[lttng-dev] porting LTTng to Go(lang)?

[Mathieu Desnoyers]

----- On Jun 2, 2017, at 2:27 AM, craig harmer <charmster at gmail.com> wrote: 

> hi all,

> has anyone looked at porting LTTng to [
> https://en.wikipedia.org/wiki/Go_%28programming_language%29 | Go ] (AKA [
> https://golang.org/ | Golang ] )?

Not yet ! I'm glad someone is looking into it. :) 

> Go is a language very similar to C, but it has intrinsic support for concurrency
> and better memory protection (at the expense of including garbage collection).
> its from Google and is pretty hot these days for big data and "web scale"
> distributed systems. the similarity to C is not surprising since two of the
> three authors were also involved in the development of UNIX in at AT&T in the
> 1970's: Rob Pike and Ken Thompson (Robert Griesemer is the third author).

> Go is able to link with C object files, so implementing support for tracef(3)
> should not be very difficult.

> but i want to have full support for user-defined tracepoint() events. that looks
> to be much trickier since the LTTng tracepoint() functionality relies heavily
> on (some might say abuses) the C pre-processor, and Go does not have an
> equivalent of the C pre-processor. however, i don't see an obvious reason why
> Go source files that contain tracepoints couldn't be run through the C
> pre-processor -- except that Go specific LTTng header files would be required.

> [ https://tour.golang.org/welcome/1 | here is an example of "hello, world" in Go
> ] . (note the use of "import" rather then "#include").

> i've spent more than a few hours looking at the C code generated by the C
> pre-processor trying to track down exactly why a tracepoint() definition is
> causing a compiler error, so i think i have an idea of just how hard it would
> be to development equivalent header files for Go + C pre-processor. it may be
> the case that the Go "header files", once developed, would be compiler
> specific, i.e only work with [ https://golang.org/doc/install/gccgo | gccgo ]
> (the gcc front-end for Go).

> anyway, i'm wondering if anybody has attempted this and/or what your thoughts
> would be.

In the case of C/C++ code, using the C preprocessor got the job done without requiring any additional 
dependency. Given the context you describe, perhaps it would be wise to consider introducing a dedicated 
"lttng probe description" parser. The idea here would be to parse the tracepoint probe definitions and 
translate those into native code for various languages (e.g. Golang). 

This would create a new lttng utility that would be required to to produce the language-specific files from 
those descriptions. I would allow us to port the "tracepoint" concept to many more languages easily, and 
not be so much tied to the C preprocessor anymore. 

So perhaps adding this new tool as a dependency that needs to be invoked prior to compilation might 
not be too much of an issue ? I see it as being slightly similar to the role accomplished by Flex and 
Bison: they are required to translate from source files to an intermediary language, and then the 
resulting files can be included into the distribution source packages, so only those who aim at 
changing the source descriptions need to have the translation tool installed. 

Thoughts ? 

Thanks, 

Mathieu 

> --craig

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-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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