#include <iostream> // the deprecated attribute is ignored by the compiler for the BAD template. It works for GOOD. template <bool b> struct GOOD {static constexpr int value=1012;}; template <> struct [[deprecated("GOODT")]] GOOD<true> {static constexpr int value=1099;}; template <> struct GOOD<false>{static constexpr int value=1000;}; template <bool b, long i> struct BAD {static constexpr int value=i;}; template <long i > struct [[deprecated("BADT")]] BAD<true, i> {static constexpr int value=100+i;}; template <long i > struct BAD<false, i>{static constexpr int value=-100+i;}; int main () { std::cout<<"GOODCLASS "<<GOOD<true>::value <<':'<<GOOD<false>::value <<std::endl; GOOD<true> goodt; GOOD<false> goodf; std::cout<<"GOODOBJECT "<<goodt.value<<':'<<goodf.value<<std::endl <<std::endl; std::cout<<"BADCLASS "<< BAD<true,4>::value<<':'<<BAD <false,8>::value <<std::endl; BAD<true,4> badt4; BAD<false,8> badf8; std::cout<<"BADOBJECT "<<badt4.value <<':'<<badf8.value <<std::endl <<std::endl; return 0; } /* D:\>g++ -v Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=D:/mingw9.1MCF/bin/../lib/gcc/x86_64-w64-mingw32/9.1.1/lto-wrapper.exe Target: x86_64-w64-mingw32 Configured with: ../gcc/configure --prefix=/mingw64 --with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32 --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --with-native-system-header-dir=/mingw64/x86_64-w64-mingw32/include --libexecdir=/mingw64/lib --enable-bootstrap --with-arch=x86-64 --with-tune=nocona --enable-languages=c,lto,c++ --enable-shared --enable-static --enable-threads=mcf --enable-graphite --enable-fully-dynamic-string --enable-libstdcxx-time=yes --disable-libstdcxx-pch --disable-libstdcxx-debug --enable-libstdcxx-filesystem-ts=yes --disable-isl-version-check --enable-lto --enable-libgomp --disable-multilib --enable-checking=release --disable-rpath --disable-win32-registry --enable-nls --disable-werror --disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw64 --with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64 --with-pkgversion='gcc-9-branch HEAD with MCF thread model, built by LH_Mouse.' --with-bugurl=https://gcc-mcf.lhmouse.com/ --with-gnu-as --with-gnu-ld --disable-tls --enable-plugin Thread model: mcf gcc version 9.1.1 20190506 (gcc-9-branch HEAD with MCF thread model, built by LH_Mouse.) D:\>g++ -std=c++2a -Wall -Wextra deprecatedError.cpp deprecatedError.cpp: In function 'int main()': deprecatedError.cpp:18:14: warning: 'GOOD' is deprecated: GOODT [-Wdeprecated-declarations] 18 | GOOD<true> goodt; | ^~~~~ deprecatedError.cpp:6:50: note: declared here 6 | template <> struct [[deprecated("GOODT")]] GOOD<true> {static constexpr int value=1099;}; | ^~~~~~~~~~ D:\>a GOODCLASS 1099:1000 GOODOBJECT 1099:1000 BADCLASS 104:-92 BADOBJECT 104:-92 D:\> Same result for $ g++ -v Using built-in specs. COLLECT_GCC=D:\msys64\mingw64\bin\g++.exe COLLECT_LTO_WRAPPER=D:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.3.0/lto-wrapper.exe Target: x86_64-w64-mingw32 Configured with: ../gcc-8.3.0/configure --prefix=/mingw64 --with-local-prefix=/mingw64/local --build=x86_64-w64-mingw32 --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --with-native-system-header-dir=/mingw64/x86_64-w64-mingw32/include --libexecdir=/mingw64/lib --enable-bootstrap --with-arch=x86-64 --with-tune=generic --enable-languages=ada,c,lto,c++,objc,obj-c++,fortran --enable-shared --enable-static --enable-libatomic --enable-threads=posix --enable-graphite --enable-fully-dynamic-string --enable-libstdcxx-filesystem-ts=yes --enable-libstdcxx-time=yes --disable-libstdcxx-pch --disable-libstdcxx-debug --disable-isl-version-check --enable-lto --enable-libgomp --disable-multilib --enable-checking=release --disable-rpath --disable-win32-registry --disable-nls --disable-werror --disable-symvers --with-libiconv --with-system-zlib --with-gmp=/mingw64 --with-mpfr=/mingw64 --with-mpc=/mingw64 --with-isl=/mingw64 --with-pkgversion='Rev2, Built by MSYS2 project' --with-bugurl=https://sourceforge.net/projects/msys2 --with-gnu-as --with-gnu-ld Thread model: posix gcc version 8.3.0 (Rev2, Built by MSYS2 project) peter@DESKTOP-U70S6AV MSYS /d $ */