C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  .net memory allocation question          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message laniik Guest Posted: Fri Mar 11, 2005 11:30 am    Post subject: .net memory allocation question Hi, i have a program that runs fine on vc6. I am trying to port it to ..net 2003, but i am having some memory problems. here is the code that is causing me grief: struct Point3f { float x,y,z; }; --- snip int numLines=5; Point3f* pOuts = new Point3f[numLines]; --- causes a crash because new cannot allocate any more memory. i am not allocating any memory with the new or malloc operator before this line. also note: Point3f pOuts[10000]; //or 5 for that matter does not cause a crash. what is the difference between these two operators. i cannot use the latter because the size that i have to malloc changes dynamically. Thanks for the help! oliver [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Fri Mar 11, 2005 3:15 pm    Post subject: Re: .net memory allocation question laniik wrote: Quote: Hi, i have a program that runs fine on vc6. I am trying to port it to .net 2003, but i am having some memory problems. here is the code that is causing me grief: struct Point3f { float x,y,z; }; --- snip int numLines=5; Point3f* pOuts = new Point3f[numLines]; --- causes a crash because new cannot allocate any more memory. snip No, the crash is due to the code you didn't post. You may be quite certain that that other code is correct, but you're almost certainly wrong. (It *is* possible that the other code triggers a bug in the implementation, but this doesn't happen very often.) Have your rebuilt the entire program using VC++ 7.1 (VS.NET 2003) or are you using libraries that were compiled using VC++ 6? Ben. -- Ben Hutchings Having problems with C++ templates? Your questions may be answered by <http://womble.decadentplace.org.uk/c++/template-faq.html>. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top laniik Guest Posted: Sun Mar 13, 2005 12:36 pm    Post subject: Re: .net memory allocation question yes. i am aware that the code i posted is correct as i have done similar things many times. also my whole program is compiled using vc ..net 2003. i thought it might be something wrong with the heap/freestore settings as memory allocation works only at compile time. the other alternative is that there is somthing that i could be doing in the code before that that could be damaging the memory so that it cannot allocate. is this possible? the only memory related thing that I am doing in my code is this: struct Cluster { Point3f* points; }; int k=4; Cluster* cluster = new Cluster[k]; i am not however, allocating the points array before i do the allocation above. could this be causing a problem? as it know how big a Cluster is? The other confusing thing is that it works just find in VC6.0. Which leads me to believe that its not somthing in the code. Thanks a lot. Im trying to learn how all this allocation stuff works. Oliver [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Mon Mar 14, 2005 2:15 pm    Post subject: Re: .net memory allocation question laniik wrote: Quote: yes. i am aware that the code i posted is correct as i have done similar things many times. also my whole program is compiled using vc .net 2003. i thought it might be something wrong with the heap/freestore settings as memory allocation works only at compile time. the other alternative is that there is somthing that i could be doing in the code before that that could be damaging the memory so that it cannot allocate. is this possible? That is possible. A bug elsewhere may result in writing to memory referenced by an uninitialised or otherwise invalid pointer, and so corrupting the heap. Quote: the only memory related thing that I am doing in my code is this: struct Cluster { Point3f* points; }; int k=4; Cluster* cluster = new Cluster[k]; i am not however, allocating the points array before i do the allocation above. could this be causing a problem? as it know how big a Cluster is? That should not be a problem. However, reading the uninitialised "points" member of any of the newly-allocated Cluster objects results in undefined behaviour. In practice it is likely to be harmless unless and until you attempt to dereference it, e.g. evaluating cluster[0].points[0] is likely to crash the program. Quote: The other confusing thing is that it works just find in VC6.0. Which leads me to believe that its not somthing in the code. It is entirely possible and regrettably common for bugs that lead to "undefined behaviour" to be harmless in some circumstances but devastating in others. Quote: Thanks a lot. Im trying to learn how all this allocation stuff works. -- Ben Hutchings Having problems with C++ templates? Your questions may be answered by <http://womble.decadentplace.org.uk/c++/template-faq.html>. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ismail Pazarbasi Guest Posted: Mon Mar 14, 2005 11:55 pm    Post subject: Re: .net memory allocation question did you see anything on Output window? You may see something like "Heap address 0xbaadf00d blah blah..." there might also be a problem with the stack which would cause such a failure. check out your stack allocations as well. Ismail [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Junker Guest Posted: Tue Mar 15, 2005 8:38 pm    Post subject: Re: .net memory allocation question "laniik" <laniik (AT) yahoo (DOT) com> wrote Quote: yes. i am aware that the code i posted is correct as i have done similar things many times. also my whole program is compiled using vc .net 2003. i thought it might be something wrong with the heap/freestore settings as memory allocation works only at compile time. the other alternative is that there is somthing that i could be doing in the code before that that could be damaging the memory so that it cannot allocate. is this possible? the only memory related thing that I am doing in my code is this: struct Cluster { Point3f* points; }; int k=4; Cluster* cluster = new Cluster[k]; i am not however, allocating the points array before i do the allocation above. could this be causing a problem? as it know how big a Cluster is? The other confusing thing is that it works just find in VC6.0. Which leads me to believe that its not somthing in the code. Thanks a lot. Im trying to learn how all this allocation stuff works. Oliver If you are having memory allocation issues under Windows, and using the VC compilers, I'd recommend having a look at the debug CRT functions. They are quite good for tracking down memory corruption issues, although they will slow down execution of your program (as the heap is scanned for corruption). You should be able to find information about these functions on MSDN or the web, and the function to start looking at is the _CrtCheckMemory() function. If you call this function it will check the heap for corruption and fire an assert if the heap has been corrupted. Hope this helps, Dan. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ron Ruble Guest Posted: Wed Mar 23, 2005 10:43 pm    Post subject: Re: .net memory allocation question Ben Hutchings wrote: Quote: laniik wrote: <snip> Quote: The other confusing thing is that it works just find in VC6.0. Which leads me to believe that its not somthing in the code. It is entirely possible and regrettably common for bugs that lead to "undefined behaviour" to be harmless in some circumstances but devastating in others. Particularly porting from VC 6 to VC 7. That's the first upgrade in a -long- time that changed any of the longstanding non-compliant behavior in VC. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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