----- Original Message ----- > From: "Stefan Seefeld" <[email protected]> > To: "Mathieu Desnoyers" <[email protected]> > Cc: [email protected] > Sent: Monday, February 3, 2014 10:41:14 AM > Subject: Re: [lttng-dev] [Patch LTTng-ust 6/7] Add the macros to generate the > data structures for CTF named > enumerations > > On 02/03/2014 10:28 AM, Mathieu Desnoyers wrote: > > > Hi Stefan, > > > > Let's try to make sure I understand your intent here. Let's say we have > > an event with a "weight" field (uint32_t). You would like to have > > a multiplicative factor (e.g. *1000 for "kg") as a second field, that would > > be entirely known from the metadata (pretty much a C literal in the > > metadata, > > so it does not have to be repeated for each event). > > Right. The analogy with a C literal isn't entirely sufficient, as there > is a range of situations where in fact "constant" doesn't map to > compile-time constant in C/C++. Thus...
Can you provide a concrete example of what you envision ? What would this look like an an "extended" CTF metadata ? Thanks, Mathieu > > > There are various ways to do this I imagine: e.g.: > > > > * Using the typing system > > > [...] > > ...the typing system can't quite capture values that are immutable > within a running session, but not quite constant in the sense that they > can be captured in a type system. > > So perhaps another way to look at it is like a static class member, for > which storage isn't part of each instance of the class, but rather > somewhere that's associated with all instances of the class... > > > But I don't see anything there that requires adding any top-level construct > > to the CTF metadata. > > ...and that "somewhere" would naturally be the metadata section of the > traces. > > > Hence, I am tempted to keep the name "global type declaration" > > for the part of metadata located in the "global" section (opposed to within > > a > > trace, env, stream, and event scope). Anyway, all we can declare there are > > types, > > so it makes sense to use this name. If we ever add something to the CTF > > spec in the > > future that is global but is not a type, then we'll have to extend the > > interfaces > > and implementations (which should be expected if we extend the CTF spec). > > Right. I wasn't arguing so much against the use of "global type > declaration" for the case of named enums, but merely wanted to point out > that the mechanism could be extended to cover non-type-related metadata. > > Thanks, > Stefan > > > -- > Stefan Seefeld > CodeSourcery / Mentor Graphics > http://www.mentor.com/embedded-software/ > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
