Qt Creator displaying warnings related to C++98

[GregB]

I'm running Qt Creator 15.0.1 on Windows, and I'm getting warnings about incompatibilites with C++98. This is appearing as annotations in code editor.

I've added the following to the .pro file, but it didn't change any behavior

CONFIG -= c++98
CONFIG += c++11
CONFIG += c++17

How can I get the clang code model to ignore C++98 issues?

[aha_1980]

@GregB You are currently adding both C++11 and C++17 - please choose one of them. If you use an older Qt and therefore qmake version, you might need to replace C++17 with C++1z

Also, I doubt that CONFIG -= c++98 has any meaning, see https://doc.qt.io/qt-6/qmake-variable-reference.html#config for known variables.

If you still encounter problems, please share the code you are getting warnings with.

Regards

[GregB]

I changed the .pro file to only contain the c++17. The warnings that I'm getting are within Qt Creator, not from the build process. Some example warnings are below:

M:\nidb\src\nidb\modulePipeline.cpp:300: warning: 'auto' type specifier is incompatible with C++98
M:\nidb\src\nidb\modulePipeline.cpp:300: warning: If initialization statements are incompatible with C++ standards before C++17
M:\nidb\src\nidb\modulePipeline.cpp:1377: warning: Initialization of initializer_list object is incompatible with C++98
M:\nidb\src\nidb\modulePipeline.cpp:1867: warning: 'auto' type specifier is incompatible with C++98
M:\nidb\src\nidb\modulePipeline.cpp:1867: warning: If initialization statements are incompatible with C++ standards before C++17
M:\nidb\src\nidb\modulePipeline.cpp:2188: warning: Universal character name referring to a control character is incompatible with C++98

[aha_1980]

@GregB could you also share the relevant code lines?

[GregB]

Line 300

foreach (int sid, studyids) {

Line 1377

QStringList bidsflags = { "BIDS_SUBJECTDIR_UID", "BIDS_STUDYDIR_STUDYNUM" };

Line 1867

foreach (QString group, groups) {

I'm not sure that the code is invalid? This code builds without warnings or error. The only issue is the warnings within Qt Creator generated by clangd within the editor. I recently upgraded my computer and reinstalled Qt Creator, and that's when I started getting the warnings. I was using 15.0.1 before, and 15.0.1 now. I must have had a setting turned off on my previous computer related to clangd, but I don't know what the setting is.

[JonB]

@GregB
Up to you, but you could change foreach() to for ( : ), and I would guess remove the = in the middle one? Not that you have to, but these are newer constructs and I guess it's moaning about the older ones?

[aha_1980]

@GregB Thanks. Looking at the foreach source code there is indeed a line for (auto name = QtPrivate::qMakeForeachContainer(container); name.i != name.e; ++name.i) which is valid C++11 and higher code.

So I think for some reason the code model does not pick up the C++17 specifier. Can you try a minimal "Hello World" style example?

@JonB Be careful with such suggestions. Changing foreach() to range-based for requires a studies with diploma exam ;)

Regards

[JonB]

@aha_1980 said in Qt Creator displaying warnings related to C++98:

@JonB Be careful with such suggestions. Changing foreach() to range-based for requires a studies with diploma exam ;)

If you say so! I only know that I use for instead of foreach (at least in similar cases to what the OP shows above, an int and a QString and their lists) and never had any issues?

[aha_1980]

@JonB: You think you don't have any issues before you read the post Goodbye Q_FOREACH! I mentioned.

Regards

[JonB]

@aha_1980
But just to round off, I thought there are no issues for the specific int-in-list and QString-in-QStringList OP's cases as shown, or are there?

[aha_1980]

@JonB: not for the int and the QString , but probably for the corresponding lists. But for the details, you will have to read the mentioned post.

[GregB]

Thanks for the comments. So I don't think there's anything wrong with the code itself. It seems to be a configuration with Qt Creator and clangd that is ignoring the c++17 specification in the .pro file.

I found a previous post about this issue, and how they fixed it: https://forum.qt.io/topic/109856/incompatible-with-c-98-warnings-since-qt-creater-update/3

But that post is 5 years old, and none of the options they used to fix the issue exist in in the current Qt Creator.

[f222]

I might be digging up the post but I encountered the same issue because I had spaces in my compiler flags.

I am using clang-cl and in my .pro file I added includes using imsvc to avoid warning on those files like so:

QMAKE_CXXFLAGS += /imsvc\"C:/path with spaces /to/include/folder\"

Using \ before the quotes and / as path delimiter allows the code to compile as expected but it doesn't prevent the code model from being broken.

If I go to Tools->Debug Qt Creator -> Inspect C++ code model , under Project Parts tab in the General tab and look at the compiler flags you can see that it will split the path on the spaces and consider the parts of the path as separate flags:

(Example shown on Qt5 but it's the same with Qt 6)