C / C++ / MFC

Re: First-chance exception ... access violation ... pointer issue

16-Jun-07 20:18

i have just finished compiling my application and everything is in order, but when i run it to test the different features, there is a runtime error...and it deals with access violation, hence a pointer issue. i need help fixing this and following is the call stack:

int wNode::getId() <br />
{<br />
	return id;<br />
}

-----

int* workflow::getIDArray()<br />
{ <br />
	int total = numNodes; <br />
	int i = 0;<br />
	int* IDs = new int[total];<br />
	wNode* temp = first;<br />
	while (temp != NULL) {<br />
		IDs[i] = temp->getId();<br />
		if (temp->getHasLeft()) {<br />
			IDs[i+1] = temp->getLeft()->getId();<br />
			i++;<br />
		}<br />
		temp = temp->getNext();<br />
		i++;<br />
	}<br />
	return IDs;<br />
}

-----

<br />
int* wf_ids = dg_scenario::dg_workflow->getIDArray();<br />

any help would be greatly appreciated..i am new to c++ and thus am having a hard time tracing my steps and finding which line has the faulty pointer issue.

NOTE: the application has no compiler errors.

--
dg

Hans Dietrich16-Jun-07 20:33

Hans Dietrich

16-Jun-07 20:33

You've left too much out to give you any real help. What is numNodes? Exactly which line in getIDArray caused the access violation? You should run your app under the debugger, put a breakpoint on the first line in getIDArray, and step through it, looking at variables.

p.s. It's much easier to read code if you use the "pre" tags.

Best wishes,
Hans

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Re: First-chance exception ... access violation ... pointer issue

moonraker92816-Jun-07 21:48

Re: First-chance exception ... access violation ... pointer issue

16-Jun-07 21:48

numNodes is a data member in the workflow class that keeps a count of the number of nodes in the workflow.

here is the complete runtime error:

First-chance exception at 0x004fd341 in spring.exe: 0xC0000005: Access violation reading location 0xcdcdcdcd.
Unhandled exception at 0x004fd341 in spring.exe: 0xC0000005: Access violation reading location 0xcdcdcdcd.

the line it takes me to is:

int wNode::getId() 
{
	return id; <<<<----------------that one
}

is there anything else you need??

i tried putting a breakpoint in the first line of getIDArray but what do you mean "step through it"?

--
dg

Bram van Kampen18-Jun-07 13:38

Bram van Kampen

18-Jun-07 13:38

Typicaqlly Access violation reading location 0xcdcdcdcd means you read Uninitialised Data. This is how the Compiler (Debug Version) Padds Newly Allocated Data.

LateNightsInNewry

Re: First-chance exception ... access violation ... pointer issue

Stephen Hewitt17-Jun-07 12:51

Stephen Hewitt

17-Jun-07 12:51

I give the following advice about once a month (recently every few days); it often helps me track down the nastier heap errors:

Try enabling the page heap[^] for your process. Follow these steps:
1. Download and install WinDBG[^].
2. Select “Start”->“All Programs”->“Debugging Tools for Windows”->“Global Flags”.
3. Select the “Image File” tab.
4. In the “Image: (TAB to refresh)” edit control enter the name of your app then press TAB. Just the name with the extension; not the full path.
5. Tick the following:
- “Enable page heap”
- “Enable heap tail checking”
- “Enable heap free checking”
- “Enable heap parameter checking”
- “Enable heap validation on call”
- “Create user mode stack trace database”
6. Press “Apply”.
7. Debug your application. Any debugger will do but with WinDBG you have access to the stack traces of allocations via the !heap –p –a command, for example. When a heap problem is detected a breakpoint will be generated.
8. When done un-tick all the options you ticked, press “Apply” then dismiss GFlags. This step is important as if it’s skipped all applications named as entered in step 4 will run with the page heap enabled.

Note that when using the page heap your application will run much slower than normal and consume way more memory. It’s good to have a beefy machine to do such tests; and such tests should be ran regularly on all applications you develop as part of regular testing activities. If I find a part of my application that’s too slow with the page heap enabled I optimize the memory allocation in that region.

Steve

Re: First-chance exception ... access violation ... pointer issue

Bram van Kampen18-Jun-07 13:49

Bram van Kampen

18-Jun-07 13:49

Question

What is the reason for those nasty heap problems. I Still use VCPP5.00 and have had very very few of these problems. One Process was closed down recently for other reasons after 1100 days running on Win98! Total Memory Leaks: 8096 Bytes. What's Happened ?

LateNightsInNewry

drawing 2D in C++

moonraker92816-Jun-07 19:33

16-Jun-07 19:33

i am trying to draw 2D polygons and lines in C++ and i was wondering what libraries i can use. also are there any good tutorials i can refer to...

my end goal is to output a 2D square with a background color and some text inside of it...

any ideas/suggestions..? i have tried google and cant seem to find good resources..

thanks in advance.

--
dg

Cyrilix16-Jun-07 21:41

Cyrilix

16-Jun-07 21:41

You can use GDI+. I've used it to create a form with a chart control (basically inherits panel) in Managed C++, and it wasn't really that hard to pick up. You can also use GDI+ with native code though.

moonraker92816-Jun-07 22:01

16-Jun-07 22:01

nice..thanks!! this is probably a stupid question but after you download the .dll file off the ms website, where do you save it so all the classes work properly in my app??

--
dg

moonraker92816-Jun-07 22:51

16-Jun-07 22:51

I am actually having trouble using GDI+ without getting compiler errors..

i have all my header files including GdiPlus.h in: C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\Include

i have the GdiPlus.lib in: C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\Lib. i have also added GdiPlus.lib file in the additional dependencies of my project.

i have the .dll file stored in my local app directory..

when i #include GdiPlus.h, i get 107 compiler errors some of which are like the following:

1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(28) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(28) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(520) : error C2146: syntax error : missing ';' before identifier 'ObjectTypeIsValid'
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(520) : error C2433: 'BOOL' : 'inline' not permitted on data declarations
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(520) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(523) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(548) : error C2065: 'META_SETBKCOLOR' : undeclared identifier
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(548) : error C2056: illegal expression
1>C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\GdiplusEnums.h(549) : error C2065: 'META_SETBKMODE' : undeclared identifier'

.. i am completely lost. any help on fixing this and enabling me to use GDI+ in my app without any trouble will be greatly appreciated.

--
dg

Derived Class and Base Class

Cyrilix17-Jun-07 0:17

Cyrilix

17-Jun-07 0:17

Sorry, I can't really help you out with setting up the environment for using GDI+ in native C++ as I've never done it myself -- I've only used the managed version.

As for your compiler errors, error C4430 typically indicates that you're missing the definition of a certain struct/class. The line number will tell you which one in particular it does not recognize, that you're trying to use.

CLSID

Rose8116-Jun-07 16:14

Rose81

16-Jun-07 16:14

Hello

How can i change the CLSID and progid for already existing projects.Should i generate this for each project using guidgen.exe?I want to be able to load the dlls from a different target path, as a seperate plugin.is it sufficient to change the clsid alone or should progid needs to be modified as well? What will be the efficient way to do this.

Thanks

Re: CLSID

Randor 18-Jun-07 4:06

Randor

18-Jun-07 4:06

I think the only practical way to do this is generate a new CLSID and paste it into the IDL file manually. Followed by a rebuild all. I have done this in the past to seperate different builds of COM objects.

Best Wishes.
-Randor (David Delaune)

Re: CLSID

Rose8118-Jun-07 11:59

Rose81

18-Jun-07 11:59

Thanks for the reply David. Can i similarly change in the .rgs file associated with each project and do a rebuild all.The ProgID should not matter for loading dlls with same name from different target path right. Or can i manually change the last field of Project.ClassName.1 to Project.ClassName.2 in the .rgs file.I think the version independent progid can remain the same.

Thanks!

Re: CLSID

Randor 18-Jun-07 14:37

Randor

18-Jun-07 14:37

Yes, I forgot to mention that the .rgs files should also have the CLSID replaced. This is required to register the DLL and its interfaces. Technically the ProgID and the filename does not matter as long as all GUIDs have been changed. In fact; this why COM was invented (The cure for DLL Hell) although it failed miserably.

For the sake of completeness:
WinSxS (Side-by-Side) is Microsofts latest cure for DLL-Hell. http://msdn2.microsoft.com/en-us/library/aa374224.aspx[^]

Best Wishes,
Randor (David Delaune)

Re: CLSID-proxystub

Rose8124-Jun-07 11:49

Rose81

24-Jun-07 11:49

How is proxystubclsid generated?I find that in my application proxystubclsid is same as proxystubclsid32 and a default (same)value is used for all interfaces.

opengl

kayana16-Jun-07 16:13

kayana

16-Jun-07 16:13

i am a multimedia student...next year i must develop a multimedia project to get my degree...can you all help me what is the suitable and the best project that i should develop...please give idea...thanks Big Grin | :-D

kayana

Re: opengl

leckey17-Jun-07 16:53

leckey

17-Jun-07 16:53

This is a site for those who write actual code and the code does not work. Figure your own ideas on your own time.

______________________
stuff + cats = awesome

ForNow16-Jun-07 15:49

ForNow

16-Jun-07 15:49

I am new to C++ have done some mainframe programming

I have a C++ question I figure Here is the best place to post it

What is the main advantage of having base and derevied classes instead of 2 seperate declarations
e.g.

Class MyClass : public CSstring

{

.
.
.
}

As opposed to

Class MYclass;
Class CSstring;

Is it that in former I can get at CSstring protected members/Methods ????

Thankx

Cyrilix16-Jun-07 16:08

Cyrilix

16-Jun-07 16:08

There are many uses of inheritance, one of them being that you can develop interfaces. Inheritance is also a fundamental when it comes to using object-oriented design to solve problems. Depending on what kind of problems you are trying to solve and the complexity of the framework that you have to design, you may not use it much, or you may use it quite extensively.

In your example, yes, you can access protected members/methods, but that's not the reason why you'd use inheritance. If you have no need for any class hierarchy, then there might not be any benefits from using it.

ForNow16-Jun-07 16:19

ForNow

16-Jun-07 16:19

its mainly a design thing The Base Class could be the lowest level interface, Where a user is Using a Object he/She may not need to access that low a level However the Derived Class may have a need for it

I have a project I want to write and I think once I get to coding I'll get a better feel for it

Thankx

David Crow18-Jun-07 2:48

David Crow

18-Jun-07 2:48

What if you had a Car class and a Truck class? It wouldn't make much sense to have all of the common aspects duplicated between each. Instead, everything that is common to both a car object and a truck object should go in a base class (named Auto or Vehicle). Make sense? You could apply the same logic to:

          Shape
     /      |       \
Ellipse Rectangle Triangle
   |        |
Circle   Square

And:

  Animal
 /   |  \
Dog Cat Horse

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne