https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84338
Bug ID: 84338 Summary: [8 Regression] sizeof...() returns always 1 in variadic lambda inside a template Product: gcc Version: 8.0.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: benni.buch at gmail dot com Target Milestone: --- template < typename ... T > auto f(T ... i){ [](auto ... i){ // // wrongly true in current trunk // static_assert(sizeof...(i) == 1, ""); static_assert(sizeof...(i) == 2, ""); }(i ...); } int main(){ f(0, 1); } $ g++ -std=c++14 main.cpp main.cpp: In instantiation of 'auto f(T ...) [with T = {int, int}]': main.cpp:11:11: required from here main.cpp:6:36: error: static assertion failed static_assert(sizeof...(i) == 2, ""); ~~~~~~~~~~~~~^~~~ $ g++ --version g++ (GCC) 8.0.1 20180212 (experimental) Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Known to work in GCC 5 and GCC 6: $ g++-6 -std=c++14 main.cpp $ g++-6 --version g++-6 (Ubuntu/Linaro 6.3.0-18ubuntu2~16.04) 6.3.0 20170519 Copyright (C) 2016 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ g++-5 -std=c++14 main.cpp $ g++-5 --version g++-5 (Ubuntu 5.4.1-2ubuntu1~16.04) 5.4.1 20160904 Copyright (C) 2015 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.