I'm a beginner! I try to use shared MFC libraries with an old dll, but when I compile it with VC6 I obtain the error "LNK2005: _DllMain#12 already defined".
I found so many explanations, but only removing "_USRDLL" the issue disappear and the dll work. Now I'm a bit confused about the consequences of this action.
In addition, I read on MSDN that a USRDLL correspond to a regular DLL that statically links to MFC. So, when I create a new Win32 Dynamic-Link Library with VC6, why "_USRDLL" is already present if I choose in Project->Setting->Genaral "Use MFC in a shared dll" or "Not using MFC"?
Sorry for my bad english and thank you for any help!
A regular DLL with the MFC never has a DllMain.
This is covered by the CWinApp object.
Only Extension DLLs have a DllMAin. Read TN033.
_USRDLL has to be defined in this case!
Related
dllmain.cpp(16): warning C4447: 'main' signature found without threading mode
l. Consider using 'int main(Platform::Array<Platform::String^>^ args)'.
Above is a warning I got from building a Windows Store App DLL project. I didn't change anything in that default dllmain.cpp file except for including my own version of pch.
The documentation for this warning (along with many VS2012 errors/warnings) is nowhere to be found on MSDN and here is the only relevant link I can find:
http://social.msdn.microsoft.com/Forums/en-US/vssetup/thread/6daa9587-fe54-4e84-a8b9-0e5c52c2f6e8/
and the op there didn't get an answer.
If anyone knows what it means and how to fix it, it would be great!
As far as I can tell, you can safely ignore the warning. The compiler cribs when it sees a Win32-style DllMain being compiled using the /ZW flag (Consume Windows Runtime Extensions). However, the function gets called as you'd normally expect.
Alternatively, you can work around the warning by compiling dllmain.cpp without /ZW. You might need to adjust the PCH settings for this to properly work. This is the path taken by the DLL (Windows Store apps) C++/CX project template in Visual Studio.
Incidentally, the reason you do not get the warning when you're trying to build a Windows Runtime Component project (which builds everything using /ZW) is that a Windows Runtime Component doesn't declare a DllMain. This is not to say that it can't; it just picks up the dummy DllMain that the CRT defines (which basically turns off per-thread initialization and reports success).
I have a new project where I cannot use boost::format. I get a compiler error complaining that boost's override of a virtual function, ~basic_altstringbuf, lacks a "throw()". Even the most trivial attempt to use boost::format does that.
I have other projects where it works fine. I have verified that the new project uses the same include-paths for boost, and for the VC++ includes. All the projects have "Enable C++ Exceptions" set to Yes. The only explanation I can come up with is that the projects that work have some #DEFINE or some setting that disables those vile exception specs in the std:: include-files. But I have no idea what or where it might be. Any ideas?
Error 1 error C2694: 'boost::io::basic_altstringbuf::~basic_altstringbuf(void)': overriding virtual function has less restrictive exception specification than base class virtual member function 'std::basic_streambuf<_Elem,_Traits>::~basic_streambuf(void) throw()
EDIT: Corollary question: Is there a Properties-item in VS++ 2012 that will cause the std:: header files to be included without exception-specs? - short of turning off exceptions, that is?
At the request of the original owner of the green check-mark, I am submitting this summary.
The bugs are on the Microsoft side, in header-files for C++ standard library interfaces, and in the VC++ compiler when "Disable Language Extensions" is NOT set. The header files contain exception-specifications that the standard does not call for. When "language extensions" are not enabled, the compiler accepts invalid code. I have filed a bug report.
Boost could work around the problem in this specific case by adding seven characters to a nested include-file, i.e. "throw()" at line 65 in alt_sstream_impl.hpp. I filed a report with boost also, although I made it clear that the bug is not in their code. I am just suggesting a workaround.
All the tedious details are in the two reports linked above.
Check the preprocessor defines.
You might turn on and inspect verbose logging to see the exact flags that are passed to cl.exe
You could keep the preprocessed source and compare the version from the old (working) project with the new (failing) project.
My gut says, something else is being #defined/passed using -D in the old project that is not being defined in the new project, of differently (think of WINVER type macros)
See new answer posted: VC++ 2012 and Boost incompatibility - `throw()` specifications in library headers
EDIT by OP, Jive Dadson - It turned out to be /Za, which enables/disables "Microsoft language extensions." It is the contention of Visual Studio that the C++ standard requires that a program shall not compile if it has a virtual function override that is less restrictive in the "throw()" category than the function it overrides. Boost has a class that derives from basic_streambuf, and has a virtual destructor that lacks "throw()". The original destructor has that evil festoon. My new project will compile boost::format if I turn MS language extensions ON.
So the question becomes, who is wrong, and how? Is it standard-complying to put throw() on that destructor or not? Is the desired behavior (desired by me, that is) actually an "extension"? I seem to recall that MS considered some standard C++11 features to be "extensions," but I am not sure I remember correctly. Anyway, I will leave it to the boosters to decide, if they are interested. https://svn.boost.org/trac/boost/ticket/7477
I'm trying to build my application with MSVC 2010 instead of GCC. With GCC everything works fine. My app uses boost_system and boost_thread libraries.
I built boost with VC2010 in "system" layout, that means the libraries are named just libboost_system.lib (and not libboost_system_compiler_threading_version_wtf_snafu.lib)
The libs reside in C:\Boost\lib,
the Makefile specifies
LFLAGS = /NOLOGO /INCREMENTAL:NO /SUBSYSTEM:CONSOLE
LIBS = /LIBPATH:C:/Boost/lib libboost_system.lib libboost_thread.lib Ws2_32.lib
when invoking nmake it compiles, but when trying to link it quits with
LINK : fatal error LNK1104: cannot open file 'libboost_date_time-vc100-mt-1_43.lib
I mean seriously, WTF? I told it to link libboost_systen.lib and libboost_thread.lib how come it tries to link libboost_data_time and why does it assume I built the libs in "tagged" layout??
How can I stop MSVC trying to be smart and guess what I might have wanted to link?
Thanks,
Philipp
This is a feature of the Boost libs with compatible compilers for automatic linking.
(Those convoluted library names cover the myriad of threading and linking options that are available on the platform; there are good reasons to use that convention on Windows...)
More information here:
http://www.boost.org/doc/libs/1_33_1/more/getting_started.html#auto-link
I can't find a page for a more recent version, but I believe the BOOST_ALL_NO_LIB and related options are all still valid in 1.43.
Assuming you are auto-linking (i.e. you've defined BOOST_ALL_DYN_LINK or library specific equivalents).
For layout 'system' you have to define the preprocessor macro:
BOOST_AUTO_LINK_NOMANGLE
to link to the correct library names.
For layout 'tagged' you have to define the preprocessor macro:
BOOST_AUTO_LINK_TAGGED
to link to the correct library names.
I don't know if you could do this override for some libraries and keep the default for others. That would be a very cumbersome setup I'd imagine.
I have an old c++ project compiled with VC6.
I need to statically link a new library to implement a new functionality.
Unfortunately the new library define a symbol (i.e. _inflate) that is already defined in a previously linked static library.
Of course I cannot get rid of either library, and of course I have no access to the library's source code.
Is there a way to avoid the linker error (LNK2005)?
If you know that the two versions of _inflate are identical, or at least "compatible", then you can use the /FORCE:Multiple linker option to force it to ignore name clashes.
Of course, if it links to a version of that code that is "incompatible" in any way it could cause undefined behaviour.
I'm trying to test out a library that provides a VC++ example; however, I use gcc/g++ for all of my projects.
Well, the way the VC++ example accesses the library is it uses the #import directive, passing the location of the library DLL, then it does a using namespace LIBRARYNAME, and then it's able to create some undefined type (I'd assume it's defined in the DLL) and create a new instance of it with __uuidof. From then on, to call one of the library functions the example just does a createdObj->foo() and that's that.
Well... g++'s #import is different from VC++'s import (see here), so this example won't work for me.
Is there any way this can be converted to compile under g++, or am I SOL until the library developer provides me with a static library I can try out?
If you are using cygwin, then this page: http://www.cygwin.com/cygwin-ug-net/dll.html will provide you with all the help you need.
If you are using mingw, you can accomplish the same thing, but you probably won't have grep and sed, so you'll have to use some other method of doing the filtering to get your .def file.
If you were using #import in VC++ it means the DLL isn't a regular DLL, it's a COM DLL.
Since gcc doesn't have COM support, you'll just have to wait for the library author to write a non-COM version.
Maybe it could have helped you to use the OLEViewer and "View type information" to extract the basics of the IDL. Or maybe you could just use the VC++ generated .tlh and .tli files and import them into your G++ project.
I guess this answer is way too late, but right now I'm encountering similar issues myself so I just got into this thread. Hope you found the solution on time.
Regards.