Building DLL in Visual Studio with Static Linking to QT

koahnig · 20 Jun 2017, 08:17

What is about this toLocal8Bit? This is in QString. Do you mean QByteArray?
I do not know the syntax of VC compilers.

kshegunov · 20 Jun 2017, 08:37

?toLocal8Bit@Qstring@ is the (qualified) symbol name, Qstring::toLocal8Bit in this case.
@ is the end of symbol name (a separator).
QEGBA is the methods characteristic - CV-qualifier, access (public/private/protected), calling convention etc.
?AVQByteArray@ is the qualified name of the return type - class QByteArray.
@ is the end of section (a separator).
XZ - basically means "no method parameters".

So the above (if I haven't made a mistake) should be:

public: QByteArray __thiscall Qstring::toLocal8Bit() const;

Now, see that the class is wrong, there's no Qstring in Qt, the name should be capitalized.

koahnig · 20 Jun 2017, 08:39

@kshegunov

Sorry, I did not catch the lower case 's'.

However, when it is a typing error in user's code, it shall be caught by the compiler or there is also the same typing error in include file. All very strange.

kshegunov · wrote on 20 Jun 2017, 08:39

@koahnig said in Building DLL in Visual Studio with Static Linking to QT:

when it is a typing error in user's code, it shall be caught by the compiler or there is also the same typing error in include file.

Yes, my point exactly!

All very strange.

Indeed, something's fishy here.

mlathrop · 21 Jun 2017, 19:08

@koahnig
I am using 2015 across the board so I don't think that is the issue... Interestingly, things don't work when I build dynamically and link against the QT libraries either. The capitalization error was a typo when I re-typed the error message (it is shown on a pop-up window that I couldn't copy from). The post it edited to reflect this. A workaround for the issue is to call "name.toStdString().c_str()" where name is the QString, though this feels less efficient.

koahnig · 21 Jun 2017, 21:14

@mlathrop

Really a bit strange. Possibly you should post a snippet of your code showing where the problem shows up.

When you are using dlls is this self-compiled or pre-build from Qt webpage?

Also when you compile, from where do you take the code?
At least in the past there was always the recommendation to download the source code archive (.zip for windows). The source code as delivered with the pre-compiled Qt libs was not suitable for re-compilation. AFAIK this is still the case or at least I have not read the opposite yet.

mlathrop · 22 Jun 2017, 06:53

@koahnig said in Building DLL in Visual Studio with Static Linking to QT:

east in the past there was always the recommendation to download the source code archive (.zip for windows). The source code as delivered with the pre-compiled Qt libs was not suitable for re-compilation. AFAIK this is still the case or at least I have not read the

I got the dll's from the website (or actually from the installer... but all it does is download them...)

Here is a code snippet:

if (xml.isEndElement() && xml.name() == "Test") {
          int id = Add(left, right, bottom, top, front, back);
          QString adjusted_name = name;
          int i = 0;
          while (!SetName(id, adjusted_name.toLocal8Bit())) {
            adjusted_name = name + QString::number(i++);
          }
}

koahnig · 22 Jun 2017, 21:59

@mlathrop said in Building DLL in Visual Studio with Static Linking to QT:

@koahnig said in Building DLL in Visual Studio with Static Linking to QT:

east in the past there was always the recommendation to download the source code archive (.zip for windows). The source code as delivered with the pre-compiled Qt libs was not suitable for re-compilation. AFAIK this is still the case or at least I have not read the

I got the dll's from the website (or actually from the installer... but all it does is download them...)

This means that you standard pre-compiled dll version. When you have taken care of chosing the same pre-compiled version as the tool chain you are using, this should be fine.

Are you mixing std::string with QString?
When name is std::string than you a conversion.

What is the parameter in SetName?
There may apply the same.

kshegunov · wrote on 22 Jun 2017, 07:27

@mlathrop said in Building DLL in Visual Studio with Static Linking to QT:

Interestingly, things don't work when I build dynamically and link against the QT libraries either.

Then it's most probably a linking issue. Can you show how you link the Qt libraries (e.g. from your .pro file)? Also add the actual linker invocation line, so we can see what is executed exactly.

A workaround for the issue is to call "name.toStdString().c_str()" where name is the QString, though this feels less efficient.

Besides inefficient, depending on how you use that it might be much less safe ...

mlathrop · wrote on 22 Jun 2017, 21:59

@koahnig

SetName takes in a char* because it is a part of an API.

@kshegunov

Here are the relevant linker calls. I don't know how to get the .pro file from a VS project.

Here is the linker call in the project that makes the dll:

/OUT:"E:\Users\misappsci\Documents\Projects\yyy\x64\bin\yyy3D.dll" /MANIFEST /LTCG:incremental /NXCOMPAT /PDB:"E:\Users\misappsci\Documents\Projects\yyy\x64\bin\yyy3D.pdb" /DYNAMICBASE "sl_zed64.lib" "opencv_world310.lib" "cudart.lib" "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "comdlg32.lib" "advapi32.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "odbc32.lib" "odbccp32.lib" "qtmain.lib" "Qt5Core.lib" "Qt5Multimedia.lib" "Qt5Gui.lib" "winmm.lib" /IMPLIB:"E:\Users\misappsci\Documents\Projects\yyy\x64\bin\yyy3D.lib" /DEBUG /DLL /MACHINE:X64 /OPT:REF /PGD:"E:\Users\misappsci\Documents\Projects\yyy\x64\bin\yyy3D.pgd" /SUBSYSTEM:CONSOLE /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /ManifestFile:"x64\3DRelease\yyy3D.dll.intermediate.manifest" /OPT:ICF /ERRORREPORT:PROMPT /NOLOGO /LIBPATH:"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v8.0\lib\x64" /LIBPATH:"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v8.0/lib/x64" /LIBPATH:"C:\Program Files (x86)\ZED SDK\dependencies\opencv_3.1.0/x64/vc14/lib" /LIBPATH:"C:\Program Files (x86)\ZED SDK\lib" /LIBPATH:"C:\Program Files\boost\boost_1_63_0/lib/x64" /LIBPATH:"C:\Qt\5.7\msvc2015_64\lib" /TLBID:1

Here is the linker call for the project that uses the dll and has the run time error:

/OUT:"E:\Users\misappsci\Documents\Projects\Aerie\host_x64\x64\Release\AerieLib.dll" /MANIFEST /LTCG:incremental /NXCOMPAT /PDB:"E:\Users\misappsci\Documents\Projects\Aerie\host_x64\x64\Release\AerieLib.pdb" /DYNAMICBASE "Qt5Core.lib" "Qt5Gui.lib" "Qt5Multimedia.lib" "yyy3D.lib" "sl_zed64.lib" "opencv_world310.lib" "cudart.lib" "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "comdlg32.lib" "advapi32.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "odbc32.lib" "odbccp32.lib" /IMPLIB:"E:\Users\misappsci\Documents\Projects\Aerie\host_x64\x64\Release\AerieLib.lib" /DEBUG /DLL /MACHINE:X64 /OPT:REF /PGD:"E:\Users\misappsci\Documents\Projects\Aerie\host_x64\x64\Release\AerieLib.pgd" /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /ManifestFile:"x64\Release\AerieLib.dll.intermediate.manifest" /OPT:ICF /ERRORREPORT:PROMPT /NOLOGO /LIBPATH:"C:\Qt\5.7\msvc2015_64\lib" /LIBPATH:"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v8.0/lib/x64" /LIBPATH:"C:\Program Files (x86)\ZED SDK\dependencies\opencv_3.1.0/x64/vc14/lib" /LIBPATH:"C:\Program Files (x86)\ZED SDK\lib" /LIBPATH:"E:\Users\misappsci\Documents\Projects\yyy\x64\bin" /LIBPATH:"C:\Program Files\boost\boost_1_63_0/lib/x64/" /TLBID:1