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

[John Snow]

On 9/13/19 6:52 AM, Philippe Mathieu-Daudé wrote:
> 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>
>       main(sys.argv)
>     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 "

It's barely worth mentioning, but you can use r"\n" for cases like this,
if it makes it easier to read.