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



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

Regards,
Daniel
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