stdio functions

Beginning with the MiNTLib 0.54.99 the MiNTLib uses a new binary interface for stdio functions. This is actually incompatible with the old interface because the definition of FILE in differs significantly from former versions.

Despite of this binary incompatibility you will seldom have to recompile old libraries or object files to get them to work with the new MiNTLib. Clean code never makes assumptions about the internal representation of FILE and since only pointers to FILE are used, things will still work.

One exception from the above are the standard streams stdin, stdout and stderr, which were implemented as macros in :

    extern FILE _iob[];
    #define stdin &_iob[0];
    #define stdout &_iob[1];
    #define stderr &_iob[2];

Since the size of a FILE has changed from previous versions to current versions, all stdio on standard streams should not work. However, the MiNTLib still defines the symbol "_iob" and glues these old streams to the new stdin, stdout and stderr (see stdio/glue.c). Old libraries/object files will not notice any difference on the standard streams and will keep on working.

Unfortunately there were also two problematic macros in which dragged assumptions about the internal representation of a FILE into all code. The glue code can stil grok with compiled code that used the macros getc() and fileno(), as long as the arguments are one of the standard streams (stdin, stdout, stderr). For all other streams this will not work any longer, and such files have to be recompiled.

Other problematic macros that couldn't be emulated were

    ferror (FILE* stream)
    feof (FILE* stream)
    clearerr (FILE* stream)

Code that uses these macros also has to be recompiled against the new headers. Something like this won't happen again, since ferror(), feof(), fileno(), and clearerr() are now functions as they ought to be.

Guido Flohr guido@freemint.de

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