leeke@glacier.STANFORD.EDU (Steven D. Leeke) (09/28/88)
Let's suppose I want to load a CODE segment from some other file and call it as a C function - making sure it is declared as a C main and pass it the correct parameters - one of which is a table of entry points into the program that is loading it - the "main" program. The entrypoints are setup as an array of Ptr's which are created dynamically just before the call. e.g. entryPoints = NewPtr(sizeof(ProcPtr)*NoOfEntries); if (entryPoints != NULL) { entryPoints[0] = <function name>; ... }; LSC reqires me to use their RememberA4/SetupA4 stuff on entry in the CODE segment and RestoreA4 on exit to get at the globals (if any) in the CODE segment - so I do. e.g. the CODE segment's main looks like: void main(p1,p2,p3,...,entryPoints) { RememberA4(); SetupA4(); /* Intervening code...including jumps back into the "main" program - see below. */ RestoreA4(); }; What I want to know is if A5 is getting bashed when I call the CODE segment? I am able to load the segment, lock it, dereference it and call it successfully e.g.: code = GetResource(zzzz,yyy); if (code != NULL) { HLock(code); (**code)(p1,p2,p3,...,entrypoints); HUnlock(code); }; Then, I use the array of entrypoints to call various fctns (C) in the "main" program, e.g.: (*entryPoints[0])(); This seems to work well until I try to draw something from within the "main" program (I don't draw in the code segment) - usually activating or updating a window when a dialog the CODE segment loaded is being drawn. So what is it? Is A5 getting bashed in the CODE segment? I am using a project with only the MacTraps library for the CODE segment. This makes me think that as soon as I call the code segment the QuickDraw globals are getting bashed since MacTraps defines them. e.g. A5 is corrupted. This is my prime culprit since crashing only occurs when something is drawn. I've tried to use SetupA5 right after SetupA4 when I start my CODE segment, for what it's worth, but it doesn't seem to make a difference. I'm not an experienced ASM hacker period - especially on the Mac. Any help would be appreciated, Steve Leeke
tim@hoptoad.uucp (Tim Maroney) (09/29/88)
In article <17742@glacier.STANFORD.EDU> leeke@glacier.UUCP (Steven D. Leeke) writes: >LSC reqires me to use their RememberA4/SetupA4 stuff on entry in the >CODE segment and RestoreA4 on exit to get at the globals (if any) in >the CODE segment - so I do. e.g. the CODE segment's main looks like: > >void main(p1,p2,p3,...,entryPoints) >{ > RememberA4(); > SetupA4(); > /* ... */ > RestoreA4(); >}; Look at page 85 of the User's Manual. You need to call RememberA0(), not RememberA4(). They're very different macros. Things are getting trashed because A4 is set to something silly, so all your global accesses are writing into random memory locations. >This seems to work well until I try to draw something from within the >"main" program (I don't draw in the code segment) - usually activating >or updating a window when a dialog the CODE segment loaded is being drawn. That's probably just the way it happens; change a few variables and you might have problems with drawing controls or dragging windows instead. But if you really want to know whether A5 is problematic, just drop into MacsBug or TMON at the beginning of the main program callback routine, and see if A5 is the same as the low-memory global CurrentA5. I'm pretty sure there is no reason to explicitly set A5 to CurrentA5 inside the callback routine, since the code resource shouldn't modify A5. But if you want, setting A5 to CurrentA5 in the callback routine couldn't hurt. >I've tried to use SetupA5 right after SetupA4 when I start my CODE segment, >for what it's worth, but it doesn't seem to make a difference. I'm not >an experienced ASM hacker period - especially on the Mac. This, I think, confirms my feelings that your problems are with A4. -- Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim "I see little divinity about them or you. You talk to me of Christianity when you are in the act of hanging your enemies. Was there ever such blasphemous nonsense!" - Shaw, "The Devil's Disciple"