I build using cmake build configuration "Debug" not "RelWithDebInfo".
Building qcoro fails with error "qcoro/qcoro/websockets/qcorowebsocket.cpp: 35:73: error: ‘void QWebSocket::error(QAbstractSocket::SocketError)’ is deprecated: Use errorOccurred instead [-Werror=deprecated-declarations]".
Because "# Only enable strict warnings in debug mode
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall -Wextra -Werror -pedantic")".
OK.
Sorry. I confused ~/kde.6/src/qtwebsockets/src/websockets/qwebsocket.h "error" with /usr/include/x86_64-linux-gnu/qt5/QtCore/qprocess.h "errorOccurred".
I build using cmake build configuration "Debug" not "RelWithDebInfo". Building qcoro fails with error "qcoro/qcoro/websockets/qcorowebsocket.cpp: 35:73: error: ‘void QWebSocket::error(QAbstractSocket::SocketError)’ is deprecated: Use errorOccurred instead [-Werror=deprecated-declarations]". Because "# Only enable strict warnings in debug mode set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall -Wextra -Werror -pedantic")".