Hi Eric,
thanks for help,
Eric Auer wrote:
>
> Hi Franta,
>
>> struct dosemu_detect {
>> char magic[8];
>> unsigned char ver[4];
>> };
>> static struct dosemu_detect far *p = (void far*) 0xF000FFE0;
>
> Note that the way how you create far pointers can differ
> between compilers. In particular, with any 32 bit memory
> model, things would look quite differently. Just saying.
Pointers and things around them are for me still a little
incomprehensible ;)
>> char magicexp[]="$DOSEMU$"; // expected string when on
>> DOSEMU
>>
>> if (strcmp(p->magic, magicexp)) // p->magic == "$DOSEMU$" ?
>
> You cannot strcmp this because the string is no C style
> string with a NUL character at the end. You could use
> strncmp(string1, string2, 8) to compare only the first
> eight bytes, which will probably work fine for you :-)
But 'magicexp' is null-terminated string, yes? Then comparison
should stop at its length (or before, when p->magic is different
or has null-byte before strlen(magicexp) ), I suppose that.
And I tried to use some as
strncmp(p->magic, magicexp, strlen(magicexp))
too and it also was not working.
But I definitely think it has some with memory models or needs
for same data segment for both strcmp() arguments - until now
I've noticed OpenWatcom C library has functions for far pointer
arguments ( _fstrcmp/_fstrcat/_fstrlen/_fstrstr/...) and when
I use '_fstrcmp' instead of 'strcmp', then detection works well.
>> (I'm using tiny memory model and link .COM instead of .EXE, for
>> minimalize program size)
>
> PS: I do not know if int 0xe6 is really deprecated. Anybody?
In my first mail referenced FreeDOS thread:
http://marc.info/?l=freedos-dev&m=88425176918117&w=2
Hans Lermen wrote about it:
"This detection method is abandoned, future DOSEMU versions will
even (intentionally) refuse to run, when INTE6 AH=0 is called."
>> (and curiously, in referenced thread deprecated method Int 0xE6 AH=0
>> still /after ~17 years/ is supported and seems be working well)
Maybe DOSEMU development team changed this decision (or simply
leave it here).
--
Thanks, Franta Hanzlik
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