a/tests/rtapi-msg-newline/expected b/tests/rtapi-msg-newline/expected
new file mode 100644
index 00000000000..36961ecb8e5
--- /dev/null
+++ b/tests/rtapi-msg-newline/expected
@@ -0,0 +1,5 @@
+msgline: error at load
+msgline: error at load
+msgline: error in the thread
+msgline: warning in the thread
+msgline: info in parts
diff --git a/tests/rtapi-msg-newline/msgline.comp b/tests/rtapi-msg-newline/msgline.comp
new file mode 100644
index 00000000000..536c8b50fca
--- /dev/null
+++ b/tests/rtapi-msg-newline/msgline.comp
@@ -0,0 +1,29 @@
+component msgline "Test component for tests/rtapi-msg-newline: prints messages that lack a newline";
+
+pin io bool print "set to print the messages from the realtime thread once; cleared by the function";
+
+function _;
+option extra_setup;
+option period no;
+license "GPL";
+author "Luca Toniolo";
+;;
+EXTRA_SETUP() {
+    (void)__comp_inst;
+    (void)prefix;
+    (void)extra_arg;
+    rtapi_print_msg(RTAPI_MSG_ERR, "msgline: error at load");
+    rtapi_print_msg(RTAPI_MSG_ERR, "msgline: error at load");
+    return 0;
+}
+
+FUNCTION(_) {
+    if (!print)
+        return;
+    print_set(0);
+    rtapi_print_msg(RTAPI_MSG_ERR, "msgline: error in the thread");
+    rtapi_print_msg(RTAPI_MSG_WARN, "msgline: warning in the thread");
+    /* the other levels may print a line in parts */
+    rtapi_print_msg(RTAPI_MSG_INFO, "msgline: info ");
+    rtapi_print_msg(RTAPI_MSG_INFO, "in parts\n");
+}
diff --git a/tests/rtapi-msg-newline/msgline.hal b/tests/rtapi-msg-newline/msgline.hal
new file mode 100644
index 00000000000..b985977d858
--- /dev/null
+++ b/tests/rtapi-msg-newline/msgline.hal
@@ -0,0 +1,6 @@
+loadrt threads name1=t period1=1000000
+loadrt msgline
+addf msgline.0 t
+debug 3
+start
+loadusr -w ./print.py
diff --git a/tests/rtapi-msg-newline/print.py b/tests/rtapi-msg-newline/print.py
new file mode 100755
index 00000000000..3cd8457a458
--- /dev/null
+++ b/tests/rtapi-msg-newline/print.py
@@ -0,0 +1,15 @@
+#!/usr/bin/env python3
+# Make msgline print from the realtime thread and wait until it has.
+# A wait that takes more than 10 s of wall time means the machine is
+# dying; the test then aborts.
+
+import hal
+import sys
+import time
+
+hal.set_p("msgline.0.print", "1")
+deadline = time.monotonic() + 10
+while hal.get_p("msgline.0.print"):
+    if time.monotonic() > deadline:
+        sys.exit("FAIL: the thread did not run msgline.0 in 10 s")
+    time.sleep(0.01)
diff --git a/tests/rtapi-msg-newline/skip b/tests/rtapi-msg-newline/skip
new file mode 100755
index 00000000000..14f65ebbd51
--- /dev/null
+++ b/tests/rtapi-msg-newline/skip
@@ -0,0 +1,4 @@
+#!/bin/sh
+# Builds a realtime component with halcompile, which needs the build
+# tree.  Skip when testing installed packages.
+[ -z "$SYSTEM_BUILD" ]
diff --git a/tests/rtapi-msg-newline/test.sh b/tests/rtapi-msg-newline/test.sh
new file mode 100755
index 00000000000..8c4801e3ed6
--- /dev/null
+++ b/tests/rtapi-msg-newline/test.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+set -e
+halcompile --install msgline.comp >/dev/null
+timeout -k 5 60 halrun -f msgline.hal > halrun.out 2>&1
+# the messages of msgline, each on a line of its own
+grep '^msgline:' halrun.out