Qt already updated to 5.14.1, but why it still uses MSVC 2017 build tools?

BAHRAMUDIN ADIL

@aha_1980 The first thing is the warning which Qt gives me which says: Qt is not compatible with MSVC 2019. OK, this is a warning so skip it.

But the error is I am not able to use MySQL drivers to connect to the database, I have already added the DLL and libs into Qt bin and in my project as well, but still not working and gives error while compiling, and when I switch to another machine which has the same version of Qt but MSVC 2017 installed it works well. Then how to explain this?

Thanks!

J.Hilk

The Qt Framework is big, has lots of features and modules and classes.

If the new compiler only has marginal changes (like one clang/gcc version to an other) you can rather safely upgrade/support the new version after reading the changelog.

Microsoft until recently, totally broke binary compatibility with each MSVC release and god only knows what they are currently doing.

So upgrading / supporting a new MSVC version will require extensive testing and I assume that's simply not yet done/finished.

I personally already run into Qtmsvc2017 and 2019 incompatibility issues. The Qt support answered me with: Thanks for the report we will look into it, but 2019 is not yet officially supported, we suggest to use 2017.
And that's what I ended up doing.

I only used msvc2019 in the first place, because MS makes ist unnecessarily difficult to download older compiler version!😡

What msvc2019 feature is so important that you have to use that compiler ?

gives error while compiling,

what error?

BAHRAMUDIN ADIL

@J-Hilk Thanks for the explanation. I know it is not an easy job needs a lot of tests, but on the other hand, if you persist to do not support the newer version, then it may cause to lose your users by the time because people they going to use the newer version and leave the older one some of them because of security problem, some of them maybe because of compatibility problem.
You asked me why I want to use MSVC 2019? It is because I am using some libs which recommended to MSVC 2019. And our team development is based on MSVC 2019.

BAHRAMUDIN ADIL

@J-Hilk One problem I am getting while using Qt with MSVC 2019, my code not getting compiled:

main.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl QSqlDatabase::~QSqlDatabase(void)" (__imp_??1QSqlDatabase@@QEAA@XZ) referenced in function main

But same code works well with Qt + MSVC 2017.

Christian Ehrlicher

@BAHRAMUDIN-ADIL said in Qt already updated to 5.14.1, but why it still uses MSVC 2017 build tools?:

But same code works well with Qt + MSVC 2017.

I doubt that - I would guess you don't link against the Qt sql library. Please show us your .pro file and/or make sure you're linking against the correct libraries you need.

BAHRAMUDIN ADIL

@Christian-Ehrlicher It is the .pro file content:

QT -= gui

CONFIG += c++11 console sql
CONFIG -= app_bundle

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        main.cpp

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

I have all the DLL and libs files in the Qt installed location bin/lib folder.

SimonSchroeder

According to the documentation (https://doc.qt.io/qt-5/qsqldatabase.html) you should add

QT += sql

to your .pro file. This tells the compiler to link with the SQL plugin.

BAHRAMUDIN ADIL

@SimonSchroeder Thanks! I will try it.

SGaist

@BAHRAMUDIN-ADIL said in Qt already updated to 5.14.1, but why it still uses MSVC 2017 build tools?:

@SimonSchroeder If you see carefully I have already added sql

To the wrong variable. You added it to CONFIG but you shall add it to QT as @SimonSchroeder wrote.

[edit: Answer to the original post SGaist]

BAHRAMUDIN ADIL

@SimonSchroeder Yes, I did not add the SQL module correctly in .pro file. But now I got this error:

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7

BAHRAMUDIN ADIL

@SGaist Hmmm, yes, it was my fault, but now I got the next error, what is your opinion?
I have already added these two DLL files in Qt bin directory:

libmysqld.dll
libmysql.dll

And also I have tried these three as well:

ssleay32.dll
libeay32.dll
libmysql.lib

Also not solved the problem.

J.Hilk

@BAHRAMUDIN-ADIL
after modifying your pro file, ALWAYS clean and run qmake

you added a new module so I would go a step further and delete the build directory for a complete rebuild

BAHRAMUDIN ADIL

@J-Hilk Yes, I did that as you said, but the problem still exists. Can you tell me what files and libs I need to add and add them in which place? Thanks!

SGaist

@BAHRAMUDIN-ADIL said in Qt already updated to 5.14.1, but why it still uses MSVC 2017 build tools?:

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7

As you can see from the listing, you don't have the plugin at all.

As for why: the licensing of MySQL changed so only GPL and Commercial are available now. Since the pre-built binaries are usable also under the LGPL, the plugin can't be provided.

You also have the option of building it with MariaDB which fixes the licensing issue.

See QTBUG-78241

BAHRAMUDIN ADIL

@SGaist You mean that I need to build Qt from source with the needed plugins? Or I just need to build the MySQL plugin? If the second case is right, then to build the only plugin, what should I need, and how to build? Is there any guide to show how to build?
Thanks!

aha_1980

@BAHRAMUDIN-ADIL

you need to build the plugin as described here: https://doc.qt.io/qt-5/sql-driver.html#qmysql

Regards

BAHRAMUDIN ADIL

@aha_1980 Yes, before you send me the answer I saw this documentation, but can you tell me where is it?

cd %QTDIR%\qtbase\src\plugins\sqldrivers

I did not find in whole Qt installation directory.

Thank you so much!!!

Christian Ehrlicher

@BAHRAMUDIN-ADIL said in Qt already updated to 5.14.1, but why it still uses MSVC 2017 build tools?:

I did not find in whole Qt installation directory.

As you can see there is 'src' - you need the Qt sources...

BAHRAMUDIN ADIL

@Christian-Ehrlicher Hmmm, so for a small plugin I need to download the whole Qt source code? It definitely takes a lot of time and takes much space. I think the Qt team should think about it to make it easy just to download only what I need not all the source code or provide some other way to overcome this problem because MySql users are very a lot on all over the world. If all the users download the source code it will so be extra pressure on Qt side server and also not good user experience.

I hope the Qt becomes more beautiful in the feature!!

aha_1980

@BAHRAMUDIN-ADIL You don't need to tell us - we are just users like you and not related to the Qt company.

You might also want to use the MariaDB plugin which does not have the MySQL licence restrictions.

Btw: you can download the sources with the MaintenanceTool.

Regards