How to suppress warnings in qmake for clang++

andre

If possible at all: warnings should be fixed instead of ignored. Seriously. If you are not going to use a variable, be explicit about and either:

remove the argument completely from the function, or

remove the name of the argument from the function, or

use a construct like Q_UNUSED(myVariable) to be explicit about you not using the argument.

But don't just ignore the warning. Warnings are there for a reason. The may point to more severe issues or may develop into real problems later on.

bdemirkir

Thanks for the info but I already know these rule of thumbs. I actually follow these rules. But this is not my project. This is a third party library and i'm not allowed to edit these library's source code. It's library writer's responsibility. I just want to suppress these warnings by editing pro file.

In gcc @QMAKE_CXXFLAGS = -Wno-unused-variable@ should do the trick but in ==clang++== this method didn't work.

Any suggestions?

koahnig

[quote author="miroslav" date="1324471099"]@koahnig: The fact that Qt triggers a lot of warnings is actually quite annoying. From a code quality perspective, warnings have a urgency similar to errors, IMO. Often the only warnings that are impossible to get rid off are the ones generated by Qt itself.[/quote]

Yes, I agree completely. The first time I was compiling Qt libs it was a shock to me when seeing the warnings. However, I (have) arranged myself with it.

I am certainly agreeing also with Andre. He is summarizing my coding ethics.

My answer was refering to the compilation of the Qt libs.

On the other hand I find it more than a bit annoying that I have to clatter my code with pragmas for ignoring warnings when a Qt header is included. IMHO that is a nogo, but on an individual basis you are fighting against windmills there.

miroslav

Agreed. I do understand that it is hard to make sure no warnings are issued by any compiler. The issue could get a bit more focus, though.

bdemirkir

Here's my console output for an unexpected warning generation:

@clang++ -c -pipe -Wno-unused-variable -Wno-deprecated-writable-strings -O2 -arch x86_64 -fPIC -Wall -W -DQT_NO_DEBUG -DQT_CORE_LIB -DQT_SHARED -I/usr/local/Trolltech/Qt-4.8.0/mkspecs/unsupported/macx-clang -I. -I/usr/local/Trolltech/Qt-4.8.0/lib/QtCore.framework/Versions/4/Headers -I/usr/local/Trolltech/Qt-4.8.0/include/QtCore -I/usr/local/Trolltech/Qt-4.8.0/include -I. -I. -F/usr/local/Trolltech/Qt-4.8.0/lib -o ltkcpp_genout.o ltkcpp_genout.cpp
In file included from ltkcpp_genout.cpp:27:
./out_ltkcpp.inc:1312:3: warning: unused label 'missing' [-Wunused-label]
missing:
^
./out_ltkcpp.inc:1321:33: warning: unused variable 'pType' [-Wunused-variable]
const CTypeDescriptor * pType;
^@

As you can see i passed ==-Wno-unused-variable== parameter but clang++ still generates unused-variable error.

koahnig

Just poking in the dark. But I have noticed that there is a -Wall after -Wno-unused-variable.
Could it be that you switching off the warning and switching it on with -Wall ?
I do not know this compiler.

bdemirkir

Oh! Yes that's what i'm missing. @koahnig Thank you very much. I should avoid using warn_on CONFIG directive.

tjrob

The problem with CONFIG += warn_off is that you don't get any warnings, but without it I get hundreds of useless warnings from a library. Adding -W flags to CPPFLAGS or QMAKE_CXXFLAGS doesn't help, because the warn_on generates a -Wall that comes after them.

SOLUTION: In the .pro file:
QMAKE_CXXFLAGS_WARN_ON = -Wall -Wno-unused-parameter

This sets the flags used when warn_on appears in CONFIG (the default). Now they are in the right order.

digorydoo

+1 for this question. I have exactly the same problem. The reason why I want to get rid of these warnings is that I want to see no warnings except in the cases that are actually relevant. If I keep seeing irrelevant warnings, I will tend to ignore them and probably fail to see the relevant ones.

Unfortunately, I can't seem to get rid of them. The platform is win32, I tried each of these lines (separately, not all at one), to no avail:

@
QMAKE_CXXFLAGS += -wd4100
QMAKE_CXXFLAGS += -Wno-unused-parameter
QMAKE_CXXFLAGS += /wd4100 /wd4101 /wd4102 /wd4189 /wd4996
QMAKE_CXXFLAGS_WARN_ON = -Wall -Wno-unused-parameter
QMAKE_CXXFLAGS += -wd4100 -wd4101 -wd4102 -wd4189 -wd4996
@

With the last line above, the compile output looks like this:

@
cl -c -nologo -Zm200 -Zc:wchar_t -FS -wd4100 -wd4101 -wd4102 -wd4189 -wd4996 -Zi -MDd -GR -W3 -w34100 -w34189 -EHsc /Fddebug\FirstQtTest.pdb -DUNICODE -DWIN32

more defines and includes follow here

@

There is no -Wall argument in my case, still it doesn't work. Any ideas?

mabeghin

@tjrob said:

SOLUTION: In the .pro file:
QMAKE_CXXFLAGS_WARN_ON = -Wall -Wno-unused-parameter

This sets the flags used when warn_on appears in CONFIG (the default). Now they are in the right order.

This one worked for me ! Thanks a lot ! Removing particular warnings that are generated by external libraries is very useful to still be able to see important ones. When possible I prefer to add specific pragmas when including headers but it's not always possible