Date: Sat, 8 May 2004 09:48:15 +0930 From: Malcolm Kay <malcolm.kay@internode.on.net> To: Henrik W Lund <henrik.w.lund@broadpark.no>, freebsd-questions@freebsd.org Cc: ckorves@hotmail.com Subject: Re: segmentation fault-- is my array too long? Message-ID: <200405080948.15164.malcolm.kay@internode.on.net> In-Reply-To: <409AAA48.50409@broadpark.no> References: <20040506190033.A45C616A5CF@hub.freebsd.org> <409AAA48.50409@broadpark.no>
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On Friday 07 May 2004 06:42, Henrik W Lund wrote: .... > malloc() is your friend! :-) > > --> double *ncost = malloc(sizeof (double) * persons * scens); <-- > > This ought to do the trick. Just remember to make sure that malloc > returns a valid pointer, otherwise you'll have another seg fault. > > I'm pretty sure you can adress the pointer like you do with the array > there (ncost[persons][0], etc...); if not, you can always do > ncost(sizeof(double) * persons + 0), etc... > > /* AMENDMENT!!! */ > In my haste, I totally forgot my pointer dereferencing. The correct way > to reference a pointer as a two dimensional array is, of course, thus: > > *(ncost + (sizeof(double) * persons) + 0)) = 0.00; You've still got it wrong! ncost increments in units of size equal to that which it points so it should be: *(ncost + person*scens + scen) where person is the first index and scen the second. or in the particular instance *(ncost + person*scens + 0) = 0.00; For easier to read code it would be better to use: double (*ncost)[scens] = malloc( persons * sizeof *ncost ); and dereference as: ncost[person][scen] or in particular ncost[person][0] = 0.0; And for the OP it is usual to write constants generated with #define in upper-case. It generally seems to help to make the code easier to follow. In this case: PERSONS instead of persons and SCENS instead of scens This also make the distinction between PERSONS and person more evident while retaining their implied connection. Malcolmhome | help
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