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 <philmd@redhat.com>
---
 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]
-- 
2.20.1

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 <philmd@redhat.com>
> ---
>  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.

On 9/13/19 10:01 PM, John Snow wrote:
> 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 <philmd@redhat.com>
>> ---
>>  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.

TIL Python r"" :)

This would be r"\n\"", right? We need to match the trailing '"'.
Same length, not sure which string is easier to review =)

On 9/13/19 5:00 PM, Philippe Mathieu-Daudé wrote:
> On 9/13/19 10:01 PM, John Snow wrote:
>> 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 <philmd@redhat.com>
>>> ---
>>>  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.
> 
> TIL Python r"" :)
> 
> This would be r"\n\"", right? We need to match the trailing '"'.
> Same length, not sure which string is easier to review =)
> 

Ah, wow, I did misread this. It's confusing!

In this case, you can use r'\n"' to get the job done.

(My r-b stands, anyway.)

--js