[Vm-dev] FilePlugin>>primitiveFileStdioHandles fails incorrectly?

[Eliot Miranda]

Hi Alistair,

On Thu, Aug 9, 2018 at 1:37 AM, Alistair Grant <akgrant0710 at gmail.com>
wrote:

>
> Hi Eliot,
>
> On Wed, 8 Aug 2018 at 21:31, Eliot Miranda <eliot.miranda at gmail.com>
> wrote:
> >
> >
> > Hi Alistair,
> >
> > On Sun, Aug 5, 2018 at 1:02 PM, Alistair Grant <akgrant0710 at gmail.com>
> wrote:
> >>
> >>
> >> Hi Everyone,
> >>
> >> FilePlugin>>primitiveFileStdioHandles is responsible for opening stdio
> >> in the VM.  The basic behaviour is to call sqFileStdioHandlesInto()
> >> which does the actual work and returns a mask indicating which streams
> >> were successfully opened (stdin, stdout, stderr).
> >>
> >> However primitiveFileStdioHandles regards a mask of 0, i.e. no files
> >> available, as a primitive failure:
> >>
> >>
> >> sHFAfn ~= 0 ifTrue:
> >>     [(self cCode: ' ((sqInt (*)(void))sHFAfn)()' inSmalltalk: [true])
> ifFalse:
> >>         [^interpreterProxy primitiveFailFor: PrimErrUnsupported]].
> >> self cCode: '' inSmalltalk: [fileRecords := Array new: 3].
> >> validMask := self sqFileStdioHandlesInto: fileRecords.
> >> validMask = 0 ifTrue:
> >>     [^interpreterProxy primitiveFailFor: PrimErrUnsupported].
> >>
> >>
> >> This doesn't cause a problem in squeak since all primitive errors are
> >> handled by simply assuming that the stdio files can't be opened and
> >> ignoring any other errors.
> >>
> >> Pharo currently raises an unhandled exception.
> >>
> >> On Windows not having stdio available is a normal condition, so
> >> I think the correct behaviour is for the primitive to succeed, but
> >> return an array of 3 nils, i.e. successfully determined that none of the
> >> stdio files are available (this is effectively what happens in the
> >> Squeak image anyway).
> >>
> >> It would then mean that a primitive failure can be treated as something
> >> going wrong, rather than the normal (on Windows) situation of no stdio
> >> files being available.
> >>
> >> The other (minor) benefit is that at the moment there are two situations
> >> in which the primitive fails with PrimErrUnsupported: sHFAfn ~= 0 and
> >> validMask = 0.  This change would make it easier to interpret the
> >> failure.
> >>
> >> Any objections?
> >
> >
> > No, but I think the right thing to do is to fail if
> sqFileStdioHandlesInto answers a value less than zero.  That would;d still
> allow the subsystem to communicate some serious error, while allowing the
> system also to report that no streams are available (e.g. when not attached
> to a console).
>
> Wouldn't it  be better for sqFileStdioHandlesInto to flag the
> primitive as failing itself as it could then provide a reason, e.g.
> primitiveFailFor or primitiveFailForOSError? (the platform support
> file is already doing this in other support routines).
>
>
> > BTW, is there any image level source code available for accessing the
> FileAttributesPlugin's primitives?  This is lazy of me, but if there is
> could you email me a pointer to the code or the code itself asap?  TIA
> >
> > P.S> I'm specifically looking for code to implement testing directory
> writability in Squeak.
>
> OK, just a warning in advance: The code (VM and image) works fine on
> Linux and Windows.  I didn't know about the Mac file encoding quirks
> until recently, so need to change the plugin to work properly on Mac
> OS.  But I haven't got the VM to compile on my Mac virtualbox machine,
> so the changes are still local to my PC.  This won't affect you unless
> you've got non-ascii characters in your file names.  I should have
> fixed this by now, but the problems compiling on Mac have frustrated
> me, and I've had very little time (personal reasons).
>

I develop on the Mac so feel free to email me a change set and tests (e.g.
just doit in a workspace) and IO can test for you.


>
> The main repository for the image side file attributes code is at:
> https://github.com/akgrant43/pharo/tree/21368-Integrate-
> FileAttributesPlugin.
>

OK, I'll see if I can grab this wen I have time. Today is taken :-)


>
> If you're not comfortable with git I think figuring out the changes
> will be difficult.  I've got a .cs from a slightly earlier revision
> which I can email you - probably directly, it's 93Kb.
>
> I'll try and put together a change set which just includes enough code
> to get file attributes.
>

I've got myself going.  I have the R_OK, W_OK, E_OK accessors in place so
don't need source code.  I do suggest however that primitiveFileAttribute
would be nicer to use if it took its arguments in reverse order.  i.e.

    attribute: attributeNumber forPath: path

is less clumsy than

    attributeForPath: path numbered: attributeNumber


> Any other questions, of course please let me know.
>
> Cheers,
> Alistair
>


_,,,^..^,,,_
best, Eliot
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