Re: Compiling under Win32 as Multithreaded-Non-DLL? - O. Baum - com.mysql.lists.plusplus

5 messages in com.mysql.lists.plusplusRe: Compiling under Win32 as Multithr...

From	Sent On	Attachments
O. Baum	22 Apr 2008 05:33
O. Baum	22 Apr 2008 08:50
O. Baum	29 Apr 2008 02:54
Warren Young	29 Apr 2008 04:05
Joseph Artsimovich	29 Apr 2008 06:57

Subject:	Re: Compiling under Win32 as Multithreaded-Non-DLL?
From:	O. Baum (oli...@freenet.de)
Date:	04/29/2008 02:54:58 AM
List:	com.mysql.lists.plusplus

Hi again,

in the last days I did some extensive investigations on my problem.

Let me first mention some facts about /MT and /MD and DLL creation: * It is normally no problem to create a DLL compiled with /MT. * The EXE which uses this DLL *should* be then also compiled with /MT to prevent strange effects from happening. These effects are described here <http://msdn2.microsoft.com/en-us/library/ms235460.aspx>. * A DLL interface can be designed in a way these effects do not occur.

HOWEVER, one will run into a huge linkage problem IF one compiles a DLL with /MT AND the DLL interface contains classes which are derived from C(++)-std-lib's classes (like std::string, std::ostream etc.). Exactly this is the case in MySQL++: The Query class is derived from std::ostream, which leads to linkage errors LNK2005 and LNK1169 when trying to link the MySQL++ DLL with the main program's EXE. (All links and works correctly if all is compiled with /MD.)

Could anybody help me please? I am not able to compile my main program's EXE with /MD, because I need to link MFC statically. I cannot compile MySQL++ with /MT because then the described "strange effects" (including corrupt stack, crash when calling CDateTime::str() etc.) occur.

When I link MySQL++ statically all works, but this is not allowed due to LGPL restrictions.

Thank you for help in advance!

With best regards,

Hi all,

is it possible to compile the MySQL++ library so I can use it in an application that needs to be built as "MFC in a static library" and "Multithreaded (/MT)"?

My build environment: MS VC 7.1.6030 (VS2003), WinXP, MySQL 5.0.58 commercial.

My problem: If I compile MySQL++ as "Multithreaded DLL (/MD)" it does not link with my application (getting lots of unresolved externals linker errors of STL stuff like ---8<-------------- error LNK2019: unresolved external symbol '"__declspec(dllimport) public: void __thiscall std::basic_ostream<char,struct std::char_traits<char> >::_Osfx(void)" (__imp_?_Osfx@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEXXZ)', used in function '"public: __thiscall std::basic_ostream<char,struct std::char_traits<char> >::sentry::~sentry(void)" (??1sentry@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAE@XZ)' --->8-------------- ).

If I compile MySQL++ as "Multithreaded (/MT)" it links but my application crashes when Calling the str() methods of Query and DateTime instances when leaving the current scope. You can easily verify this by compiling just the mysqlpp-Project as "/MT" and add ---8<-------------- mysqlpp::DateTime dt( 2008, 04, 22, 12, 22, 22 ); string qstr = dt.str(); cout << "test: " << dt << std::endl; --->8-------------- to simple2.cpp.

Strangely, if I compile excommon and simple2 as "Multithreaded (/MT)" it also does not link, although all should fit together in that case.

I would be very glad if anybody could shed some light on this issue(s)...

Thanks in advance,

-oli- (O. Baum)