Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-29 Thread Philippe Proulx via lttng-dev 
- Original Message -
> From: "Mathieu Desnoyers" 
> To: "Philippe Proulx" 
> Cc: "gbastien+lttng" , "Matthew Khouzam" 
> , "Jeremie
> Galarneau" , "lttng-dev" , 
> "diamon-discuss"
> 
> Sent: Wednesday, 29 April, 2020 08:08:04
> Subject: Re: [RFC PATCH CTF 1/3] Clarify that unlisted enum values are 
> implementation-defined

> - On Apr 28, 2020, at 2:51 PM, Mathieu Desnoyers
> mathieu.desnoy...@efficios.com wrote:
> 
>> - On Apr 28, 2020, at 2:40 PM, Philippe Proulx ppro...@efficios.com 
>> wrote:
>> 
>>> - Original Message -
 From: "Mathieu Desnoyers" 
 To: "gbastien+lttng" , "Matthew Khouzam"
 ,
 diamon-disc...@linuxfoundation.org, ppro...@efficios.com, "Jeremie 
 Galarneau"
 
 Cc: "lttng-dev" , "Mathieu Desnoyers"
 
 Sent: Thursday, 23 April, 2020 16:52:24
 Subject: [RFC PATCH CTF 1/3] Clarify that unlisted enum values are
 implementation-defined
>>> 
 From: Geneviève Bastien 
 
 Signed-off-by: Geneviève Bastien 
 Signed-off-by: Mathieu Desnoyers 
 ---
 common-trace-format-specification.md | 3 +++
 1 file changed, 3 insertions(+)
 
 diff --git a/common-trace-format-specification.md
 b/common-trace-format-specification.md
 index fd49e59..f5fea51 100644
 --- a/common-trace-format-specification.md
 +++ b/common-trace-format-specification.md
 @@ -464,6 +464,9 @@ enum {
 }
 ~~~
 
 +The mappings in the enumeration type do not have to be exhaustive.
 +Unlisted values are implementation defined.
 +
>>> 
>>> Why not just:
>>> 
>>>An enumeration field can have an integral value which its type does not
>>>map to a string.
>>> 
>>> ?
>> 
>> Good point, I will use that wording.
> 
> Geneviève pointed out on IRC that the sentence above is weird. Would the
> following convey the right meaning ?
> 
> "An enumeration field can have an integral value for which the associated
> enumeration
> type does not map to a string."

Sure.

Phil

> 
> Thanks,
> 
> Mathieu
> 
>> 
>> Thanks,
>> 
>> Mathieu
>> 
>>> 
>>> Phil
>>> 
 ### 4.2 Compound types
 
 Compound are aggregation of type declarations. Compound types include
 --
>>> > 2.11.0
>> 
>> --
>> Mathieu Desnoyers
>> EfficiOS Inc.
>> http://www.efficios.com
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
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Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-29 Thread Mathieu Desnoyers via lttng-dev 
- On Apr 28, 2020, at 2:51 PM, Mathieu Desnoyers 
mathieu.desnoy...@efficios.com wrote:

> - On Apr 28, 2020, at 2:40 PM, Philippe Proulx ppro...@efficios.com wrote:
> 
>> - Original Message -
>>> From: "Mathieu Desnoyers" 
>>> To: "gbastien+lttng" , "Matthew Khouzam"
>>> ,
>>> diamon-disc...@linuxfoundation.org, ppro...@efficios.com, "Jeremie 
>>> Galarneau"
>>> 
>>> Cc: "lttng-dev" , "Mathieu Desnoyers"
>>> 
>>> Sent: Thursday, 23 April, 2020 16:52:24
>>> Subject: [RFC PATCH CTF 1/3] Clarify that unlisted enum values are
>>> implementation-defined
>> 
>>> From: Geneviève Bastien 
>>> 
>>> Signed-off-by: Geneviève Bastien 
>>> Signed-off-by: Mathieu Desnoyers 
>>> ---
>>> common-trace-format-specification.md | 3 +++
>>> 1 file changed, 3 insertions(+)
>>> 
>>> diff --git a/common-trace-format-specification.md
>>> b/common-trace-format-specification.md
>>> index fd49e59..f5fea51 100644
>>> --- a/common-trace-format-specification.md
>>> +++ b/common-trace-format-specification.md
>>> @@ -464,6 +464,9 @@ enum {
>>> }
>>> ~~~
>>> 
>>> +The mappings in the enumeration type do not have to be exhaustive.
>>> +Unlisted values are implementation defined.
>>> +
>> 
>> Why not just:
>> 
>>An enumeration field can have an integral value which its type does not
>>map to a string.
>> 
>> ?
> 
> Good point, I will use that wording.

Geneviève pointed out on IRC that the sentence above is weird. Would the
following convey the right meaning ?

"An enumeration field can have an integral value for which the associated 
enumeration
type does not map to a string."

Thanks,

Mathieu

> 
> Thanks,
> 
> Mathieu
> 
>> 
>> Phil
>> 
>>> ### 4.2 Compound types
>>> 
>>> Compound are aggregation of type declarations. Compound types include
>>> --
>> > 2.11.0
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-28 Thread Mathieu Desnoyers via lttng-dev 
- On Apr 28, 2020, at 2:40 PM, Philippe Proulx ppro...@efficios.com wrote:

> - Original Message -
>> From: "Mathieu Desnoyers" 
>> To: "gbastien+lttng" , "Matthew Khouzam"
>> ,
>> diamon-disc...@linuxfoundation.org, ppro...@efficios.com, "Jeremie Galarneau"
>> 
>> Cc: "lttng-dev" , "Mathieu Desnoyers"
>> 
>> Sent: Thursday, 23 April, 2020 16:52:24
>> Subject: [RFC PATCH CTF 1/3] Clarify that unlisted enum values are
>> implementation-defined
> 
>> From: Geneviève Bastien 
>> 
>> Signed-off-by: Geneviève Bastien 
>> Signed-off-by: Mathieu Desnoyers 
>> ---
>> common-trace-format-specification.md | 3 +++
>> 1 file changed, 3 insertions(+)
>> 
>> diff --git a/common-trace-format-specification.md
>> b/common-trace-format-specification.md
>> index fd49e59..f5fea51 100644
>> --- a/common-trace-format-specification.md
>> +++ b/common-trace-format-specification.md
>> @@ -464,6 +464,9 @@ enum {
>> }
>> ~~~
>> 
>> +The mappings in the enumeration type do not have to be exhaustive.
>> +Unlisted values are implementation defined.
>> +
> 
> Why not just:
> 
>An enumeration field can have an integral value which its type does not
>map to a string.
> 
> ?

Good point, I will use that wording.

Thanks,

Mathieu

> 
> Phil
> 
>> ### 4.2 Compound types
>> 
>> Compound are aggregation of type declarations. Compound types include
>> --
> > 2.11.0

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-28 Thread Philippe Proulx via lttng-dev 
- Original Message -
> From: "Mathieu Desnoyers" 
> To: "gbastien+lttng" , "Matthew Khouzam" 
> ,
> diamon-disc...@linuxfoundation.org, ppro...@efficios.com, "Jeremie Galarneau" 
> 
> Cc: "lttng-dev" , "Mathieu Desnoyers" 
> 
> Sent: Thursday, 23 April, 2020 16:52:24
> Subject: [RFC PATCH CTF 1/3] Clarify that unlisted enum values are 
> implementation-defined

> From: Geneviève Bastien 
> 
> Signed-off-by: Geneviève Bastien 
> Signed-off-by: Mathieu Desnoyers 
> ---
> common-trace-format-specification.md | 3 +++
> 1 file changed, 3 insertions(+)
> 
> diff --git a/common-trace-format-specification.md
> b/common-trace-format-specification.md
> index fd49e59..f5fea51 100644
> --- a/common-trace-format-specification.md
> +++ b/common-trace-format-specification.md
> @@ -464,6 +464,9 @@ enum {
> }
> ~~~
> 
> +The mappings in the enumeration type do not have to be exhaustive.
> +Unlisted values are implementation defined.
> +

Why not just:

An enumeration field can have an integral value which its type does not
map to a string.

?

Phil

> ### 4.2 Compound types
> 
> Compound are aggregation of type declarations. Compound types include
> --
> 2.11.0
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Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-24 Thread Mathieu Desnoyers via lttng-dev 
- On Apr 23, 2020, at 6:51 PM, Jeremie Galarneau 
jeremie.galarn...@efficios.com wrote:

> On Thu, 23 Apr 2020 at 16:52, Mathieu Desnoyers
>  wrote:
>>
>> From: Geneviève Bastien 
>>
>> Signed-off-by: Geneviève Bastien 
>> Signed-off-by: Mathieu Desnoyers 
>> ---
>>  common-trace-format-specification.md | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/common-trace-format-specification.md
>> b/common-trace-format-specification.md
>> index fd49e59..f5fea51 100644
>> --- a/common-trace-format-specification.md
>> +++ b/common-trace-format-specification.md
>> @@ -464,6 +464,9 @@ enum {
>>  }
>>  ~~~
>>
>> +The mappings in the enumeration type do not have to be exhaustive.
>> +Unlisted values are implementation defined.
>> +
> 
> This is too vague to be useful knowing that the main rationale for this
> change is to allow enums to express some type of bitfield of flags
> in the tracer and readers [1].
> 
> What is the meaning of an unmapped value? This section should at
> least describe the correct interpretation of unmapped values as flags
> and when it is appropriate to do so.

Considering that this is a patchlevel update to CTF, I would not expect
that we introduce new features in the specification. Only clarifications
to parts of the specification that were unclear.

Specifying a new behavior related to unmapped values would fall IMO into the
realm of "new feature", and would belong to a CTF 1.9 or CTF 2.0. As we
all know, there is a CTF 2.0 in the making, but it does not solve the
immediate problem of LTTng 2.12 which produces those unmapped enum values
within traces identified as CTF 1.8.

Moreover, to add to the problem, Babeltrace 2 has a strict match on CTF 1.8
in the CTF source plugin, and won't accept a CTF 1.9 trace (unlike Babeltrace 1
which would emit a warning about possibly unsupported features, but would accept
a 1.9 CTF trace nevertheless).

So this is why I am proposing this minimal clarification to the CTF 1.8
specification: that unmapped enum values are implementation defined (rather
than saying nothing about them). Considering that tracers can generate this
kind of trace data anyway, it's really a consideration that should have been
explicitly expressed in the specification from the start and was an
involuntary omission.

So perhaps we need to state something more than just "implementation defined",
but it's unclear what without ending up adding features into a patchlevel
update.

Thanks,

Mathieu


> Thanks,
> Jérémie
> 
> [1] https://review.lttng.org/c/babeltrace/+/3045
> 
>>  ### 4.2 Compound types
>>
>>  Compound are aggregation of type declarations. Compound types include
>> --
>> 2.11.0
>>
> 
> 
> --
> Jérémie Galarneau
> EfficiOS Inc.
> http://www.efficios.com

-- 
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EfficiOS Inc.
http://www.efficios.com
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Re: [lttng-dev] [RFC PATCH CTF 1/3] Clarify that unlisted enum values are implementation-defined

2020-04-23 Thread Jérémie Galarneau via lttng-dev 
On Thu, 23 Apr 2020 at 16:52, Mathieu Desnoyers
 wrote:
>
> From: Geneviève Bastien 
>
> Signed-off-by: Geneviève Bastien 
> Signed-off-by: Mathieu Desnoyers 
> ---
>  common-trace-format-specification.md | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/common-trace-format-specification.md 
> b/common-trace-format-specification.md
> index fd49e59..f5fea51 100644
> --- a/common-trace-format-specification.md
> +++ b/common-trace-format-specification.md
> @@ -464,6 +464,9 @@ enum {
>  }
>  ~~~
>
> +The mappings in the enumeration type do not have to be exhaustive.
> +Unlisted values are implementation defined.
> +

This is too vague to be useful knowing that the main rationale for this
change is to allow enums to express some type of bitfield of flags
in the tracer and readers [1].

What is the meaning of an unmapped value? This section should at
least describe the correct interpretation of unmapped values as flags
and when it is appropriate to do so.

Thanks,
Jérémie

[1] https://review.lttng.org/c/babeltrace/+/3045

>  ### 4.2 Compound types
>
>  Compound are aggregation of type declarations. Compound types include
> --
> 2.11.0
>


-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
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