Calling CLOSE-FILE twice

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This topic contains 2 replies, has 3 voices, and was last updated by  Leon Wagner 1 year, 11 months ago.

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    Rene Hartmann

    I wonder if it is safe to call CLOSE-FILE on a file id that has been closed before.

    SwiftForth returns -197 if CLOSE-FILE is called twice. Can one rely on this behaviour?

    I checked with GForth, and it crashes when CLOSE-FILE is called twice. I guess there a fileid is a pointer to a block of memory that is freed when CLOSE-FILE is called.



    My original program:

    : FILE-CLOSE \ ( — )
    fileid @ CLOSE-FILE diskfault ! ;

    My trial programs:

    : FILE-CLOSE \ ( — )
    fileid @ CLOSE-FILE diskfault ! fileid @ CLOSE-FILE DROP ;

    : FILE-CLOSE \ ( — )
    fileid @ CLOSE-FILE diskfault ! 0 CLOSE-FILE DROP ;

    Both trial programs worked properly without crashing the computer. My program that calls this opens and closes hundreds of files in a fraction of a second, not just one file, so I feel my test is pretty good.

    Best wishes — Allen Anway


    Leon Wagner

    The Forth Standard definition of CLOSE-FILE says this:

    ( fileid — ior )
    Close the file identified by fileid. ior is the implementation-defined I/O result code.

    The list of standard ior and throw code values are defined in the Forth-2012 standard here. It specifies -62 as the ior for a fail in CLOSE-FILE. We’ll be updating our throw codes to match the new standard in an upcoming release. I would not expect CLOSE-FILE to crash or do anything other than return an error ior if the fileid can’t be closed (for whatever reason).

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