BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Possible FastMM4 w/Optimization bug Goto page 1, 2, 3, 4  Next          BorlandTalk.com Forum Index -> Delphi Language BASM View previous topic :: View next topic   Author Message Jason Southwell Guest Posted: Wed Oct 12, 2005 7:08 pm    Post subject: Possible FastMM4 w/Optimization bug I switched to FastMM4 from nexusMM 3 due to a problem I had in a similar line of code with their MM and with optimizations turned on. FastMM 4 has been working much better for me, but now I'm running into one with it as well. Here is a link to a movie file showing the problem... 111MB AVI: http://www.streamload.com/deadserious/FastMM4.avi 15MB Flash: http://www.streamload.com/deadserious/FastMM4.swf You will see that the first time through, I build the project with Optimizations turned off. When I step through a loop, I see that TIWComboBox(c).items[i] returns the correct index from the items list. Next you will see me turn on Optimizations and rebuild the project. Now you will see that TIWComboBox(c).items[i] always returns the value of TIWComboBox(c).items[0] regardless to the value of i. I'm not beyond thinking that this is a problem is my code, but it seems very suspect to me that simply by flipping the Optimization flag, it will work or not work. This is almost identical to a problem I was previously experiencing with NexusMM 3 in a different section of code with a for loop. FWIW, with Nexus, the problem goes away if I change the for loop to a while loop. I haven't tried that yet with FastMM. Also, the problem does not exist using the stock RTL MM. At the end of the movie, I walk through the loop in the CPU window. Any ideas? -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Joe Bain Guest Posted: Wed Oct 12, 2005 7:27 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Jason Southwell wrote: Quote: I switched to FastMM4 from nexusMM 3 due to a problem I had in a similar line of code with their MM and with optimizations turned on. FastMM 4 has been working much better for me, but now I'm running into one with it as well. Here is a link to a movie file showing the problem... 111MB AVI: http://www.streamload.com/deadserious/FastMM4.avi 15MB Flash: http://www.streamload.com/deadserious/FastMM4.swf You will see that the first time through, I build the project with Optimizations turned off. When I step through a loop, I see that TIWComboBox(c).items[i] returns the correct index from the items list. Next you will see me turn on Optimizations and rebuild the project. Now you will see that TIWComboBox(c).items[i] always returns the value of TIWComboBox(c).items[0] regardless to the value of i. I'm not beyond thinking that this is a problem is my code, but it seems very suspect to me that simply by flipping the Optimization flag, it will work or not work. This is almost identical to a problem I was previously experiencing with NexusMM 3 in a different section of code with a for loop. FWIW, with Nexus, the problem goes away if I change the for loop to a while loop. I haven't tried that yet with FastMM. Also, the problem does not exist using the stock RTL MM. At the end of the movie, I walk through the loop in the CPU window. Any ideas? Try it with the default Delphi memory manager and you will get the same result. It is an optimization from the compiler. In a loop where the index does not matter, just the number of iterations the optimizer will change for loops from for i := 0 to size to for i := size downto 0. There are times that i is important that the optimizer does not recognize. Just turn it off for that part of the code with {$O-}. -------------- Joe Bain www.iegsoftware.com Back to top Jason Southwell Guest Posted: Wed Oct 12, 2005 7:50 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: Try it with the default Delphi memory manager and you will get the same result. It is an optimization from the compiler. In a loop where the index does not matter, just the number of iterations the optimizer will change for loops from for i := 0 to size to for i := size downto 0. There are times that i is important that the optimizer does not recognize. Just turn it off for that part of the code with {$O-}. As I stated in my first message, if I use the default memory manager, I do NOT get the same result. And the index des matter inside the loop... I'm using i to loop through items in a string list and I'm checking the value of that indexed string agaisnt another value then doing something with that result. There is NO reason it should be optimized out. -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Jason Southwell Guest Posted: Wed Oct 12, 2005 8:00 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: And the index des matter inside the loop... I'm using i to loop through items in a string list and I'm checking the value of that indexed string agaisnt another value then doing something with that result. There is NO reason it should be optimized out. In fact, this is the loop if you didn't see it in the AVI. You will see that i is certainly used within the loop... for i := 0 to TIWComboBox(c).Items.Count-1 do begin if Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'" ')] = '' then begin if TIWComboBox(c).ItemIndex < 0 then TIWComboBox(c).ItemIndex := 0; break; end else begin if (TIWComboBox(c).ItemsHaveValues) then begin if TIWComboBox(c).Items.ValueFromIndex[i] = Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'" ')] then begin TIWComboBox(c).ItemIndex := i; sReplace := TIWComboBox(c).Items.ValueFromIndex[i]; break; end; end else begin if TIWComboBox(c).Items[i] = Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'" ')] then begin TIWComboBox(c).ItemIndex := i; sReplace := TIWComboBox(c).Items[i]; break; end; end; end; end; -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Pierre le Riche Guest Posted: Wed Oct 12, 2005 8:18 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Hi Jason, Quote: Here is a link to a movie file showing the problem... 111MB AVI: http://www.streamload.com/deadserious/FastMM4.avi 15MB Flash: http://www.streamload.com/deadserious/FastMM4.swf When I click on the avi file I get a "An error occurred while processing your request." error, and you mentioned that the flash doesn't work so I didn't try it. Quote: I'm not beyond thinking that this is a problem is my code, but it seems very suspect to me that simply by flipping the Optimization flag, it will work or not work. This is almost identical to a problem I was Except for the initialization code FastMM4 is written entirely in assembler, so it shouldn't make a difference whether optimizations are on or not. The fact that it *does* make a difference suggests to me that perhaps there is a memory overwrite bug somewhere in the test application (or components). Have you tried using FastMM's FullDebugMode? FullDebugMode is aimed at helping to track down memory related bugs. Regards, Pierre Back to top Jason Southwell Guest Posted: Wed Oct 12, 2005 9:58 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: When I click on the avi file I get a "An error occurred while processing your request." error, and you mentioned that the flash doesn't work so I didn't try it. The hosting site seems to be having intermitant errors. Please try again in a bit. Quote: Except for the initialization code FastMM4 is written entirely in assembler, so it shouldn't make a difference whether optimizations are on or not. The fact that it does make a difference suggests to me that perhaps there is a memory overwrite bug somewhere in the test application (or components). Have you tried using FastMM's FullDebugMode? FullDebugMode is aimed at helping to track down memory related bugs. I have ran it with FullDebugMode and it reported no errors. Also, there are no memory leaks outside the standard Indy memory leaks. I had considered it was a memory overwrite issue, but there is no direct pointer/pchar etc access in my code, so it's unlikely. It may be happening in one of the used components... What would FullDebugMode show if one were occurring? -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Nicholas Sherlock Guest Posted: Thu Oct 13, 2005 5:26 am    Post subject: Re: Possible FastMM4 w/Optimization bug Jason Southwell wrote: Quote: You will see that the first time through, I build the project with Optimizations turned off. When I step through a loop, I see that TIWComboBox(c).items[i] returns the correct index from the items list. Next you will see me turn on Optimizations and rebuild the project. Now you will see that TIWComboBox(c).items[i] always returns the value of TIWComboBox(c).items[0] regardless to the value of i. This is just the debugger 'bug' that everyone seems to stumble across. Delphi optimizes loops to count down, but AFAIK it keeps a separate counter which counts upwards. The debugger shows the value counting down. In reality it is counting up. Add logging (outputdebugstring(inttostr(i))) to see. Cheers, Nicholas Sherlock Back to top Eric Grange Guest Posted: Thu Oct 13, 2005 6:08 am    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: I had considered it was a memory overwrite issue, but there is no direct pointer/pchar etc access in my code, so it's unlikely. Your code uses objects however, and these are pointers. If you store data in fields of an already freed object, you're likely to overwrite something else, and what that "something else" will be will depend on the MM and whatever was allocated in your code since the object was freed (the freed memory is bound to be reused at some point). If what you overwrite with another MM is unused data or still-unallocated memory, then the issue won't be visible but the overwrite is still there. Eric Back to top Jason Southwell Guest Posted: Thu Oct 13, 2005 11:17 am    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: Your code uses objects however, and these are pointers. Very true. Quote: If you store data in fields of an already freed object, you're likely to overwrite something else, and what that "something else" will be will depend on the MM and whatever was allocated in your code since the object was freed (the freed memory is bound to be reused at some point). Well, I can gaurantee that the TIWComboBox(c) is in fact a TIWComboBox and it is in fact newly created. I am reusing a local variable and c can be many different types of objects, but the correct object is newly created into that local variable just before the loop I posted. Quote: If what you overwrite with another MM is unused data or still-unallocated memory, then the issue won't be visible but the overwrite is still there. Well, I do not free the local variable before reassigning a new object to it. But that should not be an overwrite as it's essentially a new variable instance at that point. The old object that was in the variable was not freed, and should not be at this point. -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Jason Southwell Guest Posted: Thu Oct 13, 2005 11:19 am    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: This is just the debugger 'bug' that everyone seems to stumble across. Delphi optimizes loops to count down, but AFAIK it keeps a separate counter which counts upwards. The debugger shows the value counting down. In reality it is counting up. Add logging (outputdebugstring(inttostr(i))) to see. But it's not a debugger issue. WHen you run the app outside the debugger, 'i' still does increment, but the call to retrieve the string at index 'i' from the string list still retrieves 0. -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Eric Grange Guest Posted: Thu Oct 13, 2005 12:23 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: Well, I can gaurantee that the TIWComboBox(c) is in fact a TIWComboBox and it is in fact newly created. Can't see you code because the SWF is at too high a resolution and won't allow scrolling, but that the object is newly created isn't enough to shield you from side effects of overwrites completely, as dynamic allocations and destructions will happen during object creation, as well as usage of potentially corrupted data. One example would be a string whose size got corrupted: it was created with "Dummy", of Length=5, and then something replaced the 5 with a 50... code that alters the string will now risk altering whatever data lies beyond the initial string length, including a new object if a new object got allocated there. Similar issues can happen with arrays or all structures that store size or memory references. In your particular case, if you really want to know what happens, check the internal list and fields in the object (size, content, raw data content), are there really N times the same string? is it just some corrupted bounds check clamping your index? etc. Quote: The old object that was in the variable was not freed, and should not be at this point. Memory corruptions can affect parts of the code that are completely unrelated, both in terms of logic and time occurence. Eric Back to top Dan Downs Guest Posted: Thu Oct 13, 2005 12:33 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Just out of curiousity, try this: if Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'"')] = '' then begin if TIWComboBox(c).ItemIndex < 0 then TIWComboBox(c).ItemIndex := 0; // break; end else begin if (TIWComboBox(c).ItemsHaveValues) then begin for i := 0 to TIWComboBox(c).Items.Count-1 do begin if TIWComboBox(c).Items.ValueFromIndex[i] = Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'"')] then begin TIWComboBox(c).ItemIndex := i; sReplace := TIWComboBox(c).Items.ValueFromIndex[i]; break; end; end; end else begin for i := 0 to TIWComboBox(c).Items.Count-1 do begin if TIWComboBox(c).Items[i] = Defaults.Values[AnsiQuotedStr(dm.qryReportOptionsReplaceText.AsString,'"')] then begin TIWComboBox(c).ItemIndex := i; sReplace := TIWComboBox(c).Items[i]; break; end; end; end; end; I just shuffled the code a bit, no retyping, just cut and paste. I'm curious if your running into a compiler optimizing bug, since you only see it happen when optimiziation is turned on. Why it doesn't happen with the default MM I have no idea. DD Back to top Jason Southwell Guest Posted: Thu Oct 13, 2005 12:46 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Dan Downs wrote: Quote: I just shuffled the code a bit, no retyping, just cut and paste. I'm curious if your running into a compiler optimizing bug, since you only see it happen when optimiziation is turned on. Why it doesn't happen with the default MM I have no idea. It runs into the same problem of I incrementing but the retrieval from the stringlist always being index 0. -- Jason Southwell www.arcanatech.com Delphi & IntraWeb Components Consulting and Contracting Incident Based Support Back to top Dan Downs Guest Posted: Thu Oct 13, 2005 1:57 pm    Post subject: Re: Possible FastMM4 w/Optimization bug Quote: I just shuffled the code a bit, no retyping, just cut and paste. I'm curious if your running into a compiler optimizing bug, since you only see it happen when optimiziation is turned on. Why it doesn't happen with the default MM I have no idea. It runs into the same problem of I incrementing but the retrieval from the stringlist always being index 0. drats. Does it work with FastMM if you switch it to a while loop like you did for nexus? If so, I'm still learning towards something other than the MM. DD Back to top Ryan Mills Guest Posted: Thu Oct 13, 2005 2:18 pm    Post subject: Re: Possible FastMM4 w/Optimization bug After reading the entire thread I was wondering if the TIWCombobox component your using is from IntraWeb? If so what version of IW are you using? Could this be a known issue with IW? Ryan. On 12 Oct 2005 12:08:58 -0700, "Jason Southwell" <jason (AT) southwell (DOT) net> wrote: Quote: I switched to FastMM4 from nexusMM 3 due to a problem I had in a similar line of code with their MM and with optimizations turned on. FastMM 4 has been working much better for me, but now I'm running into one with it as well. snip Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> Delphi Language BASM All times are GMT Goto page 1, 2, 3, 4  Next Page 1 of 4   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.