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[Qemu-block] [PATCH 2/2] trace: Forbid event format ending with newline

From: Philippe Mathieu-Daudé
Subject: [Qemu-block] [PATCH 2/2] trace: Forbid event format ending with newline character
Date: Fri, 13 Sep 2019 12:52:05 +0200

Event format ending with newlines confuse the trace reports.
Forbid them.

Add a check to refuse new format added with trailing newline:

  $ make
    GEN     hw/misc/trace.h
  Traceback (most recent call last):
    File "scripts/tracetool.py", line 152, in <module>
    File "scripts/tracetool.py", line 143, in main
      events.extend(tracetool.read_events(fh, arg))
    File "scripts/tracetool/__init__.py", line 367, in read_events
      event = Event.build(line)
    File "scripts/tracetool/__init__.py", line 281, in build
      raise ValueError("Event format can not end with a newline character")
  ValueError: Error at hw/misc/trace-events:121: Event format can not end with 
a newline character

Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
 docs/devel/tracing.txt        | 2 ++
 scripts/tracetool/__init__.py | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 76e492a489..8231bbf5d1 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -112,6 +112,8 @@ Trace events should use types as follows:
 Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
 respectively.  This ensures portability between 32- and 64-bit platforms.
+Format strings must not end with a newline character.  It is the responsibility
+of backends to adapt line ending for proper logging.
 Each event declaration will start with the event name, then its arguments,
 finally a format string for pretty-printing. For example:
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 6fca674936..57df74e67c 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -277,6 +277,9 @@ class Event(object):
         if fmt.find("%m") != -1 or fmt_trans.find("%m") != -1:
             raise ValueError("Event format '%m' is forbidden, pass the error "
                              "as an explicit trace argument")
+        if fmt.endswith("\\n\""):
+            raise ValueError("Event format must not end with a newline "
+                             "character")
         if len(fmt_trans) > 0:
             fmt = [fmt_trans, fmt]

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