[libvirt] Redesigning Libvirt: Adopting use of a safe language

[Martin Kletzander]

On Tue, Nov 28, 2017 at 10:25:37AM +0000, Daniel P. Berrange wrote:
>On Tue, Nov 28, 2017 at 10:22:21AM +0000, Daniel P. Berrange wrote:
>> On Tue, Nov 28, 2017 at 08:43:54AM +0100, Martin Kletzander wrote:
>> > Just a quick note on what I've found out after I dedicated half day to go
>> > through the tour of go and some other tutorials.  The learning curve of Go is
>> > even less steep than I though (for some unknown reason) it is.  So that's in
>> > favor of Go.  However I haven't found out how is it possible to avoid some
>> > SIGSEGVs or aborts since Go doesn't have many recoverable errors.  And in some
>> > cases they are not easy to spot immediately.  Or making sure struct fields are
>> > initialized.  Since libvirt strives to go for recoverable errors, I see this as
>> > a downside.
>>
>> Either I'm mis-understanding what you mean, or you missed the 'recover'
>> function. In normal operation, error reporting is dealt with by having
>> functions return a value that implements the 'error' interface. Functions
>> can have multiple return values, so typically you would return a pair of
>> values, the first being the data, the second being the error indicator.
>> You check & deal with those errors with normal control flow statements.
>>
>> For cases where the code triggered a runtime panic() (eg dereference a
>> Nil pointer), ordinarily that will terminate the program. At point in
>> the callstack, however, can catch that panic using the recover() method
>> which avoids termination, and resumes normal execution. Typically in an
>> RPC server, the RPC dispatch method would use recover() so that if any
>> RPC method execution  panic()s the server carries on running normally,
>> only that one method is terminated.
>>
>> The only thing that you can't catch is when you call into C code and
>> that crashes. The C code can obviously arbitrarily corrupt memory, so
>> there's no safe way to recover that. Only the Go can be recover()d from.
>
>Opps, meant to include this link
>
>  https://blog.golang.org/defer-panic-and-recover
>

Oh, I didn't know about this, that's cool.  I totally missed the recover()
function.  Thanks for the info and the link!  I'm starting to feel like I know
Go now :D

>Regards,
>Daniel
>-- 
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