QMYSQL driver not loaded on mac

[LuAria]

Actually, I'm a nook on QT and MySQL.
Platform: OS X 10.12.6```
Qt 5.9.1
MySQL 5.7.18
Code:
QSqlDatabase data_base = QSqlDatabase::addDatabase("QMYSQL");
data_base.setHostName("127.0.0.1");
data_base.setPort(3306);
data_base.setDatabaseName("student.db");
data_base.setUserName("root@localhost");
data_base.setPassword("lulu168168");

~.pro included QT+=sql

but the result was：
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QP
SQL7
failed to connect to mysql

I haved read lots of anwers on the net. However, I was so upset that I can not find /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib.
What's more, otool -L libqsqlmysql.dylib led to /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/objdump: 'libqsqlmysql.dylib': No such file or directory.
Who can help me T^T.
Thanks very much!!!!

[SGaist]

Hi and welcome to devnet,

MySQL is not installed by default on macOS, so you first have to install it. If you don't have any version of MySQL on your system you can use for example macports which from the looks of it was used for the dependencies when building the Qt package you installed.

Your other error indicates that you don't have any file name libqsqlmysql.dylib in the folder were you called otool.

[LuAria]

Thanks for your quick response very much !!!!
I haved already installed MySQL. The version is 5.7.18. I can find MySQL file in /usr/local. There's only 2 folders in /opt: X11 and the other.
I think I cannot express myself well.
I'm using cellphone now.
Maybe I can show my screenshots hours later.
Thanks for your answer agian !!!

[SGaist]

Then you have to use otool install_name_tool to change the path from /opt/etc... to your own installation of MySQL.

[edit: fixed tool name... SGaist]

[LuAria]

Thanks a lot.
I think I get your point.
Could you tell me more details of otool? thanks!
What's more, is there no problem that use tool to change that even /opt/etc not exist in my pc?

[SGaist]

Sorry, I meant install_name_tool.

[LuAria]

Sorry, could you tell me the whole sentence of install_name_tool.
I used install_name_tool -change /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib /usr/local/Cellar/mysql/5.7.19/lib/libmysqlclient.dylib libqsqlmysql.dylib for the Net. But it failed: error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/install_name_tool: can't open file: libqsqlmysql.dylib (No such file or directory)
I can find libmysqlclient.20.dylib and libmysqlclient.dylib both in /mysql and /mysql-5.7.18-...
What should I do?

[LuAria]

I tried install_name_tool -change /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib /usr/local/Cellar/mysql/5.7.19/lib/libmysqlclient.20.dylib

and it showed me: Usage: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/install_name_tool [-change old new] ... [-rpath old new] ... [-add_rpath new] ... [-delete_rpath old] ... [-id name] input

What did it mean?

[SGaist]

From what you wrote, you seem to be somewhere on your filesystem and just expecting that libqsqlmysql.dylib is there.

You have to give the full path to the Qt MySQL plugin if you're not in the folder where that file reside.

[LuAria]

In fact, I used find ~ -iname "libqsqlmysql"*
and found that
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib.dSYM
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib.dSYM/Contents/Resources/DWARF/libqsqlmysql.dylib
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql_debug.dylib
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql_debug.dylib.dSYM
/Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql_debug.dylib.dSYM/Contents/Resources/DWARF/libqsqlmysql_debug.dylib
/Users/lujinliang/Qt5.9.1/Qt Creator.app/Contents/PlugIns/sqldrivers/libqsqlmysql.dylib
It seemed that 'libqsqlmysql' all in the /Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers
Should I use
install_name_tool -change /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib /usr/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib
to change the path
Thanks.

[LuAria]

I used install_name_tool -change /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib /usr/local/mysql/lib/libmysqlclient.20.dylib /Users/lujinliang/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib
and finally success connected.
I want to know whether it is the correct way.
Thanks.

[SGaist]

Yes, it is.

Note that when doing such a thing you have to do some testing, you are now using a client library which is from a different version that the one used to link the plugin. That may or may not work depending on the library. In this case, things look fine.

[LuAria]

Thanks a lot.
Things look good.
Also, I want to know why QT need a strange way like /opt/local/myspl/lib/etc to connect MySQL. Is it the default way?
P.S. it is not a problem, I just want to know.
Thanks again.

[SGaist]

There's nothing strange here, the CI is likely using macports to get the dependencies it needs to build the plugins and macports installs its stuff by default in /opt.

Setting up a build machine using a package manager will always be easier than having to grab tons of installers. It's usually also simpler to handle upgrades and parallel installations with these kind of tools.

[tk421]

I'm also using Qt 5.9 on macOS and initially had a similar problem with the MySQL driver not working, and solved it using install_name_tool very much as was described above. In my case, MySQL was installed on my Mac with Homebrew.

However, now that I'm deploying the application I find that it works on my development Mac but not on other Macs. This makes sense: the libqsqlmysql.dylib in the app bundle, in the Plugins/sqldrivers directory depends on finding libmysqlclient.18.dylib in the location Homebrew uses. At the same time this doesn't make sense: how could this be the right way to do this?

I've read a lot of posts about this issue, but haven't found anything that addresses this issue: how do I configure the plugin so that it will work on other Macs, not just ones that happen to have MySQL installed in the way I have it installed?

Many users of my application don't even have MySQL installed. They are using my app to connect to a MySQL server on another server. I know this should be possible, because this app worked fine for my users for several years when I had it under Qt4. I'm just encountering this question because of a necessary upgrade to Qt5.

[SGaist]

Copy the library in your app bundle and use install_name_tool again to point the MySQL plugin to that library.

[Hasan Vaez]

Hi guys,
I have the same problem, but the above solutions and also all the solutions on the web do not work for me.
I am using Mac OS X Sierra, Qt5.9.1 installed at Home directory, Mysql 5.7.19 at /usr/local/mysql.
I would be pleased to help me to solve my problem on connection to QMSQL plugin.
I am wonder while all the new users has the same problem why Qt does not fix this bug which is seen in most of versions and claimed by many users. Half of the users' questions are about connecting to QMYSQL which is a real part of programming.
The error is:
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7
QSqlError("", "Driver not loaded", "Driver not loaded")

The stuffs I have done:
1- hasan-mac:/ hasan$ otool -L libqsqlmysql.dylib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/objdump: 'libqsqlmysql.dylib': No such file or directory
2- linking the /usr/local/mysql/lib/libmysqlclient.20.dylib(and libmysqlclient.dylib) to /usr/lib
I think I could not run install_name_tool in the right way.
need your help please as I waste 2days searching the web for creating plugins and installing libs and so on...

regards,

[SGaist]

Hi and welcome to devnet,

1. This won't work because you are calling otool in some random place where libqsqlmysql.dylib is not located. Either give the full path to the plugin or cd into the sql plugins folder in your Qt installation and call that command again.

2. Likely for the same reason as number 1.

[Hasan Vaez]

Hi SQaist,
Thank you for your prompt reply.
The result on otool is:
MacBook-Pro:sqldrivers hasan$ otool -L /Users/hasan/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib
/Users/hasan/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib:
libqsqlmysql.dylib (compatibility version 0.0.0, current version 0.0.0)
@rpath/QtSql.framework/Versions/5/QtSql (compatibility version 5.9.0, current version 5.9.1)
@rpath/QtCore.framework/Versions/5/QtCore (compatibility version 5.9.0, current version 5.9.1)
/System/Library/Frameworks/DiskArbitration.framework/Versions/A/DiskArbitration (compatibility version 1.0.0, current version 1.0.0)
/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit (compatibility version 1.0.0, current version 275.0.0)
/opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib (compatibility version 18.0.0, current version 18.0.0)
/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 120.1.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1226.10.1)

[Hasan Vaez]

Tried to use the following command and problem solved.
install_name_tool -change /opt/local/lib/mysql55/mysql/libmysqlclient.18.dylib /usr/local/mysql/lib/libmysqlclient.20.dylib /Users/hasan/Qt5.9.1/5.9.1/clang_64/plugins/sqldrivers/libqsqlmysql.dylib

The thing I am worry about is when I will face to problem as we tricked to Qt to use libqslmysql.20.dylib instead of the the one in version 18 (libmysqlclient.18.dylib).
Mainly the problem is solved but it should not be OK. I am looking for a way to solve the problem in a correct way and do not want to use MACPORTS for installing the QMYSQL module. MACPORTS is a good installation package, but its size is more than 1GB in HDD and I'd prefer to use certified sourced like mysql.com website and qt.io website and so on...