accessing long pointer safearray structure in dll
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Thread: accessing long pointer safearray structure in dll

  1. #1
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    Post accessing long pointer safearray structure in dll

    hello friends,

    i am debugging a dll file for an application and i am getting some problem in accessing the safearray structure in the dll file.
    the application wes developed in vc++ 2005 now upgrading it to vc++2008.
    For the front end there using vb script 2005.

    so the problem is i am passing a structure type array (that is having data fatched from the ole database) to a dll as a LPSAFEARRAY parameter,when i executing the front end, the dll is accessing properly but when its going to allocate the memory its sending the error report (other memkry corrupted) from the backend. but when i compiling the backend dll its not giving any error.and when i trace the each and every line of the dll from the front end got to know that the problem is while its allocating the memory. i am giving a few details of the coding please someone help me to figure this out.

    vb code ::
    Code:
    structure configtable
    public pid as long
    public configid as long
    public wordno as long
    public unit as string
    public maxval as single
    end structure
    declearation of array in vb::

    Code:
    public para() as configtable
    calling the dll function in vc++ ::

    Code:
    databaseinitialization(para,apppath)
    the structure in dll::
    Code:
    typedef struct
    {
    int pid;
    int configid;
    int wordno;
    LPVOID unit;
    float maxval;
    }PARAMETERS;
    function where i got the error ::
    Code:
    databaseinitialization(LPSAFEARRAY FAR *prtPARAMDATA, LPSTR path)
    {
    
    PARAMETERS *paraTABLE;
    
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound->cElements); //the error line
    }
    i have also tried by giving like but den its givig some while compiling the dll:


    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA).rgsabound[0].cElements);
    or

    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * ptrPARAMDATA->rgsabound->cElements);
    but den its showing :
    Code:
    error C2227:left of '->rgsabound' must point to class/struct/union/generic type.
    
    error C2227:left of '->cElements' must point to class/struct/union/generic type.
    full code is not given but this line in the databaseinitialization is not executing.waiting for reply...
    Last edited by sumlal; March 24th, 2014 at 05:49 AM.

  2. #2
    VictorN's Avatar
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    Re: accessing long pointer safearray structure in dll

    Please, use Code tags while posting code snippets. Otherwise your code becomes absolutely unreadable! See the Announcement: Before you post....

    Why do you use malloc in c++ code?
    Why don't you use SafeArrayAllocData?
    Victor Nijegorodov

  3. #3
    Join Date
    Mar 2014
    Posts
    17

    Re: accessing long pointer safearray structure in dll

    hello friends,

    i am debugging a dll file for an application and i am getting some problem in accessing the safearray structure in the dll file.
    the application wes developed in vc++ 2005 now upgrading it to vc++2008.
    For the front end there using vb script 2005.

    so the problem is i am passing a structure type array (that is having data fatched from the ole database) to a dll as a LPSAFEARRAY parameter,when i executing the front end, the dll is accessing properly but when its going to allocate the memory its sending the error report (other memkry corrupted) from the backend. but when i compiling the backend dll its not giving any error.and when i trace the each and every line of the dll from the front end got to know that the problem is while its allocating the memory. i am giving a few details of the coding please someone help me to figure this out.

    vb code ::
    Code:
    structure configtable
    public pid as long
    public configid as long
    public wordno as long
    public unit as string
    public maxval as single
    end structure
    declearation of array in vb::

    Code:
    public para() as configtable
    calling the dll function in vc++ ::

    Code:
    databaseinitialization(para,apppath)
    the structure in dll::
    Code:
    typedef struct
    {
    int pid;
    int configid;
    int wordno;
    LPVOID unit;
    float maxval;
    }PARAMETERS;
    function where i got the error ::
    Code:
    databaseinitialization(LPSAFEARRAY FAR *prtPARAMDATA, LPSTR path)
    {
    
    PARAMETERS *paraTABLE;
    
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound->cElements); //the error line
    }
    i have also tried by giving like but den its givig some while compiling the dll:


    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA).rgsabound[0].cElements);
    or

    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * ptrPARAMDATA->rgsabound->cElements);
    but den its showing :
    Code:
    error C2227:left of '->rgsabound' must point to class/struct/union/generic type.
    
    error C2227:left of '->cElements' must point to class/struct/union/generic type.
    full code is not given but this line in the databaseinitialization is not executing.waiting for reply...

  4. #4
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    17

    Re: accessing long pointer safearray structure in dll

    i am extremely sorry that i didn't use code block last time.

    i have tried the SafeArrayAllocData function but i don't know how to initialize the allocated memory to the PARATable, as its given :

    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound->cElements);
    and when i tried this code like its giving illigal use of expression :

    Code:
    paraTABLE=SafeArrayAllocDescriptor(PARAMETERS,ptrParamData)

  5. #5
    VictorN's Avatar
    VictorN is online now Super Moderator Power Poster
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    Re: accessing long pointer safearray structure in dll

    Why malloc?
    use SafeArrayAllocDescriptor and SafeArrayAllocData instead.
    And BTW, using Code tags without proper code indentation does not make any sense!
    Victor Nijegorodov

  6. #6
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    Re: accessing long pointer safearray structure in dll

    please follow the full function of databaseinitialization. the previous developer write this code in vc++ 2005 , and while i debugging in 2008 its not executing.

    Code:
    void _stdcall DatabaseInitialization(LPSAFEARRAY  FAR *ptrParamData, LPCSTR path)
    {
    	
    	PARAMETERS		 *ParaFiles        , 
    		             temp	      = {0};
    
    	
    	unsigned int     index = 0,stickyindex  =   0;
    	int              superfrmcnt  =   0;
     					
        char			 *paraname         ,
    	    	   		 *unitname         ,
    	    			 *alias            , 
    					 //SpdFilePath[1024] ,
    	                 Dfdr[100] = {'\0'};
    	unsigned short int        *refreshmemory    ;
     /******Global Parameters initialisations*************/
    
    	DfdrType	= datalength; 
    	
    /*	if((fpmahesh = fopen( "MaheshDebug.txt", "w" )) == NULL )
    	{
    		MessageBox(NULL," Could not open MaheshDebug.txt file.","Error !",MB_OK );
    		exit(0);
    	}*/
    	
    	itoa( DfdrType, Dfdr, 10 );
    	
    	PARATable = (PARAMETERS *) malloc (sizeof(PARAMETERS) * (*ptrParamData)->rgsabound->cElements);//error line
    	
    	Frame.subframe1 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        Frame.subframe2 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        Frame.subframe3 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    	Frame.subframe4 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    
    	prevFrame.subframe1 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        prevFrame.subframe2 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        prevFrame.subframe3 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    	prevFrame.subframe4 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    
    	tempFrame.subframe1 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        tempFrame.subframe2 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        tempFrame.subframe3 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    	tempFrame.subframe4 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    
    	tempFrame1.subframe1 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        tempFrame1.subframe2 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        tempFrame1.subframe3 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    	tempFrame1.subframe4 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    
        refreshmemory   = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
        for (index = 0; (int)index < DfdrType ; index++ )
        {
    		refreshmemory[index] = 0;
    	}
    		
        for (superfrmcnt = 0 ; superfrmcnt < 16 ; superfrmcnt++)
    	{
    		SFrame.frames[superfrmcnt].subframe1 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    		SFrame.frames[superfrmcnt].subframe2 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    		SFrame.frames[superfrmcnt].subframe3 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
    		SFrame.frames[superfrmcnt].subframe4 = (unsigned short int *) malloc (sizeof(short int ) * DfdrType);
            
    		memcpy(SFrame.frames[superfrmcnt].subframe1,refreshmemory , sizeof(short int ) * DfdrType);
    		memcpy(SFrame.frames[superfrmcnt].subframe2,refreshmemory , sizeof(short int ) * DfdrType);
    		memcpy(SFrame.frames[superfrmcnt].subframe3,refreshmemory , sizeof(short int ) * DfdrType);
    		memcpy(SFrame.frames[superfrmcnt].subframe4,refreshmemory , sizeof(short int ) * DfdrType);
    
    	}
     
    	MemoryFreeFlag[0] = 1 ;
    
        free(refreshmemory);//a function call
    
    
    	TotalParam = (*ptrParamData)->rgsabound->cElements;//error line
    
    	ClearParaTable( TotalParam );
    	
    	ParaFiles=(PARAMETERS *)((*ptrParamData)->pvData);
       
    
    	for (index = 0;index <((*ptrParamData)->rgsabound->cElements); index++,ParaFiles++)//error line
    	{
    	  
    		unPackVBStr(ParaFiles->paraname  , &paraname);
    		unPackVBStr(ParaFiles->aliasname ,    &alias);
    		unPackVBStr(ParaFiles->units     , &unitname);
        
    		temp.pid			= ParaFiles->pid		 ; 
    		temp.configid		= ParaFiles->configid	 ;
    		temp.wordno			= ParaFiles->wordno		 ;
    		temp.maxval			= ParaFiles->maxval		 ;
    		temp.units			= unitname		    	 ;
    
    	  
    		PARATable[index]    = temp;
    
    //		fprintf( fpmahesh, "%s\t%s\t%s\t%d\t%d\t%d\n ", 
    //							temp.paraname, temp.aliasname, temp.units, temp.pid, temp.configid,
    //							temp.wordno );
    	}
    	// ** For copying sticky information ** // 
    
    	ConfigID			= temp.configid			 ;		
    
    	
    	//fclose( fpmahesh );
    }
    so where ever the line has been used its not showing error in dll but not executing in background.

    what could be the other option that i can use instead of that line.
    Last edited by sumlal; March 24th, 2014 at 06:45 AM.

  7. #7
    VictorN's Avatar
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    Re: accessing long pointer safearray structure in dll

    Quote Originally Posted by sumlal View Post
    Code:
    databaseinitialization(LPSAFEARRAY FAR *prtPARAMDATA, LPSTR path)
    {
    PARAMETERS *paraTABLE;
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound->cElements); //the error line
    }
    i have also tried by giving like but den its givig some while compiling the dll:


    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA).rgsabound[0].cElements);
    or

    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * ptrPARAMDATA->rgsabound->cElements);
    but den its showing :
    Code:
    error C2227:left of '->rgsabound' must point to class/struct/union/generic type.
    
    error C2227:left of '->cElements' must point to class/struct/union/generic type.
    full code is not given but this line in the databaseinitialization is not executing.waiting for reply...
    The error is, I guess, because the ptrPARAMDATA and prtPARAMDATA are two different identificators.
    Victor Nijegorodov

  8. #8
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    Re: accessing long pointer safearray structure in dll

    As victor said in his post #4, please use proper indentation when posting code so that it's readable.

    This is c rather than c++ code. When using malloc you need to check the assigned variable for NULL to see if memory has actually been assigned or not.

    Before the call the malloc is made, what is the value of (*ptrParamData)->rgsabound->cElements ? If this is not a sensible value then malloc will probably fail but you aren't checking for that as I mentioned above.

    Have you tried
    Code:
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound[0].cElements);
    Last edited by 2kaud; March 24th, 2014 at 07:21 AM.
    All advice is offered in good faith only. You are ultimately responsible for effects of your programs and the integrity of the machines they run on.

  9. #9
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    Re: accessing long pointer safearray structure in dll

    Quote Originally Posted by sumlal View Post
    so where ever the line has been used its not showing error in dll but not executing in background.
    First of all, you have to explain your solution architecture clearly and unambiguously. I have to admit that I totally lost in your frontends, backends, showing errors and executing in backgrounds.

    If I were you, I would make an isolated sample replicating your problem and demonstrating what calls what, and posted it here on the forum. The sample must not access any real database, you just fill the array with some pre-defined data and see how it comes to your c++ dll.

    If I understand you correctly, the sample is to consist of two dlls, vb and c++, and some launcher app for driving vb dll.
    Best regards,
    Igor

  10. #10
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    Re: accessing long pointer safearray structure in dll

    First of all, you have to explain your solution architecture clearly and unambiguously. I have to admit that I totally lost in your frontends, backends, showing errors and executing in backgrounds.

    If I were you, I would make an isolated sample replicating your problem and demonstrating what calls what, and posted it here on the forum. The sample must not access any real database, you just fill the array with some pre-defined data and see how it comes to your c++ dll.

    If I understand you correctly, the sample is to consist of two dlls, vb and c++, and some launcher app for driving vb dll.
    may be sir i can,t able to explain the problem properly in this code, i have just joined as a trainee in an organization and don't have that much experience to dealing with such type of error, and also because i am aslo not getting y this error is comming..the application is consist of several dll in the back-end (mainly in vc++) and the luncher application is in vb, and yes there are some vb dll also but no problem with them.

    when i releasing the dll its working smoothly with the above code (posted at #1) but with application its not working properly. so,to track the error i included a massegebox after every statement in that dll and thus i got to know which line is having he problem.

    what ever i have studied this problem i am still having some confusion in the concept,

    If u see in the above function they have declear a structure array in vb
    Code:
    structure configtable
    public pid as long
    public configid as long
    public wordno as long
    public unit as string
    public maxval as single
    end structure
    
    public para() as configtable
    and they passed the array to the dll function where the "datainitialization()" is present in a dll and this function is having no connectivity with others dll
    Code:
    databaseinitialization(para,apppath)
    at the next step in dll they accessing the parameter as LPSAFEARRAY
    Code:
    void _stdcall databaseinitialization(LPSAFEARRAY FAR *prtPARAMDATA, LPSTR path)
    they are using that LPSAFEARRAY to allocate the memory as
    Code:
    PARAMETERS *paraTABLE;
    
    paraTABLE=(PARAMETERS*) malloc (sizeof(PARAMETERS) * (*ptrPARAMDATA)->rgsabound->cElements); //the error line
    so the question is they are not assinging any value to the "cElements" before this statement but they are using this variable to allocate memory , is this possible to allocate memory like this ? and if yes then how ? i am not that much familiar with SAFEARRAY concept so i am having confusion with that.

    and then if u can see they are allocating memory and initialize that memory to another structure variable "PARAMETERS" which is defined in the same dll as
    Code:
    typedef struct
    {
    int pid;
    int configid;
    int wordno;
    LPVOID unit;
    float maxval;
    }PARAMETERS;


    waiting for reply.....
    Last edited by sumlal; March 26th, 2014 at 02:55 AM.

  11. #11
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    Re: accessing long pointer safearray structure in dll

    sorry sir, that was my mistake only. it was a typing mistake while i was writing in this forum.

  12. #12
    VictorN's Avatar
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    Re: accessing long pointer safearray structure in dll

    Quote Originally Posted by sumlal View Post
    sorry sir, that was my mistake only. it was a typing mistake while i was writing in this forum.
    Yes, you did a lot of mistakes. One of them was what I wrote you in the post#7.
    Another one is you got rid of proper code indentation.
    The next - you got rid of proper text punctuation and spell checking.
    Victor Nijegorodov

  13. #13
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    Re: accessing long pointer safearray structure in dll

    Quote Originally Posted by VictorN View Post
    Yes, you did a lot of mistakes. One of them was what I wrote you in the post#7.
    Another one is you got rid of proper code indentation.
    The next - you got rid of proper text punctuation and spell checking.
    Thank u for correcting me with all this things. but still i couldn't found any way to resolve the problem. If u can understand the problem can u help me out ..!! u can follow the post#6 and post#10.

  14. #14
    VictorN's Avatar
    VictorN is online now Super Moderator Power Poster
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    Re: accessing long pointer safearray structure in dll

    Have you already fixed the "mistake" with ptrPARAMDATA and prtPARAMDATA variables I mentioned in the post#7?
    Victor Nijegorodov

  15. #15
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    Re: accessing long pointer safearray structure in dll

    Quote Originally Posted by sumlal View Post
    waiting for reply.....
    You may be, but you're not going to have any certain answer until you provide us with a sufficient information I asked you about. Why is it so important to provide a concise and compilable project?

    First of all, by composing one you eliminate any unnecessary "informational noise" and let us focus specifically on your problem.

    Second, having a compilable and runnable solution people here can see all the tiny details you may consider unimportant while those are important in fact. E.g., you mention VB. What version of VB? Is it VB6.0 or VB.NET? Or other thing, you show us how the function is declared in C++ dll but never do that for VB side. I'm sure there might be other points you failed to report.

    So the bottom line is: you are to provide a small compilable project or projects that together replicate your issue.

    PS. There may be Third as well. The issue have good chances to be solved right when you compose a small project replicating it, just because you "peel the peach." Trust me, I know what I'm talking about as I do this for decades.
    Best regards,
    Igor

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