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[Jeremy Clarkson Voice] Some say that it's impossible for the stig Carlo to hack his way out of wet socks. [/Jeremy Clarkson Voice]
It was ever thus, the Neophiles will always rush out and get 'The Latest Thing' at a high price and with all the inherent faults - Dalek Dave.
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None of these approaches are inherently more 'secure' than any other.
WM_APP is a little better than WM_USER, because a number of the builtin Windows controls use messages in the WM_USER range.
Both WM_USER and WM_APP messages are easier to detect using Windows Spy++, since they have fixed values.
RegisterWindowsMessage is slightly more difficult to detect, since the value can change each time the message is created (the first time it is called with a given string, a new value is created; further calls with that string get the same value). A determined hack could look for calls to RegisterWindowsMessage and duplicate your string.
One option would be to use a randomly-generated string (such as a GUID) that your application and your DLL's could agree on. A simpler alternative would be to generate a random number between WM_APP and 0xBFFF and pass that to your DLL's via a conventional function call at initialization time.
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After reading Joseph M. Newcomer's article (http://www.flounder.com/messages.htm), he is favoring in using RegisterWindowsMessage
However, there are some concern that, RegisterWindowsMessage may lead to resource exhaustion. http://stackoverflow.com/questions/1192204/can-abusing-registerwindowmessage-lead-to-resource-exhaustion
My situation is, I have a EXE with multiple DLLs. Each DLLs doesn't aware of each other DLL. Hence, the situation might happen if I am using WM_APP (Joseph M. Newcomer mark WM_USER as obsolute)
DLL_A.dll is sending DDL_A_REFRESH_MY_VIEW_MSG (WM_APP + 100)
DLL_B.dll is sending DDL_B_REFRESH_MY_VIEW_MSG (WM_APP + 100)
Does this mean, RegisterWindowsMessage will be the best choice, even my communication only tend to within a single process?
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You might try using something like this:
int WM_DLL_A_REFRESH = RegisterWindowsMessage("DLL_A:Refresh");
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I am a newbie to C++ and am trying to pass an array to a function and then display the contents of this array through the function. The array is populated through a different function though both functions reside within the same class. I am struggling to figure out how to execute the function object to execute the display function. Listed below are all of the code components:
//=============================================
Monop.h
class PurchaseProperty
{
public:
void PropInit(void);
char Display();
char DisplayProp(char [],int);
private:
};
//=============================================
MonopFunct.cpp
#include <iostream>
#include "Monop.h"
using namespace std;
using std::cout;
void PurchaseProperty::PropInit()
{
char *PropNameArray[] = {"Mediterranean Avenue","Baltic Avenue","Oriental Avenue","Vermont Avenue","Connecticut Avenue","St. Charles Place","States Avenue",
"Virginia Avenue","St. James Place","Tennessee Avenue","New York Avenue","Kentucky Avenue","Indiana Avenue","Illinois Avenue",
"Atlantic Avenue","Ventnor Avenue","Marvin Gardens","Pacific Avenue","North Carolina Avenue","Pennsylvania Avenue","Park Place",
"Boardwalk"};
float PropCostArray[] = {60,60,100,100,120,140,140,160,180,180,200,220,220,240,260,260,280,300,300,320,350,400};
float PropRentArray[] = {2,4,6,6,8,10,10,12,14,14,16,18,18,20,22,22,22,26,26,28,35,50};
float PropRent1Array[] = {10,20,30,30,40,50,50,60,70,70,80,90,90,100,110,110,120,130,130,150,175,200};
float PropRent2Array[] = {30,60,90,90,100,150,150,180,200,200,220,250,250,300,330,330,360,390,390,450,500,600};
float PropRent3Array[] = {90,180,270,270,300,450,450,500,550,550,600,700,700,750,800,800,850,900,900,1000,1100,1400};
float PropRent4Array[] = {160,320,400,400,450,625,625,700,750,750,800,875,875,925,975,975,1025,1100,1100,1200,1300,1700};
float PropHotelRentArray[] = {250,450,550,550,600,750,750,900,950,950,1000,1050,1050,1100,1150,1150,1200,1275,1275,1400,1500,2000 };
float PropHouseCostArray[] = {50,50,50,50,50,100,100,100,100,100,100,150,150,150,150,150,150,200,200,200,200,200};
float PropHotelCostArray[] = {50,50,50,50,50,100,100,100,100,100,100,150,150,150,150,150,150,200,200,200,200,200};
};
char PurchaseProperty::Display()
{
int cnt;
for(cnt = 0; cnt < 22; cnt++)
{
cout << "Program is Working";
}
return 0;
}
char PurchaseProperty::DisplayProp(char PropNameArray[], int)
{
int cnt;
for(cnt = 0; cnt < 22; cnt++)
{
cout << PropNameArray[cnt];
}
return 0;
}
//=============================================
Main.cpp
#include <iostream>
#include "Monop.h"
using std::cout;
using std::cin;
using std::endl;
char DisplayProp(char PropNameArray[],int);
int main()
{
PurchaseProperty object;
object.PropInit();
object.DisplayProp(PropNameArray,22);
return 0;
}
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There are really a lot of errors in this code:
1) In the init function, you initialiaze a couple of arrays but these arrays are local to the init function, so you won't be able to access them. Which means that the code in the init function is useless. It is better to make these arrays members of your class.
2) Why do you declare a global DisplayProp function (in the main.cpp file) ? This function is a member of your PurchaseProperty class, so here you are simply declaring a new function that won't be used at all (and that doesn't even have a definition).
3) In your main function, you are calling DisplayProp and passing PropNameArray as argument. This variable doesn't exist anywhere, you need to actually pass an array that exists. What do you want to print there ? One of the arrays that was initialized in the Init method of your class ?
4) What is Display supposed to do ? What is the different between Display and DisplayProp ?
I really suggest that you start from a good book because it seems you lack some fundamental principles and without understanding them really well, you will have a lot of trouble writing any software.
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Cedric,
Thank you for your comments. I have been self studying C++ How to Program as well as C Primer Plus. This is my first program. It is not copied from any source as I am trying to learn how to apply the principles.
As for my posting to clarify the problem I am having is the following (I should have been more clear in my initial posting):
I am attempting to call DisplayProp function which is a member of the PurchaseProperty class. I am making this call in the program Main. I though am having problems getting the program to recognize "PropNameArray". The following is the error message I am getting in Visual Studio 2008:
1>c:\users\mike certini\documents\visual studio 2008\projects\monopoly3\monopoly3\main.cpp(15) : error C2065: 'PropNameArray' : undeclared identifier
1>Build log was saved at "file://c:\Users\Mike Certini\Documents\Visual Studio 2008\Projects\Monopoly3\Monopoly3\Debug\BuildLog.htm"
--------------------------------------------------------------------------------
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As Cedric already said, you really should get a good book, there's just too many problems with your code way beyond the syntactical issues your compiler complains about.
The latter is due to your apparent misunderstanding on the scope of variables in C/C++. If you declare a variable, this variable is only known within the scope it is declared in. In most cases this scope is between the previous opening '{' and the corresponding closing '}'. There are basically two exceptions: If you define a variable within the definition of a class (or a struct), then every function that is also defined as a member of that class has access to it. The other exception is when you declare a variable outside a function or class (or struct), which makes it a global variable. Global variables may be accessed anywhere, provided it's declaration comes prior to the location where it's defined. Check your C/C++ book of choice for further explanations on how to declare and access global variables. However, it is a good practice to keep the number of global variables to a minimum.
The compiler states that PropNameArray is an undeclared identifier because within the scope of the main function, the variable PropNameArray is not known. It is only known within the function PropInit(), where this variable was declared.
Note that all variables will be automatically destroyed when program execution leaves the scope they are declared in. In other words, when you execute the function PropNameInit(), the system will first create all these variables, then initialize them, and, when it leaves the function, immediately destroy them again. As has been pointed out in another response, the function PropInit() currently does nothing! You have three options:
1. Make the variables global (which is bad design).
2. Create the variables outside of the function (i. e. in main) and pass them as arguments to the function PropInit (which is impractical)
3. Declare these variables as attributes of the class
Hope this helps to get you started, but like stated before, do yourself a favor and get a book.
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You are also missing the element count argument in DisplayProp
char PurchaseProperty::DisplayProp(char PropNameArray[], int count)
{
int index;
for(index = 0; index < count; index++)
{
cout << PropNameArray[index];
}
return 0;
}
No point supplying it if you don't use it.
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Hi all,
I am writing an app using C++, Visual Studio 2008 and Qt. I have been working on a certain section of code, and i have it working now without any problems. That is in debug mode. When i compiled it in release mode the other day, the app crashed (access violation) when i performed a certain action (selecting an item from a combo box). This did not happen in debug mode, and it happens consistently whenever i switch back to compiling in release.
My app is similar to Spy++ or Winspector and it uses a hook to monitor other window's messages. It does this by injecting a DLL in other processes. When i first tried to debug the crash in VS, the stack trace included the hook procedure and it even showed me the code (which is strangle because the DLL should have been built without symbols too). It was indicating that the crash was around the call to CallNextHookEx.
But i don't think it has anything to do with that because when i commented out the hook code, the crash still happened.
I suspect it is due to memory corruption, but i don't know how to be sure. Basically, i am asking for any tips on how to debug such a situation. I cannot step through the code as there are no symbols in release mode, and the DLLs in other processes only makes debugging harder.
Since i have no idea what could be causing the crash, i will not post any code. However, i will upload the entire source (to my SourceForge site) and post a link to it so that you can browse though it if you like.
If it helps, the assembly where the crash happened is:
004320EE mov edx,dword ptr [eax+ecx*4+14h]
[ Window Detective] - Windows UI spy utility
modified on Thursday, December 9, 2010 5:50 PM
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1.) you can compile a release with the option 'generate debug info' too.
2.) insert beeps or log-infos to localize the buggy code position.
3.) initialize all memory allocated by zero also static and local member.
4.) enshure you don't write beyond allocated memory.
5.) the debug version: checks memory (allocating more than neccessary and fill them with special values). also debug: checks the stack integrity.
6.) use the same compiler/linker options for release same as debug.
7.) turn on multithreading option.
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you could tell the linker to produce a link map, then use that to identify which function contains 004320EE mov edx,dword ptr [eax+ecx*4+14h]
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How would i do that
By the way, it is ecx that contains a rather large number, which is causing the expression to access invalid memory. So i imagine that ecx should normally contain a valid value.
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based on the virtual address.
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Sorry, i still don't know what you are talking about. You seem to be saying that there is a way to find the function which that line of code is in. While i understand that it may technically be possible, i have no idea how to do it.
btw, thanks to everyone else who replied.
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research this[^]
XTAL256 wrote: thanks to everyone else
No thanks then.
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Well, i was going to thank you once you clarified your previous post. But since you gave me the lmgtfy response, i don't think i will . Just kidding.
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Please read this: Surviving the release version[^]
It was ever thus, the Neophiles will always rush out and get 'The Latest Thing' at a high price and with all the inherent faults - Dalek Dave.
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fyi, i found the problem. I stupidly forgot to return a value from a function. I only just picked it up then when the compiler told me that "not all control paths return a value". I guess i missed that warning previously.
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I have seen the term Fixed_32 for a data item with MSB = 1 and LSB = 1/2**31 ;
Max = 1.0 and Min = -1.0 with units of semicircles (used for Latitude and Longitude)
I did think this was a float to the IEEE-754 Floating-Point Representation.
However the 3rd party that is reading some data via a message structure cannot see the same value.
I mistaken the term Fixed_32 as a standard float but it is a 32 bit int in the message.
The scalling is:-
#define BEARING_SCALING 4.65661287307739E-10
typedef struct ReceiveMessage
{
unsigned int msgNumber;
int msgPosLat;
int msgPosLong;
unsigned int msgQuality;
}positionData
#define BEARING_SCALING 4.65661287307739E-10 However I get a crash when I try to load the value (the Latitude was declared as a double and I tried to cast to the int and vice versa.
Code:
double lat = 55.55;
positionData.msgPosLat = (int)(lat/(BEARING_SCALING * 180));
lat = (double)( positionData.msgPosLat) * BEARING_SCALING * 180;
What is going wrong please, is it the oder of casting or do I need to use fix point stuff?
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I think it works like this:
the latitude in degrees ranges from -90 to +90 (and not -180 to +180).
the encoding used is 32-bit fixed integers with an implied scale factor, so the full range [-90,+90] gets mapped onto the full integer range.
So you want +90 represented by the largest positive 32-bit integer (which equals 2^31 minus one, or 0x7FFFFFFF), hence:
int fixed32(double lat) {
lat=lat/90.;
lat=lat*0x7FFFFFFF;
return (int)lat;
}
Notes:
1. this code will never return the minimum value (0x80000000). For -90 it results in 0x80000001 which is a consequence
of [-90,+90] being symmetric around zero, whereas the integer range [0x80000000, 0x7FFFFFFF] isn't.
2. I tend to avoid magic constants, such as the 4.65661287307739E-10 you had. I prefer to write them in a way that reveals what they stand for. Your value stems from 1.0/0x7FFFFFFF
3. I doubt the code you have shown would crash at all.
lat/(BEARING_SCALING * 180) will not exceed the acceptable range for integers (and your formula being wrong by a factor of 2 IMO only reassures this).
(positionData.msgPosLat) * BEARING_SCALING * 180) may incur an integer overflow (again due to the factor of 2), but normally those get swallowed.
So I expect if anything bombs, it must be the code that follows after you used these formulas, mainly the latitude going all the way up to +180.
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Thanks Luc, the Longitude (-180 to +180) has the same scaling.
I can get the code running OK on Windwos but when ported to Unix (using a Gnu complier) the program bombs out.
Debuggin a bit limited hence the use of Windows for the development.
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Andy202 wrote: the Longitude (-180 to +180) has the same scaling.
not sure what you are saying here. the longitude range has to cover 360 degrees (either -180 to +180 or 0 to +360), so it could be latitude uses the same scale factor, but then your opening statement (about MIN and MAX) isn't accurate for latitude.
OTOH if the scale factor is different for lat and lon, that would justify why the 180 (or 360) isn't incorporated in the magic constant.
Andy202 wrote: when ported to Unix (using a Gnu complier) the program bombs out.
A different compiler may generate different code, e.g. it could emit code that does check for overflows at run-time.
[ADDED] So far you have not specified where in the code it crashes. [/ADDED]
I can only suggest you:
1. include some logging statements so you can watch the numbers till the program crashes.
2. perform some unit tests (a simple loop over the range of interest should be easily implemented).
Taken together, that will clarify what goes on.
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normally c-compilers cast from left to right (implicit). if yours don't - cast yourself (explicit):
positionData.msgPosLat = (int)(lat/(BEARING_SCALING * 180.0));
// (int)(double/(double*double))
AND
lat = ( (double)positionData.msgPosLat * (BEARING_SCALING * 180.0));
// (double*(double*double))
// hint: don't define twice (BEARING_SCALING)
have a nice day.
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hi guys,,,
i'm a newbie in MFC so i'm need your advice to complete final project about identification signature. in this time i have problem about how to save image from picture box in MFC. this is my code used in MFC. this code not save image from picturebox. what's wrong with my code???
void SaveBitmapToFile( BYTE* pBitmapBits, LONG lWidth, LONG lHeight,WORD wBitsPerPixel, LPCTSTR lpszFileName );
void CSaveimageDlg::OnSave()
{
// TODO: Add your control notification handler code here
CDC *pDC = m_pic1.GetDC();
CDC dcMem1;
CRect rect;
m_pic1.GetClientRect(rect);
HDC hdc;
HBITMAP hBitmap = NULL;
BITMAP bm;
CBitmap Bitmap;
m_pic1.SetBitmap(Bitmap);
Bitmap.CreateBitmap(200 ,200,1,24,NULL);
m_bmpBitmap.GetBitmap(&bm);
//Bitmap.GetBitmap(&bm);
Bitmap.GetObject( sizeof( BITMAP ), &bm );
unsigned char *pData = new unsigned char [bm.bmHeight*bm.bmWidthBytes];
SaveBitmapToFile(pData,bm.bmHeight,bm.bmWidth,24,(LPCTSTR)_T("a.bmp"));
delete []pData;
}
void CSaveimageDlg::SaveBitmapToFile(BYTE *pBitmapBits, LONG lWidth, LONG lHeight, WORD wBitsPerPixel, LPCTSTR lpszFileName)
{
BITMAPINFOHEADER bmpInfoHeader = {0};
bmpInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
bmpInfoHeader.biBitCount = wBitsPerPixel;
bmpInfoHeader.biClrImportant = 0;
bmpInfoHeader.biClrUsed = 0;
bmpInfoHeader.biCompression = BI_RGB;
bmpInfoHeader.biHeight = lHeight;
bmpInfoHeader.biWidth = lWidth;
bmpInfoHeader.biPlanes = 1;
bmpInfoHeader.biSizeImage = lWidth* lHeight * (wBitsPerPixel/8);
BITMAPFILEHEADER bfh = {0};
bfh.bfType=0x4D42;
bfh.bfType = 'B'+('M' << 8);
bfh.bfOffBits = sizeof(BITMAPINFOHEADER) + sizeof(BITMAPFILEHEADER);
bfh.bfSize = bfh.bfOffBits + bmpInfoHeader.biSizeImage;
HANDLE hFile = CreateFile( lpszFileName,GENERIC_WRITE, 0,NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,NULL);
if( !hFile ) // return if error opening file
{
return;
}
DWORD dwWritten = 0;
WriteFile( hFile, &bfh, sizeof(bfh), &dwWritten , NULL );
WriteFile( hFile, &bmpInfoHeader, sizeof(bmpInfoHeader), &dwWritten, NULL );
WriteFile( hFile, pBitmapBits, bmpInfoHeader.biSizeImage, &dwWritten, NULL );
CloseHandle( hFile );
}
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