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From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Problem with gcc v2.953
Date:	3 Jan 2002 14:20:15 GMT
Organization:	Aachen University of Technology (RWTH)
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Francisco Pastor <Francisco DOT Pastor AT uv DOT es> wrote:

> selector) and after use the same offset ussing de %ds selector with the mov
> instruction. But in a interrupt handler %ss is different from %ds.

As far as I can see, the root of your problem is that you usually
can't write any interrupt handler in C, let alone C++, for exactly
this kind of reason: all code generated by the compiler will assume
SS=DS, which isn't true for interrupt handlers.  You need a wrapper
around the C(++) code written in assembly, or write the whole handler
in assembly right away.

> compiled with the file proof.cc have different result that if the name of
> the file is proof.c.

Note that inportb() is an "extern inline" function (in <pc.h>).  That
means most of its usages (if compiled with optimization turned on)
will not call the version found in libc.a at all.  One difference
between the various versions of compilers you're using (2.95.2
vs. 2.95.3, C++ vs. C) may very well be the decisions when to inline
and when not to.  Looking at GDB's "disassemble inportb" output won't
tell you anything about what actually happens: you have to disassemble
the code calling inportb(), instead.  Only if that does contain a call
to inportb(), the code of that routine matters.  

-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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