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SQL/Doc: improve documentation on building and debugging a sql driver

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Add some notes on the prerequisites when building a sql driver from
source and also add some more notes in the troubleshooting section.

Pick-to: 6.7 6.5
Change-Id: I8ffbcf4182c2ad2c7b9f86209e0ce332fd27d73c
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 1f31c5f3cd722f06e4f41457ec1322365d78c018)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Christian Ehrlicher 2024-08-17 20:19:10 +02:00 committed by Qt Cherry-pick Bot
parent c9fe636dfc
commit da87068f7f
1 changed files with 28 additions and 10 deletions
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38
src/sql/doc/src/sql-driver.qdoc
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@ -82,7 +82,14 @@
directory.
\target DriverStandalone
\section2 Compile only a specific sql driver
\section2 Compile only a specific SQL driver
It's possible to only compile a specific SQL driver when Qt is already built
or installed as binary version. But you have to make sure to install
the exact same version of the Qt sources (for example through the \QMT) -
otherwise you might get compile errors due to changed apis.
Also make sure to properly set up the build environment by executing the
appropriate Qt command prompt in the Windows Start menu.
A typical \c qt-cmake run (in this case to configure for MySQL) looks like this:
@ -932,26 +939,37 @@
a source distribution to compile the client libraries yourself, you
must make sure that the pre-compiled library is compatible with
your compiler, otherwise you will get a lot of "undefined symbols"
errors. Some compilers have tools to convert libraries, e.g. Borland
ships the tool \c{COFF2OMF.EXE} to convert libraries that have been
generated with Microsoft Visual C++.
errors.
If the compilation of a plugin succeeds but it cannot be loaded,
make sure that the following requirements are met:
If the compilation of a plugin succeeds but it cannot be loaded
afterwards, check out the following steps to find out the culprit:
\list
\list 1
\li Ensure that the plugin is in the correct directory. You can use
QApplication::libraryPaths() to determine where Qt looks for plugins.
\li Ensure that the client libraries of the DBMS are available on the
system. On Unix, run the command \c{ldd} and pass the name of the
plugin as parameter, for example \c{ldd libqsqlmysql.so}. You will
get a warning if any of the client libraries could not be found.
On Windows, you can use Visual Studio's dependency walker. With
On Windows, you can use Visual Studio's dependency walker or
\l{https://github.com/lucasg/Dependencies/releases}{Dependencies GUI}
to find out the dependent libraries. With
Qt Creator, you can update the \c PATH environment variable in the
\gui Run section of the \gui Project panel to include the path to
the folder containing the client libraries.
\li Compile Qt with \c{QT_DEBUG_PLUGINS} defined to get very verbose
debug output when loading plugins.
\li When using MSVC, also make sure the plugin is built with the correct
build type. Due to different MSVC runtimes for debug and release,
a Qt debug build can't load a Qt release plugin and vice versa.
\li Run the compiled Qt executable with the environment variable
\l{Environment Variables Recognized by Qt}{QT_DEBUG_PLUGINS} set
to get very verbose debug output when loading plugins.
\li To retrieve possible debug messages from the SQL subsystem, enable
the output by setting the environment variable \c{QT_LOGGING_RULES}
to \c{qt.sql.*.debug=true}. Don't forget to enable the
\l{Environment Variables Recognized by Qt}{console} when working on
windows.
See \l{Logging Rules} for a more detailed explanation on how to set
logging rules.
\endlist
Make sure you have followed the guide to \l{Deploying Plugins}.