Subject: Re: src/gnu/usr.bin/egcs/common
To: None <firstname.lastname@example.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
Date: 12/21/1999 22:37:46
>> [W]e still won't be able to change the size of FILE for a long time
>> -- so long as we require backwards compatibility with NetBSD from
>> three years ago.
> If this is true, it's only true because of (dynamic) linker issues.
> (some would say "bugs.")
> if the data definitions of the variables are in the shared library,
> and nothing uses their fields directly (or their fields can be used
> in a 'safe' way directly), you should be fine.
Recall what the historical definitions - the ones with which we'd need
to be compatible - are:
#define stdin (&__sF)
#define stdout (&__sF)
#define stderr (&__sF)
(The symbol name may vary; these are from stdio.h 1.30.) This means
that an old executable will contain a reference to __sF, regardless of
which filehandle is being used - the code will simply include an offset
for stdout and stderr.
The point is, this offset depends on sizeof(FILE)! The application's
compiled-in idea of sizeof(FILE) must match the layout of the __sF
array, or you're screwed.
And this is independent of the dynamic linker, as far as I can see.
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