No fatal exceptions

[davidssmith]

Should there be an exception class that prints and error and then quits when thrown?

For example, this code seems to need to throw a fatal exception:

function check_blas()
    if blas_vendor() == :openblas
        openblas_config = openblas_get_config()
        openblas64 = ismatch(r".*USE64BITINT.*", openblas_config)
        if Base.USE_BLAS64 != openblas64
            if !openblas64
                println("ERROR: OpenBLAS was not built with 64bit integer support.")
                println("You're seeing this error because Julia was built with USE_BLAS64=1")
                println("Please rebuild Julia with USE_BLAS64=0")
            else
                println("ERROR: Julia was not built with support for OpenBLAS with 64bit integer support")
                println("You're seeing this error because Julia was built with USE_BLAS64=0")
                println("Please rebuild Julia with USE_BLAS64=1")
            end
            println("Quitting.")
            quit()
        end
    end
end

[ivarne]

Are you requesting an exception that can not be caught? That seems kind of strange.

What about?

function quit(msg::String)
    println("Quitting.")
    println(msg)
    quit()
end

[davidssmith]

It will be caught, but the default handler quits().

Is that strange?

On Thu, Nov 14, 2013 at 1:43 PM, Ivar Nesje notifications@github.comwrote:

Are you requesting an exception that can not be caught? That seems kind of
strange.

What about?

function quit(msg::String)
println("Quitting.")
println(msg)
quit()end

—
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.

[ivarne]

So user code can not catch your new exception?

If nobody catches an exception julia quits as it is now. Do you mean an exception that quits the REPL so that it does not give you a new prompt after showing the error and stacktrace?

[JeffBezanson]

We try to avoid extra features wherever possible.

[davidssmith]

I'm not proposing a new feature. I was wondering if all program exit
points should be consolidated into a FatalException handler.

On Thu, Nov 14, 2013 at 4:36 PM, Jeff Bezanson notifications@github.comwrote:

We try to avoid extra features wherever possible.

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.

[JeffBezanson]

@StefanKarpinski @ViralBShah do you think we should add a FatalException type? It doesn't seem so necessary to me.

[StefanKarpinski]

No. This is very uncommon. Almost every exception should be catchable. I do like @ivarne's idea of adding a method to quit that takes a message. That seems quite reasonable to me.

[vtjnash]

I can see an argument that this code should be allowed to cleanup, via the exception handlers, rather than just terminate:

julia> try
       quit()
       finally
       println("Bye")
       end
$ # where's my "Bye"?

But then all except blocks would need to be executed, and it's less clear if that is a good idea.

[ihnorton]

It would be nice to give the user a chance to see fatal errors before closing the REPL (I guess this is mainly an issue on Windows). Requested on list: https://groups.google.com/d/msg/julia-users/M5BTZtTUoz0/46wH40n0K0wJ

[vtjnash]

closing in favor of #15514

[cossio]

In the example of @vtjnash, I think that the exception handlers should execute only if quit() throws an exception.