Stupid Windows Compilation Trick

[wysota]

Well, my development environment is Qt Creator 2.0 for Windows.

I don't mean Creator. I mean your include files and such.

As far as my includes, i looked down the chain, and it is mostly Qt classes that are included, and a few other things like cdio.

If you are using ::write() then it's somethine more than just Qt. Some library is probably screwing up your compilation.

Any way I can check the include chain to find anything suspicious?

I doubt it is anything obvious.

Like I said before, the most frustrating thing is, that this exact code compile fine under Linux using gcc, but fails under Windows using mingw.

If your Windows files destroy the compilation then I can believe that happening. I've already seen it

You can do two things. First start getting rid of include files (and code that uses it) until the compilation starts working again - then you'll know which file is the first in chain of causing the problem. The other thing you can do is take the file the compiler complains about, open it on the line it complains about and read carefully everything that is before this line - maybe you will spot something disturbing. Especially pay attention to macros defined and grep your includes for them. It could be that one library relies on a macro being defined and some other library undefines it because of some reason.

[skepticalgeek]

Thanks for the help. I struggled with the issue all weekend, and finally solved it by changing the order of the includes in the header file for the form. It took me a while to find the exact sequence. Any flags I can pass to Qmake or MinGw so that it will be smart enough to figure this out on it's own, without me having to guess at which order it wants the include statements in?

[wysota]

Any flags I can pass to Qmake or MinGw so that it will be smart enough to figure this out on it's own, without me having to guess at which order it wants the include statements in?

No, it's not possible. Consider the following two include files:

// A.h
#ifndef SOME_VAR
#define SOME_VAR 1
#endif

// A.h
#ifndef SOME_VAR
#define SOME_VAR 1
#endif

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// B.h
#ifndef SOME_VAR
#define SOME_VAR 2
#endif

// B.h
#ifndef SOME_VAR
#define SOME_VAR 2
#endif

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and then:

// main.cpp
#include <A.h>
#include <B.h>

// main.cpp
#include <A.h>
#include <B.h>

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It's not possible to determine if this is a correct include order or not without knowing the effect you want to achieve. The compiler can't do it for you.

[skepticalgeek]

Fair enough. Any idea why the original compilation order worked under Linux, and choked under Windows? Same code,same IDE (Qt Creator), same header files for the 3rd party libraries. The only difference is I was linking to 3rd party DLLs in the pro file, instead of 3rd party .so files.

[wysota]

Fair enough. Any idea why the original compilation order worked under Linux, and choked under Windows? Same code,same IDE (Qt Creator), same header files for the 3rd party libraries.

... different defines active for each platform in those same files.

[skepticalgeek]

Well, the multiple definition errors are back again, and this time they mean business. I though everything was working, until I made a minor code change, and kaboom! Here they come back for more. Here is a sample of the output, I ran into the character limit trying o post all of it:

In function `Z17qVariantFromValueI8QVariantES0_RKT_':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:453: multiple definition of `QVariant qVariantFromValue<QVariant>(QVariant const&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:453: first defined here
./debug\moc_frmrip.o: In function `Z16qVariantSetValueI8QVariantEvRS0_RKT_':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:475: multiple definition of `void qVariantSetValue<QVariant>(QVariant&, QVariant const&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:475: first defined here
./debug\moc_frmrip.o: In function `QVariant':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:480: multiple definition of `QVariant::QVariant()'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:480: first defined here
./debug\moc_frmrip.o: In function `QVariant':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:480: multiple definition of `QVariant::QVariant()'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:480: first defined here
./debug\moc_frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:481: multiple definition of `QVariant::isValid() const'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:481: first defined here
./debug\moc_frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:536: multiple definition of `QVariant::isDetached() const'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:536: first defined here
./debug\moc_frmrip.o: In function `ZeqRK8QVariantRK24QVariantComparisonHelper':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:558: multiple definition of `operator==(QVariant const&, QVariantComparisonHelper const&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:558: first defined here
./debug\moc_frmrip.o: In function `ZneRK8QVariantRK24QVariantComparisonHelper':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:563: multiple definition of `operator!=(QVariant const&, QVariantComparisonHelper const&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:563: first defined here
./debug\moc_frmrip.o: In function `Z13qvariant_castI8QVariantET_RKS0_':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:583: multiple definition of `QVariant qvariant_cast<QVariant>(QVariant const&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:583: first defined here
./debug\moc_frmrip.o: In function `Z11qIsDetachedI8QVariantEbRT_':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:601: multiple definition of `bool qIsDetached<QVariant>(QVariant&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:601: first defined here
./debug\moc_frmrip.o: In function `Z5qSwapI8QVariantEvRT_S2_':
C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:601: multiple definition of `void qSwap<QVariant>(QVariant&, QVariant&)'
./debug\frmrip.o:C:\SKG_Jukebox/../Qt/2010.04/qt/include/QtCore/../../src/corelib/kernel/qvariant.h:601: first defined here
collect2: ld returned 1 exit status
mingw32-make[1]: *** [SKG_Jukebox.exe] Error 1
mingw32-make: *** [debug] Error 2
The process "C:/Qt/2010.04/mingw/bin/mingw32-make.exe" exited with code %2.
Error while building project SKG_Jukebox (target: Desktop)
When executing build step ''

The problems seem to be coming from my moc object files. It looks like qmake is making defective files, then the compiler is complaining about the multiple definitions. I am not putting this in my code. I am not making up new definitions of basic Qt objects and functions, and then wondering why they don't compile. I checked my pro file 3 times, no duplicate entries in the file list. Here it is though, if it can help anyone figure this out.

# -------------------------------------------------
# Project created by QtCreator 2010-01-22T23:16:56
# -------------------------------------------------
QT += network \
phonon \
xml
TARGET = SKG_Jukebox
TEMPLATE = app
SOURCES += main.cpp \
SKG_RoundButton/skg_roundbutton.cpp \
jukeboxconfig.cpp \
SKG_AlbumPanelSmall/skg_albumpanelsmall.cpp \
SKG_AlbumPanelSmall/skg_albumpanelframesmall.cpp \
SKG_AlbumPanel/skg_albumpanel.cpp \
SKG_AlbumPanel/skg_albumpanelframe.cpp \
SKG_AlbumWidget/skg_albumwidget.cpp \
SKG_AlbumWidget/skg_albumframe.cpp \
lib/skglib.cpp \
SKG_Button/skg_button.cpp \
mainnetbook.cpp \
mainnormal.cpp \
frmrip.cpp \
frmtracklist.cpp \
frmoptions.cpp \
googleimagesearch.cpp \
yahooimagesearch.cpp \
frmalbumart.cpp \
frmalbumartdialog.cpp \
frmalbumartmulti.cpp \
customalbumlist.cpp \
customlistmanager.cpp \
frmloadcustomlist.cpp \
frmconfig.cpp \
frmaddeditlist.cpp \
keytranslator.cpp \
# ogg_encoder.cpp \
mp3_encoder.cpp \
# flac_encoder.cpp \
cd_extractor.cpp \
frmdialog.cpp \
playlist.cpp \
playlistmanager.cpp \
frmaddeditplaylist.cpp \
frmloadplaylist.cpp \
frmsplash.cpp \
freedblookup.cpp
HEADERS += SKG_RoundButton/skg_roundbutton.h \
jukeboxconfig.h \
SKG_AlbumPanelSmall/skg_albumpanelsmall.h \
SKG_AlbumPanelSmall/skg_albumpanelframesmall.h \
SKG_AlbumPanel/skg_albumpanel.h \
SKG_AlbumPanel/skg_albumpanelframe.h \
SKG_AlbumWidget/skg_albumwidget.h \
SKG_AlbumWidget/skg_albumframe.h \
lib/skglib.h \
SKG_Button/skg_button.h \
mainnetbook.h \
mainnormal.h \
frmrip.h \
frmtracklist.h \
frmoptions.h \
googleimagesearch.h \
yahooimagesearch.h \
frmalbumart.h \
frmalbumartdialog.h \
frmalbumartmulti.h \
customalbumlist.h \
customlistmanager.h \
frmloadcustomlist.h \
frmconfig.h \
frmaddeditlist.h \
keytranslator.h \
# ogg_encoder.h \
mp3_encoder.h \
# flac_encoder.h \
cd_extractor.h \
frmdialog.h \
playlist.h \
playlistmanager.h \
frmaddeditplaylist.h \
frmloadplaylist.h \
frmsplash.h \
freedblookup.h
FORMS += mainnetbook.ui \
mainnormal.ui \
SKG_AlbumPanelSmall/skg_albumpanelframesmall.ui \
SKG_AlbumPanel/skg_albumpanelframe.ui \
SKG_AlbumWidget/skg_albumframe.ui \
frmtracklist.ui \
frmoptions.ui \
frmalbumart.ui \
frmalbumartdialog.ui \
frmalbumartmulti.ui \
frmloadcustomlist.ui \
frmconfig.ui \
frmaddeditlist.ui \
frmrip.ui \
frmdialog.ui \
frmaddeditplaylist.ui \
frmloadplaylist.ui \
frmsplash.ui

LIBS += -LC:\Qjson\lib -lqjson0 \
-LC:\SKG_Jukebox\dll \
-llibcdio-10 \
-llibcdio_cdda-0 \
-llibcdio_paranoia-0 \
-llame_enc

At this point, I no longer care why this is occurring. I just want it to stop. I want to know which arguments I can pass to qmake or mingw-make32, to get it to stop creating object files with multiple definitions of standard Qt classes, or to ignore them in the compilation process. I don't feel I should have to play guessing games with the preprocessor, to determine which Qt include files I can and cannot include in my objects. I just want Qt creator, and the tools it is using, to stop prison raping me, and compile what I wrote, in the absence of syntax errors. Again, this exact project compiles and runs like a dream in Linux. What is it about Qt in Windows that it wants to make my life miserable. And it all started when I tried adding this one form. There are over a dozen forms in this project, and it is only this one, FrmRip, that caused all this. Before this, the project compiled and ran fine under Windows. There is nothing in the include chain in this form except Qt headers, and some third party headers that I know are not the problem. I can post the includes here, if that will help anyone. Sorry if I came off a little too angry, but I am tired of wrestling with this, and getting desperate.

[wysota]

It's not that simple. There is no "--dont-throw-errors-on-me" compiler switch. Begin with a simple project, start adding files (and code) to it until it stops compiling. Then you'll know where to look for the problem.

[skepticalgeek]

I wasn't looking for a "don't throw errors" switch. I don't object to the compiler throwing errors. I object to it throwing errors on stuff I didn't write. I didn't create multiple definitions of all these Qt objects, qmake or the linker did. I want them to stop doing that. Failing that, I was looking for something like a /FORCE switch in Visual Studio, or something like an ignore multiple definitions switch.

That said, I appreciate the time you've taken to try to help me on this. I'm just frustrated. As far as I can tell, I haven't done anything but include standard Qt headers in a Qt project, then watched the compiler tell me to screw myself. For some reason, that stops being fun after about a week.

[wysota]

I didn't create multiple definitions of all these Qt objects, qmake or the linker did.

No, they didn't.

I want them to stop doing that.

So don't use 3rd party libraries that break your compilation.

Failing that, I was looking for something like a /FORCE switch in Visual Studio, or something like an ignore multiple definitions switch.

Sure. Assuming you have the following two definitions of the same method:

bool func() { return true; }
bool func() { return false; }

bool func() { return true; }
bool func() { return false; }

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Which one would you like for the compiler to ignore automatically?

I'm just frustrated.

Don't be. Just do what I suggested.

As far as I can tell, I haven't done anything but include standard Qt headers in a Qt project, then watched the compiler tell me to screw myself. For some reason, that stops being fun after about a week.

But you can't blame Qt for that. From what I see you are using 3rd party libraries that have their own includes and own functions/classes. You can't call that including only "standard Qt headers in a Qt project". I'm sure that if you remove all those non-Qt includes (and of course code related to them), your application will compile just fine.