Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!amdahl!kevin From: kevin@amdahl.uts.amdahl.com (Kevin Clague) Newsgroups: comp.sys.amiga.tech Subject: Re: Need help with disapearing libraries!! Summary: Acheived true enlightenment!! Keywords: exec CloseLibrary() low-memory programming-error disk-resident Message-ID: <94VHE83H1N1010XR5XU@amdahl.uts.amdahl.com> Date: 6 Jul 88 16:03:38 GMT References: <94Y1F20q831010pYHiE@amdahl.uts.amdahl.com> <736@applix.UUCP> Organization: Amdahl Corporation, Sunnyvale, CA 94086 Lines: 65 [] >In article <94Y1F20q831010pYHiE@amdahl.uts.amdahl.com> kevin@amdahl >>What kind of programming mistakes can I make that would cause libraries >>to be closed without CloseLibrary()'ing them explicitly? >>Db usually indicates that the last function I've called is SPTieee(), Thoughtfully Scott Evernden replies... > I'll bet you that your stack isn't large enough. Bump your > stack and see if it still happens... > -scott Good try, but the problem is more subtle than that. After lots of soul searching last night, I reached true enlightenment! The GURU would be proud. I share the solution with the net in hopes that it may help other Amiga neophites.... The facts: 1. I use Manx 3.6. 2. Manx automaticaly opens and closes required math libraries. Manx does this on a demand basis. On every math operation that requires an Amiga library, manx checks the appropriate library pointer (e.g. MathIeeeDoubBas). If it is NULL, then Manx opens the library and sets the library pointer to the result of OpenLibrary(), and then performs the math library function call. 3. Manx does not print error messages or quit when it can't open disk resident libraries (like MathIeeeDoubBas) 4. I explicitly OpenLibrary() the libs I need, so I can give the user meaningful error messages about missing libs. Since I get the lib open, Manx does not have to OpenLibrary() it. 5. When I'm done, I CloseLibrary() the libraries, but I don't (didn't) set the lib pointer to NULL, so Manx's cleanup code CloseLibrary()'s it also. The lib is now closed twice, and the lib_OpnCnt is -1. 6. The next time I run my program and open the libs, the lib_OpnCnt is 0 which means that it can be removed by exec when the system runs out of memory. Boom!! Things to note: 1. Manx does not handle missing disk resident libraries well. 2. Exec does not ever check for CloseLibrary()ing too many times. This is not a surprise. The bug one seems very subtle, and has been around in my code for more than a year. This is one of those bugs that can easily mess up other program's execution. Sorry to waste net bandwidth with my specific bug, but because it seems soooo subtle, I figured I'd share it. -kevin -- UUCP: kevin@amdahl.amdahl.com or: {sun,decwrl,hplabs,pyramid,seismo,oliveb}!amdahl!kevin DDD: 408-737-5481 USPS: Amdahl Corp. M/S 249, 1250 E. Arques Av, Sunnyvale, CA 94086 [ Any thoughts or opinions which may or may not have been expressed ] [ herein are my own. They are not necessarily those of my employer. ]