C / C++ / MFC

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 4:45

I've got a code segment below that converts the block of chars read in from an RSS XML file and converts it to the unicode equivalent using a code page (the code page ID is determined beforehand by scanning for the the encoding ID in the XML).

Sometimes it works, sometimes it crashes the application. I'm using the buffer requirement returned by 'MultiByteToWideChar' to allocate the buffer required (+1 because the block of chars I'm passing does not include the 0 terminator). What's really odd is that on small strings it works fine, but on a 216 character string it crashes. If I extend the buffer allocation by 1 then it works all the time. I should not have to kludge buffer allocation to make things work.

int nSizeReq = MultiByteToWideChar(m_nCPID,0,(const char* m_pChars,nBlockLength,0,0);
TCHAR* pszConverted = new TCHAR[nSizeReq+1];
_tcsnset(pszConverted,0,nSizeReq+1);
MultiByteToWideChar(m_nCPID, 0, (const char*)m_pChars,nBlockLength, pszConverted, nSizeReq);
//up to here it always works, but the next step crashes because pszConverted has damage
//past its memory allocation
CString strConverted = pszConverted

Any ideas why this could be happening?

ps. it runs just great in debug, and if I run it in release mode whilst in visual studio it also works. Run the release by itself and *boom*

[edit]
Coded in C++ (MFC application) using Visual Studio 2008
Unicode is defined
Testing on Vista.

modified on Friday, March 13, 2009 10:51 AM

led mike13-Mar-09 5:37

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 5:37

First thing I notice is the code you posted does not check the return value of MultiByteToWideChar. Therefore your next operations are running on blind faith. This is not usually considered a Software Development Best Practice.

RichardBrock13-Mar-09 6:22

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 6:22

Yep, you make a good point, I updated the code to check the value:

int nSizeReq = MultiByteToWideChar(m_nCPID,0,(const char* m_pChars,nBlockLength,0,0);
TCHAR* pszConverted = new TCHAR[nSizeReq+1];
_tcsnset(pszConverted,0,nSizeReq+1);
int nConverted = MultiByteToWideChar(m_nCPID, 0, (const char*)m_pChars,nBlockLength, pszConverted, nSizeReq);

int nTest = wcslen(pszConverted);

the results: nConverted = 214. nSizeReq = 214, but nTest = 206. Weird.

led mike13-Mar-09 7:40

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 7:40

RichardBrock wrote:
Weird.

What are you compiling to?

Try

int nTest = _tcslen(pszConverted);

RichardBrock13-Mar-09 8:00

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 8:00

The project outputs a 32 bit Windows executable (target platforms are XP and Vista), MFC linked is static.

I tried _tcslen as you suggested, same result. I'm testing from a live RSS feed, so the news item length has changed but here's the latest output from my outputdebugstring placed just after the 2nd MultiByteToWideChar call.

'return value = 140 (wcslen is 308) nSizeReq = 140 nBlockLength = 140'

so you can see the function call returns 140, the buffer allocated was 140 and the block length read from the file is 140. But the converted string is 308 in length, obviously overruning memory allocated to it.

Do you think compiler optimization could be causing a problem? I'm compiling with 'Enable link-time code generation (/GL)'.

Btw, a previous call for the preceding news item yields:

'return value = 121 (wcslen is 121) nSizeReq = 121 nBlockLength = 121'

led mike13-Mar-09 8:41

Re: MultiByteToWideChar crashes out on longer strings

13-Mar-09 8:41

You did not answer my question, I guess I didn't make it clear but I assumed you had some knowledge about what you were doing.

led mike wrote:
What are you compiling to?

Since the subject of this discussion is character sets that's what that question is about. Are you compiling to _UNICODE or what?

You should check out the example of MultiByteToWideChar in this article[^]

Try to look for the differences in your code, there an obvious difference. Next I strongly urge you to study this subject thoroughly before you attempt your implementation. My experience is that working with conversion requires a sound understanding of this subject. I believe there are great articles here on Code Project that cover this topic well.

Akt_4_U13-Mar-09 5:39

Akt_4_U

13-Mar-09 5:39

How are you calculating this nBlockLength?

prvn

Re: MultiByteToWideChar crashes out on longer strings

RichardBrock13-Mar-09 6:26

get the font of my control and set it with an other (the face name)

13-Mar-09 6:26

I have a file open using CreateFile, I use ReadFile to locate the start and end tags in the XML file for the field, e.g. <description>.....</description> (Internet RSS news feed in Arabic). The nBlockLength indicates the number of characters extracted between > and <, the m_pChars buffer holds the actual character data.

MrKBA13-Mar-09 4:26

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 4:26

Hi,

I want to know how can i get the font of system and modify it with an other and apply it again.
the problem that the control is related to system font (ActiveX)specialy a WebBrowser.

So, how can you help me please ? Wink | ;)

Code-o-mat13-Mar-09 5:15

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:15

Try something like:

LOGFONT logFont;
my_control.GetFont()->GetLogFont(&logFont);
_tcscpy(logFont.lfFaceName, _T("the_name_of_my_favourite_font"));
my_controls_font.CreateFontIndirect(&logFont);
my_control.SetFont(&my_controls_font);

Of course, add nice error checks and such as you like.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

MrKBA13-Mar-09 5:30

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:30

Ok, but can you tell me again please what i should put in the variable my_control ? such as you know that the control is an webbrowser (activeX)?

Code-o-mat13-Mar-09 5:39

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:39

So you mean, with the question "how to set the font of my control" you actually wanted to ask "how to use the ActiveX web browser control"? Actually i have no idea, did you place the ActivX thing on your GUI using VS's resource editor? If so, you probably can add a member for it with the same.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

MrKBA13-Mar-09 5:47

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:47

Yes , i had assign an ID to this control and i understood how i put the name of my_control
but the problem exist when i do the line below :

CWindow wnd = GetDlgItem(IDC_EXPLORER);
wnd.GetFont()->GetLogFont(&logFont);

it say that there is a Error ---> 'GetLogFont' : is not a member of 'HFONT_'
so can you help me about this and should i make a casting and how?

Thank you

Code-o-mat13-Mar-09 5:57

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:57

Ah...CWindow...that calls for a change of plans...try this instead:

LOGFONT logFont;
GetObject(wnd.GetFont(), sizeof(LOGFONT), &logFont);
...change the logfont as needed...
HFONT NewFont = CreateFontIndirect(&logFont);
wnd.SetFont(NewFont, TRUE);

Don't forget to DeleteObject NewFont once you are not using it anymore. Does this work?

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

MrKBA13-Mar-09 6:29

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 6:29

Sorry Code-o-mat but the problem exist always and that make me crazy Confused | :confused:

led mike13-Mar-09 5:41

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:41

Ah, you allowed yourself to be fooled into thinking the question was about fonts when actually it was about working with a Web Browser control. Now what?

MrKBA13-Mar-09 5:51

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:51

No, i had trying much time with this but the problem is still until this control is related to OS.So for that reason i would know how can i modify the font of system in my source code.

Code-o-mat13-Mar-09 5:52

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 5:52

I let shame eat up my soul, get addicted to antidepressants and jump from the north bridge into the datastreams. Smile | :)

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

MrKBA13-Mar-09 6:17

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 6:17

So, there is no idea !!!! Sigh | :sigh:

thanks for all

Code-o-mat13-Mar-09 6:26

Re: get the font of my control and set it with an other (the face name)

13-Mar-09 6:26

So this[^] failed too?

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

MrKBA13-Mar-09 6:33

Error C1900 with static library

13-Mar-09 6:33

yes, it has always the font of system

Trollslayer13-Mar-09 4:19

Trollslayer

13-Mar-09 4:19

I am trying to use a static library that, although it is meant to be for VC8 produces the following error when build the suppliers sample application:

Linking...<br />
fatal error C1900: Il mismatch between 'P1' version '20060201' and 'P2' version '20050411'<br />
LINK : fatal error LNK1257: code generation failed

I don't have the source for this library, any suggestions?

Visit http://www.notreadytogiveup.com/[^] and do something special today.

Re: Error C1900 with static library

led mike13-Mar-09 4:30