TYPE
LHdl = ^LPtr;
LPtr = ^LONGINT;
{$S Fill_Seg}
PROCEDURE FillWithData(h:Handle);
BEGIN
h^^ := 23;
END;
{$S Main}
PROCEDURE CanYouSpotTheProblem;
VAR
h :LHdl;
BEGIN
h := LHdl(NewHandleClear(Size));
FillWithData(h);
END.
I call this "Routines That Don't Move Memory, Most of the Time." The problem comes about
because of the hidden trap to LoadSeg. If all the code resources are preloaded, everything is OK.
But if they aren't, the call to FillWithData may cause a memory move, and h is not locked. This is
especially vile and nasty when, like us, you run in a very limited heap and unload your code
frequently.
I know that if you read Inside Macintosh Volume II very carefully this is clear. But most of the
interesting examples are the ones that are well documented but hard to catch.
Thanks for the example. You're right, of course; calling routines in other, unloaded segments can indeed move
memory. This is documented in various places, but unless you understand very clearly how your program
occupies memory and how the Segment Loader works, it's easy to overlook. Judicious use of a good heap
scramble/purge will catch this one before it catches you.
Thanks for writing!
--Dave Johnson
WHERE IN THE WORLD(SCRIPT)?
I was looking for the WorldScript folder on Issue 12's Developer CD, "Wayne's GWorld" (Dev.CD
Nov/Dec 92). According to the Contents Catalog stack, the WorldScript folder should be found in
this path: Dev.CD Nov/Dec 92: System Software: WorldScript. But it's not there. I talked with a
friend of mine who has the same CD, and he found the folder where it's supposed to be. We
checked our CDs and found out that his says 564.6 MB on disc, 69.7 MB available, while mine says
555.5 MB on disc, 78.9 MB available. What's going on?
--Toru Kawate
P.S. Thank you for the fine journal and CD. I really enjoy them.
I received Issue 12 of develop with the Nov/Dec 1992 Developer CD Series disc. I enjoy the Developer
CD but had the following trouble: I used the Contents Catalog on the CD and found the title"WorldScript." But I didn't find the folder at the pathname Dev.CD Nov/Dec 92: System Software:
WorldScript.
--Hirokazu Yaguchi
At the last minute, WorldScript was pulled from the CD accompanying develop, but there wasn't enough
time to remove it from the Contents Catalog. WorldScript did, however, remain on the Developer CD Series
disc received monthly by members of Apple's developer programs.
The reason for this is tied in with why develop now has its own CD, separate from the Developer CD Series
disc; for details, see the editorial on page 2.
--Caroline Rose
WHEN TO EXPECT DEVELOP
Sorry to disturb you, but because I've had problems with my subscription (two copies, no copies) --
which I've worked out, I think, with the DEV.SUBS people -- I'm wondering: Is there some sort of
publication schedule available that will allow me to fret about this without disturbing anyone? ("Gee,
it's two weeks past when this should be out . . . what am I missing out on?!")
Y'all are doing a fine job. Just be sure to run your issues through a Quark SmugCheck to keep the
content only kinda wacky and smug without being too much that way.
Thanks!
--J. C. Burns
I'm sorry you've had subscription problems, but I'm grateful that you pursued them with DEV.SUBS rather than sending an AppleLink to CROSE or DEVELOP; many developers make the mistake of contactingdevelop staff with these problems, but it's really out of our realm. We are, however, doing our best to make the problems go away.
If you're located in the U.S., you should normally receive develop around the first of March, June, September, and December. (If you're outside the U.S., it's hard to say, because develop might need to wait for other materials to be merged into the same mailing.)
Thanks for the tip on SmugCheck; it's just what we need!
--Caroline Rose
M.TN.DESIGNATIONS
I notice you still add the numbers in references to Tech Notes. If dropping the numbers were such
progress, that wouldn't be necessary. And the new alphanumeric reference codes are not used.
I'm a technical person who is used to abbreviations everywhere for conciseness. Besides, citing with
full titles adds noise and a lot of repetitiveness.
--Peter Fink
We decided to include the old numbers in references to Tech Notes to help out those people who like to use hard copy but still have the numbered versions. We'll stop doing that once enough time has elapsed that we expect everyone will have the new, unnumbered versions.
For a variety of reasons, we decided not to include the new designations, such as "M.PT.StandAloneCode," which identify the category/folder for each Note. We figured people could find the Notes in the new file organization easily enough -- a Note on QuickTime is in the QuickTime folder, right? But we've since realized that the category isn't always obvious. So starting with this issue we refer to Notes by category -- for example, "See the Macintosh (Platforms & Tools) Technical Note, 'Stand-Alone Code, ad nauseam.'"
Many developers simply look up specific notes in the various Tech Note indexes, and don't use the special designations at all. For those who do use them, they've been improved to correlate more closely to the Notes' titles; for more on this and other recent Tech Note improvements, see the box on this page.
We're always open to suggestion, but so far you're the only one to mention this. If others reading this reply
have similar feedback, I hope they'll let us know.
--Caroline Rose
On the August 1992 Developer CD Series disc, the new organization of Macintosh Technical Notes made its debut. Since then, we've been listening for suggestions for improvement. The vast majority of the feedback has been positive, but you did point out a few areas for attention:
Many of you have asked how to quickly locate the most recently written and updated Tech Notes. On the CD, aliases to the latest Notes can always be found in the "What's new on this CD?" folder. Using the Finder's View by Date option on the category folders is a handy way to see the most recent updates.
Also, please note that to group related information more logically, we've integrated Q&As into the Tech Note library. Q&As appear at the beginning of every section in the print version, and have the label "Essential" in the electronic version (or a different label if you've changed that label name on your system).
Many of you noticed that the Tech Note and Q&A stacks have gone away: the Tech Note library is now available in Apple DocViewer format (as well as Microsoft Word files). You should find the searching and viewing in Apple DocViewer much more usable; please check it out.
These changes should make information much easier to find. As always, if you have suggestions or ideas for improving the Tech Note library, please let me know!
Thanks to Doug McKenna, the author of Resorcerer, for pointing out these problems.
WE WORRY WHEN YOU DON'T WRITE We welcome timely letters to the editors, especially from readers reacting to articles that we publish in develop. Letters
should be addressed to Caroline Rose (or, if technical develop-related questions, to Dave Johnson) at Apple Computer,
Inc., 20525 Mariani Avenue, M/S 75-2B, Cupertino, CA 95014 (AppleLink CROSE or JOHNSON.DK). All letters should
include your name and company name as well as your address and phone number. Letters may be excerpted or edited for
clarity (or to make them say what we wish they did). *
Send your feedback on Tech Notes or Sample Code to Neil at AppleLink NMDAY or on the Internet at nmday@apple.com.*
