... and use them consistently instead of naked qWarning()s. As a drive-by, fix the warnings we generate on failures, which all-too-often was "invalid data". Code for minimal size by DRYing what the compiler can't, and using Q_DECL_COLD_FUNCTION to avoid excessive inlining. Left the one qWarning() in qCompress(), for now, because that would have changed the return value from an empty to a null byte array. Move invalidCompressedData() to where the others are defined, too, because it's required by a follow-up commit. Pick-to: 6.4 6.3 6.2 Task-number: QTBUG-104972 Change-Id: Ia43aa315960b06530e98c1d7525ccf0e7f71bb5c Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>