C / C++ / MFC Discussion Boards

ganralf18-Oct-08 1:54

18-Oct-08 1:54

Hello together,

I've tried to return a string back from a C++ dll function within VB and it is working fine, but if I try to use the same function in a C++ project it returns garbage !

does anyone know what I have to do different ? as I want to use the function in C++ as well as in VB is there a way to implement the function to fit for both languages ?

my C++ dll function:

BSTR __stdcall ReturnString2Vb(void)
{
char* str = "This is a test string...";

return SysAllocStringByteLen(str, strlen(str));
}

thanks a lot in advance for any help !
ganralf

Re: String Conversion C++ <--> VB

CPallini18-Oct-08 2:46

CPallini

18-Oct-08 2:46

Possibly it doesn't return garbage, it returns a BSTR. You may, for instance, use _bstr_t wrapper class to handle it in your C++ application.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: String Conversion C++ <--> VB

ganralf18-Oct-08 3:22

ganralf

18-Oct-08 3:22

Hi Pallini,

thanks for your quick answer !!!

do you mean I have to replace BSTR by _bstr_t ? I tried it in the following way but now I get a compile error that tells me that the _bstr_t data type is not defined. Which header do I have to include in my C++ project ?

_bstr_t ReturnString2Vb(void)
{
char* str = "This is a test string...";

return SysAllocStringByteLen(str, strlen(str));
}

would be great if you could report me an example Smile | :)

maybe important: the dll I created is a win32 dll not a MFC or similar

thanks in advance for your help !
ganralf

Re: String Conversion C++ <--> VB

CPallini18-Oct-08 3:41

CPallini

18-Oct-08 3:41

ganralf wrote:
do you mean I have to replace BSTR by _bstr_t ?

Nope.

In you client C++ application you may use _bstr_t as wrapper for the BSTR return value. You know, BSTR stands for OLECHAR *, i.e. like a wide char string, you may also handle directly it in you client app.

With VS6 compiler you need to include comdef.h to use _bstr_t class.

Re: String Conversion C++ <--> VB

ganralf18-Oct-08 3:58

ganralf

18-Oct-08 3:58

ok, thanks Pallini ! it now seems to compile and link but the result is the same Frown | :(

dll function
BSTR ReturnString2Vb(void)
{
char* str = "This is a test string...";

return SysAllocStringByteLen(str, strlen(str));
}

C++ application code
int _tmain(int argc, _TCHAR* argv[])
{
_bstr_t returned_string;

returned_string = ReturnString2Vb();

return 0;
}

as I am new to C++ and if it would be no great effort for you I think it would be helpfull if you could change the above mentioned code so that it will work.

thanks in advance !
ganralf

Re: String Conversion C++ <--> VB [modified]

CPallini18-Oct-08 4:07

CPallini

18-Oct-08 4:07

What does the following C++ application ouputs

int _tmain(int argc, _TCHAR* argv[])
{
BSTR returned_string;

returned_string = ReturnString2Vb();

wprintf( L"%s\n", returned_string);

printf("%s\n", (const char *) returned_string);

return 0;
}

modified on Saturday, October 18, 2008 9:22 AM

Re: String Conversion C++ <--> VB

ganralf18-Oct-08 4:12

ganralf

18-Oct-08 4:12

well it outputs "????????????" in the console window Smile | :)

but not the string !

thanks !
ganralf

Re: String Conversion C++ <--> VB

CPallini18-Oct-08 4:23

CPallini

18-Oct-08 4:23

Well, I'm very sorry I misread your SysAllocStringByteLen call (as SysAllocString) Blush | :O

. I've fixed my previous reply, please have a look at.
Smile | :)

Re: String Conversion C++ <--> VB

ganralf18-Oct-08 4:30

ganralf

18-Oct-08 4:30

thanks Pallini,

that's it now it works ! I have changed the application code as follows:

BSTR ReturnString2Vb(void)
{
char* str = "This is a test string...";

return SysAllocStringByteLen(str, strlen(str));
}

int _tmain(int argc, _TCHAR* argv[])
{
char* returned_string;

returned_string = (char *)ReturnString2Vb();

return 0;
}

again thanks for your help !
ganralf

Re: String Conversion C++ <--> VB

CPallini18-Oct-08 4:38

CPallini

18-Oct-08 4:38

You're welcome.
BTW don't forget to call

SysFreeString(returned_string);

when you no loger need it.
Smile | :)

Re: String Conversion C++ <--> VB

Michael Dunn18-Oct-08 18:16

Michael Dunn

18-Oct-08 18:16

ganralf wrote:
f I try to use the same function in a C++ project it returns garbage !

How are you determining that it returns garbage?

From the SysAllocStringByteLen() docs:

Takes an ANSI string as input, and returns a BSTR that contains an ANSI string. Does not perform any ANSI-to-Unicode translation.

It's a safe guess that code that takes a BSTR expects the string to be in UTF-16. Use SysAllocString() instead.

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! CP SearchBar v3.0 | C++ Forum FAQ

I work for Keyser Söze

Re: String Conversion C++ <--> VB [modified]

ganralf19-Oct-08 0:44

ganralf

19-Oct-08 0:44

Hi Michael,

thanks for your reply !

I tried SysAllocString and it works fine within a C++ project but if I try to return the string in Excel VBA it returns "T h i s i s a t e s t s t r i n g . " (every sign in the string is separated by a sign that cannot be displayed) and in VB it returns "T"

C++ dll function code

BSTR __stdcall ReturnString2Vb(void)
{
	return SysAllocString(L"This is a test string.");
}

VB code

Private Declare Function ReturnString2Vb Lib "C:\testdll.dll" () As String

Function ReturnString() as string
	Dim returned_string As String
	
	returned_string = ReturnString2Vb()
end function

what am I doing wrong ? when I am using SysAllocStringByteLen all is working fine !

thanks for your help !
ganralf

modified on Sunday, October 19, 2008 7:58 AM

Accessing Bits of Shared Memory

Andy20218-Oct-08 1:52

Andy202

18-Oct-08 1:52

I have a section of shared memory divided into 4 areas, but I would like to use memcpy() to update each section without affecting the other section.

I have a pointer memPtr;

int *memPtr;

Can I just use:-

memscpy(memPtr, sizeof(section[0]), section[0]);

and then 

memcpy(memPtr + sizeof(section[0]), section[1]);

i.e. the total ares is
MyStruct section[4]; and would like to update section[0] and section [1] as required

Thanks,

Andy.

Static linking not working

scorpiodx18-Oct-08 1:27

scorpiodx

18-Oct-08 1:27

I wrote a small "Hello World" program that compiles and runs well on the machine I compiled it on (running Vista). The .exe file didn't run on a different XP machine however. I learned about vcredist_x86, but I wanted my program to run on just copying it without having to "prepare" the target machine. I decided to go for static compilation since the program I am working on (not the "Hello world", btw) is small and simple enough, and doesn't need the latest and greatest lib updates.

When I change the compiler code generation runtime library option to /MT and try to build, I get a bunch of errors -

>Linking...
1>hello.obj : error LNK2005: "public: static unsigned int __cdecl std::char_traits<char>::length(char const *)" (?length@?$char_traits@D@std@@SAIPBD@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: static bool __cdecl std::char_traits<char>::eq_int_type(int const &,int const &)" (?eq_int_type@?$char_traits@D@std@@SA_NABH0@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: static int __cdecl std::char_traits<char>::eof(void)" (?eof@?$char_traits@D@std@@SAHXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: int __thiscall std::ios_base::flags(void)const " (?flags@ios_base@std@@QBEHXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: int __thiscall std::ios_base::width(void)const " (?width@ios_base@std@@QBEHXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: int __thiscall std::ios_base::width(int)" (?width@ios_base@std@@QAEHH@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: void __thiscall std::basic_ios<char,struct> >::setstate(int,bool)" (?setstate@?$basic_ios@DU?$char_traits@D@std@@@std@@QAEXH_N@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: class std::basic_streambuf<char,struct> > * __thiscall std::basic_ios<char,struct> >::rdbuf(void)const " (?rdbuf@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_streambuf@DU?$char_traits@D@std@@@2@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: int __thiscall std::basic_streambuf<char,struct> >::sputc(char)" (?sputc@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHD@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: bool __thiscall std::ios_base::good(void)const " (?good@ios_base@std@@QBE_NXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: class std::basic_ostream<char,struct> > & __thiscall std::basic_ostream<char,struct> >::flush(void)" (?flush@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEAAV12@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: void __thiscall std::basic_ostream<char,struct> >::_Osfx(void)" (?_Osfx@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: class std::basic_ostream<char,struct> > * __thiscall std::basic_ios<char,struct> >::tie(void)const " (?tie@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_ostream@DU?$char_traits@D@std@@@2@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: void __thiscall std::basic_streambuf<char,struct> >::_Lock(void)" (?_Lock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: void __thiscall std::basic_streambuf<char,struct> >::_Unlock(void)" (?_Unlock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: char __thiscall std::basic_ios<char,struct> >::fill(void)const " (?fill@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEDXZ) already defined in msvcprtd.lib(MSVCP90D.dll)
1>hello.obj : error LNK2005: "public: int __thiscall std::basic_streambuf<char,struct> >::sputn(char const *,int)" (?sputn@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHPBDH@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
1>LINK : warning LNK4098: defaultlib 'LIBCMT' conflicts with use of other libs; use /NODEFAULTLIB:library
1>libcpmtd.lib(cout.obj) : error LNK2019: unresolved external symbol __CrtDbgReportW referenced in function "public: char const & __thiscall std::_String_const_iterator<char,struct>,class std::allocator<char> >::operator*(void)const " (??D?$_String_const_iterator@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@QBEABDXZ)
1>libcpmtd.lib(stdthrow.obj) : error LNK2001: unresolved external symbol __CrtDbgReportW
1>libcpmtd.lib(xdebug.obj) : error LNK2019: unresolved external symbol __malloc_dbg referenced in function "void * __cdecl operator new(unsigned int,struct std::_DebugHeapTag_t const &,char *,int)" (??2@YAPAXIABU_DebugHeapTag_t@std@@PADH@Z)
1>libcpmtd.lib(xdebug.obj) : error LNK2019: unresolved external symbol __free_dbg referenced in function "void __cdecl operator delete(void *,struct std::_DebugHeapTag_t const &,char *,int)" (??3@YAXPAXABU_DebugHeapTag_t@std@@PADH@Z)
1>libcpmtd.lib(_tolower.obj) : error LNK2019: unresolved external symbol __calloc_dbg referenced in function __Getctype
1>C:\Users\Shankar\Documents\Visual Studio 2005\Projects\hello\Debug\hello.exe : fatal error LNK1120: 4 unresolved externals
1>Build log was saved at "file://c:\Users\Shankar\Documents\Visual Studio 2005\Projects\hello\hello\Debug\BuildLog.htm"
1>hello - 23 error(s), 2 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

All this for a small "Hello World" program that uses only cout.

I tried building it with Visual Studio 2005 as well as Visual C++ 2008 Express and I get the same errors.

Can anyone let me know what I am supposed to do? Thanks.

Shankar

Re: Static linking not working

scorpiodx18-Oct-08 7:45

scorpiodx

18-Oct-08 7:45

ok, after cleaning up the build, I got unresolved external symbol errors for __CrtDbgReportW, symbol __malloc_dbg, symbol __free_dbg, symbol __calloc_dbg. Are there any libraries I need to include manually?

Also I get a warning message -
LINK : warning LNK4098: defaultlib 'LIBCMT' conflicts with use of other libs; use /NODEFAULTLIB:library

but when I do that, I get too many unresolved symbol errors.

Thanks.

Shankar

In vc6 debugger, edit and continue doesn't work

sashoalm18-Oct-08 1:15

sashoalm

18-Oct-08 1:15

When I try to make changes to my code while debugging and recompile, I get this error:

Compiling...
'~vcecho!' is not recognized as an internal or external command,
operable program or batch file.
Error executing ~vcecho!

This doesn't error happens only in one particular project. On other projects, I have no problems using edit and continue. I really like being able to fix code while I'm debugging, but on this project I can't.

There is sufficient light for those who desire to see, and there is sufficient darkness for those of a contrary disposition.
Blaise Pascal

buttons in VC++2005

RNarayan18-Oct-08 1:04

RNarayan

18-Oct-08 1:04

i have two buttons in a dialog box. i could not take the control from one button to another using keyboard. it's working fine with mouse Lbutton click.
could any one come up with the reason, please.

Re: buttons in VC++2005

santhoshv8418-Oct-08 1:44

santhoshv84

18-Oct-08 1:44

Hi,

You better use Tab key.
Set the Tab order using Ctrl+D in the Dialog resource.

The price of anything is the amount of life you exchange for it.

Thanks and Regards.
SANTHOSH V

Re: buttons in VC++2005

Hamid_RT18-Oct-08 10:14

Hamid_RT

18-Oct-08 10:14

Did you set tab for your controls on the dialog?

How to store bmp using URLDownloadToFile from a URL ?

Rahul Vaishnav18-Oct-08 0:31

Rahul Vaishnav

18-Oct-08 0:31

Hi all,

I want to store bmp from urls by using URLDownloadToFile..

for example I want to store urlicon of www.yahoo.com by using http://www.google.com/s2/favicons?domain=www.yahoo.com
This url gives me the Yahoo icon.

Now I want to store this so I have used URLDownloadToFile, and It get stored also .
but by using LoadImage, I couldn't load this stored image.

Please suggest me solution or some other way of downloading fevicons of urls.

Thanks in advance.
Frown | :(

Re: How to store bmp using URLDownloadToFile from a URL ?

Hamid_RT18-Oct-08 10:14

Hamid_RT

18-Oct-08 10:14

I dont know you asked this question previous or no but you must be extract controls on the web page and on the codeproject we have a simple for it.

Re: How to store bmp using URLDownloadToFile from a URL ?

Michael Dunn18-Oct-08 18:21

Michael Dunn

18-Oct-08 18:21

What error is LoadImage() returning?

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! CP SearchBar v3.0 | C++ Forum FAQ

I work for Keyser Söze

Re: How to store bmp using URLDownloadToFile from a URL ?

Rahul Vaishnav21-Oct-08 19:30

Rahul Vaishnav

21-Oct-08 19:30

Thanks for reply..

I have resolved the problem.

Sorry for delay in reply..

[Message Deleted]

AnayKulkarni17-Oct-08 23:53

AnayKulkarni

17-Oct-08 23:53

[Message Deleted]

Re: How to remove maximize button and its box from application's main window in MDI application?

santhoshv8418-Oct-08 1:35

santhoshv84

18-Oct-08 1:35

Hi,

There is no way to make the maximize box invisible if you have minimize box.

If you dont want the minimize box also. Then use

cs.style &= ~WS_MAXIMIZEBOX;
cs.style &= ~WS_MINIMIZEBOX;

Now only you will get window without Maximize box and Minimize box.

The price of anything is the amount of life you exchange for it.

Thanks and Regards.
SANTHOSH V

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