C++98 warnings after update to Qt 5.14 (MSVS2017)

Bertha 。 2023-06-28 08:50 9阅读 0赞

# C++98 warnings after update to Qt 5.14 (MSVS2017) #

## Question ##

After updating Qt to 5.15, I'm getting "incompatible with C++98" errors in ALL the places. I'm using CONFIG += c++11 (was using c++17 before but today I've learnt it apparently does nothing and the correct was is c++11 but the errors are there for both) and MSVS2019 (Qt MSVS2017 but it's compatible).

Something changed? My app builds and runs the same, it's just that I'm getting all these warnings in every file, even Q\_OBJECT macro is "unsupported" because of "nullptr" used there so you can imagine... I don't want to suppress all the warnings, I just want to get back to pre-upgrade state.

## Solution ##

That's because the diagnostic configuration being set to "Checks for questionable constructs \[build-in\]" consists in "-Wall -Wextra", which also includes warnings that warn you about code that is not compatible with C++98, and C++11 is not compatible.

Please go to "Tools -> Options -> C++ -> Code Model" and select the "Build system warnings \[build-in\]", which will take the diagnostics from the build system. Alternatively you can make your own diagnostic configuration.

Edit: As it turns out, the --driver-mode=cl configuration of clang is enabling -Wc++98-compat warning for MSVC. In GNU mode the warning is not enabled. By adding -Wno-c++98-compat besides -Wall -Wextra it made all the warnings go away.

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