issues with building QMYSQL plugin

mzimmers

@jsulm thanks for the reply. I recognize that this flag isn't compatible with my current compiler. Of greater concern to me is: where is this flag coming from? It's not in my .pro file, and none of the other projects I've built using Creator have generated this flag.

I'm looking into upgrading my compiler, but someone on the Debian forum told me that this might not be a good idea, so that's on hold for a bit.

EDIT: OK, it looks like upgrading my compiler without upgrading the version of Debian I'm running is a bad idea. At this point, it seems like it would be the tail wagging the dog anyway. So, I'm back to this question: where is that flag coming from? Does qmake actually parse the code to the point where it might detect that such a flag would be necessary?

Question #2: Sgaist referred to "an out of source build" above. I'm not sure I know what this mean -- does it mean redirecting the output of the build to another directory? If so, is this accomplished with a qmake variable? Because I didn't see one in the documentation that looked like it would alter this.

Thanks.

jsulm

@mzimmers qmake does not parse any source code, it only parses pro files. Can you post that pro file or a link to it? This flag should be in that file. You also should check the output of the qmake command, maybe it gives some hints.
Out of source simply means that you call qmake and make from a directory outside of the source code you're going to build. This way all the build artefacts are not in the source directory - you keep the source code directory clean.

mzimmers

@jsulm here's the project file. I put in the last line myself.

TARGET = qsqlmysql

HEADERS += $$PWD/qsql_mysql_p.h
SOURCES += $$PWD/qsql_mysql.cpp $$PWD/main.cpp

#QMAKE_USE += mysql

OTHER_FILES += mysql.json

PLUGIN_CLASS_NAME = QMYSQLDriverPlugin
include(../qsqldriverbase.pri)

QMAKE_CXXFLAGS -= "-std=c++1z"

I'm still getting this error, though:

/opt/Qt/5.8/Src/qtbase/mkspecs/features/qt_plugin.prf:62: error: Cannot touch /mkspecs/modules/qt_plugin_qsqlmysql.pri: Operation not permitted.

It's trying to write to mkspecs as a root directory. I verified this by running as root; it creates a mkspecs root directory. I think the cause is some undefined symbols, as the lines that form this symbol are:

38    mod_work_pfx = $$MODULE_QMAKE_OUTDIR/mkspecs/modules
44    MODULE_FWD_PRI = $$mod_work_pfx/qt_plugin_$${MODULE}.pri
62            touch($$MODULE_FWD_PRI, $$MODULE_PRI)

Thanks for any assistance.

SGaist

To avoid losing time, just copy the qtbase module sources in you home folder so you don't have that touch problem.

mzimmers

I just tried this; got a few errors. I took care of all but one:

error: Project has no top-level .qmake.conf file.

I still think there's something wrong with my variables or symbols if it was trying to write to the root directory, though.

SGaist

Did you copy the whole qtbase source ?

mzimmers

@SGaist oops...I misread what you said above...sorry. I'm still getting this error, though:

/home/mzimmers/QtStuff/qtbase/mkspecs/features/qt_plugin.prf:62: 
error: Cannot touch /mkspecs/modules/qt_plugin_qsqlmysql.pri: Operation not permitted.

I can try this with root, too, but I'm pretty sure it will indeed write to a directory /mkspecs...it did before.

SGaist

The sources likely have kept their rights. You should call something like sudo chown user:group qtbase -R (replace user and group by your user name and main group).

mzimmers

User and group IDs are already mine. (They are in the original location as well.)

SGaist

Then are the files read-only ?

mzimmers

@SGaist No, not for me:

mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$ pwd
/home/mzimmers/QtStuff/qtbase/src/plugins/sqldrivers/mysql
mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$ ls -l
total 108
-rw-rw-r-- 1 mzimmers mzimmers  2619 Jan 18 09:20 main.cpp
-rw-r--r-- 1 mzimmers mzimmers  8229 Mar 15 20:04 Makefile
-rw-rw-r-- 1 mzimmers mzimmers    40 Jan 18 09:20 mysql.json
-rw-rw-r-- 1 mzimmers mzimmers   250 Mar 15 20:06 mysql.pro
-rw-r--r-- 1 mzimmers mzimmers 23807 Mar 16 17:11 mysql.pro.user
-rw-rw-r-- 1 mzimmers mzimmers 50811 Jan 18 09:20 qsql_mysql.cpp
-rw-rw-r-- 1 mzimmers mzimmers  3952 Jan 18 09:20 qsql_mysql_p.h
-rw-rw-r-- 1 mzimmers mzimmers   204 Jan 18 09:20 README
mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$

SGaist

I just realised there's something fishy with the error message: the path seems to start at the root of the filesystem and doesn't match anything I know from the sources.

Can you try a clean out of source build of the plugin from the console ?

mzimmers

@SGaist I deleted my Makefile and ran the following command:

mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$ /opt/Qt/5.8/gcc_64/bin/qmake "INCLUDEPATH+=/usr/local/include /usr/src/mysql/mysql-5.7.17/include" "LIBS+=-L/usr/lib -lmysqlclient_r" /home/mzimmers/QtStuff/qtbase/src/plugins/sqldrivers/mysql/mysql.pro

Question #1: what is the correct syntax for removing a compiler flag? I tried this:

QMAKE_CXXFLAGS -= "-std=c++1z"

but that didn't work.

I then went in and manually modified the Makefile, changing "-std=c++1z" to "-std=c++11", and ran make. I then encountered this error:

mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$ make
g++ -c -pipe -O2 -std=c++11 -fvisibility=hidden -fvisibility-inlines-hidden -fno-exceptions -Wall -W -Wvla -Wdate-time -D_REENTRANT -fPIC -DQT_NO_CAST_TO_ASCII -DQT_NO_CAST_FROM_ASCII -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_PLUGIN -DQT_SQL_LIB -DQT_CORE_LIB -I. -isystem /usr/local/include -I/usr/src/mysql/mysql-5.7.17/include -I/opt/Qt/5.8/gcc_64/include/QtSql/5.8.0 -I/opt/Qt/5.8/gcc_64/include/QtSql/5.8.0/QtSql -I/opt/Qt/5.8/gcc_64/include/QtCore/5.8.0 -I/opt/Qt/5.8/gcc_64/include/QtCore/5.8.0/QtCore -I/opt/Qt/5.8/gcc_64/include -I/opt/Qt/5.8/gcc_64/include/QtSql -I/opt/Qt/5.8/gcc_64/include/QtCore -I.moc -I../../../../mkspecs/linux-g++ -o .obj/qsql_mysql.o qsql_mysql.cpp
In file included from qsql_mysql_p.h:60:0,
                 from qsql_mysql.cpp:40:
/usr/src/mysql/mysql-5.7.17/include/mysql.h:57:27: fatal error: mysql_version.h: No such file or directory
 #include "mysql_version.h"
                           ^
compilation terminated.
Makefile:834: recipe for target '.obj/qsql_mysql.o' failed
make: *** [.obj/qsql_mysql.o] Error 1
mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$

I don't have a file named mysql_version.h. I do have a file named mysql_version.h.in. I'm not familiar with .in files, but according to Wiki, it's input to a program called "autoconf." In reading the documentation, I wonder whether I somehow missed a step in the build that converts this .in file into a .h file. EDIT: I did find a cmake file with that name as well, though there's nothing in the documentation about running cmake manually.

Anyway, we do seem to be moving forward. I would like to resolve this problem with the compiler flag, though.

Thanks for all the help.

SGaist

Out of curiosity, why don't you install the MySQL dev package from your distribution ? That would certainly simplify things.

As for your compiler, which version is it ?

mzimmers

MySQL doesn't make a package for Debian. The compiler is 4.9.2. I asked about updating the compiler in a Debian forum, and got a lot of snarky answers telling me it was a bad idea.

SGaist

Sure there is: see libmysqlclient-dev.

IIRC 4.9.2 should be good to build Qt 5.

mzimmers

@SGaist I'm sorry; I misunderstood you -- when you said "from your distribution," I thought you meant part of the Debian package.

Just to be clear, are you saying that with that package, I can better build the QMYSQL plugin, or that it's already included?

And, for my education, I'd really like to know how to alter compiler flags on the command line. I've tried "QMAKE_CXXFLAGS -=" but that doesn't seem to do anything.

Thanks.

SGaist

It will make things easier to build the plugin.

IIRC CONFIG += c++11 should only enable C++11 feature and not later.

mzimmers

@SGaist I think we're getting closer. I installed the package you referenced above, and ran this qmake command:

/opt/Qt/5.8/gcc_64/bin/qmake "INCLUDEPATH+=/usr/include" "LIBS+=-L/usr/lib/x86_64-linux-gnu/ -lmysqlclient_r" /home/mzimmers/QtStuff/qtbase/src/plugins/sqldrivers/mysql/mysql.pro/

I then edited the Makefile, changing the 2 occurrences of "-std=c++1z" to "-std=c++11" and ran make. Here's the output:

mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$ make
rm -f libqsqlmysql.so
g++ -Wl,--no-undefined -Wl,-O1 -Wl,--enable-new-dtags -Wl,-z,origin -Wl,-rpath,\$ORIGIN/../../lib -Wl,-rpath,\$ORIGIN/../../lib -shared -o libqsqlmysql.so .obj/qsql_mysql.o .obj/main.o .obj/moc_qsql_mysql_p.o  -L/usr/lib -lmysqlclient_r -L/opt/Qt/5.8/gcc_64/lib -lQt5Sql -lQt5Core -L/usr/lib64/mysql -lmysqlclient -lpthread -lz -lm -lssl -lcrypto -ldl  
/usr/bin/ld: cannot find -lmysqlclient_r
collect2: error: ld returned 1 exit status
Makefile:115: recipe for target '../../../../plugins/sqldrivers/libqsqlmysql.so' failed
make: *** [../../../../plugins/sqldrivers/libqsqlmysql.so] Error 1
mzimmers@debian:~/QtStuff/qtbase/src/plugins/sqldrivers/mysql$

I also tried LIBS+=-L/usr/lib/x86_64-linux-gnu (which is the actual directory) with the same results. Any idea what's wrong here?

Thank you.

SGaist

You shouldn't need the -l parameter