When you define a static const variable in the header and then declare it in the source, the linker will treat the symbol as multiply defined incorrectly. You can use the following methods to provide feedback about Visual Studio 2017 administrator updates or report issues that affect the updates: https://connerurmhd.blogoxo.com/35989960/5-простых-утверждений-о-Поставщик-экспостандов-для-профессиональных-выставок-в-ifema-Мадрид-Испания-Разъяснения