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Conference hydra::amiga_v1

Title:AMIGA NOTES
Notice:Join us in the *NEW* conference - HYDRA::AMIGA_V2
Moderator:HYDRA::MOORE
Created:Sat Apr 26 1986
Last Modified:Wed Feb 05 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:5378
Total number of notes:38326

3622.0. "MEMGUARD alert messages" by ENOVAX::BARRETT (Computers will ruin your life) Tue Mar 27 1990 15:10

    Ever since I've installed MEMGUARD on my system, I've caught several
    programs that have attempted changing the values of low memory
    locations. Most of them "feel" like they could have contributed to
    random GURU's I have had a various points. I thought it would be good
    to devote a topic to listing these programs that have shown up. The
    most common one for me is
    
    OnlinePlatinum!
    
    It tries to write a "10101010" to location 40 on startup, and will crash
    if prevented from doing this. This could help explain why I've had
    crashes when I used the system while a download was going on - especially
    when this seems to be the only program that I have this problem with.
    
    I'm not sure if it's C-Show or MyMenu that also tries
    to change low memory -- as it's not clear who's at fault when I see
    this one and I use both programs.
    
T.RTitleUserPersonal
Name
DateLines
3622.1LEDS::ACCIARDILarger than life, and twice as uglyTue Mar 27 1990 23:254
    
    Sculpt 3DXL trys to trash low memory.  Thank you, Memguard.
    
    Ed.
3622.2WELMTS::FINNISPeter Finnis at WelwynWed Mar 28 1990 09:146
    Is memguard better than GOMF ?
    What sort of alert does it give , can you continue operation after
    it has detected a rogue program trashing low mem ?
    
    			Pete
    
3622.311SRUS::MARKWaltzing with BearsSat Mar 31 1990 12:1625
Re: .2

	When it detects a program trashing low memory, it gives an alert
which contains the address, and the new value.  It gives you the option 
to leave it alone, or put the original value back.

Re: MemGuards effectivness

	I started it up last night.  I wanted some evidence that it was
working, so I wrote a program to change a value in low memory.  Since
the MemGuard documentation said it was particularly important to protect
location 4, that seemed like a good place to trash to see results.  When
run, the following program will crash the system and no MemGuard alert
will be displayed:

main() {
int *p;

p = (int *) 4;
*p = 1432;  /* a value I chose at random. */
}

	Changing other locations (I tried 14, as well) does bring up memguard.

Mark
3622.4MANX C ... ggggggggrrrrrrrrrrr!!!!!!!!!NAVIER::LONGWed Apr 04 1990 09:595
	The Assembler phase of MANX C V3.4a as my memory drops below the
	2 meg available mark ( 3 meg total with 1 meg chip )!!!
        Address 0C is played with and must be saved.

	Dick