This was first reported in [1] but I could not find any bug report. The following code compiled with `gcc -Wall -std=c++17`: template <bool... B> bool foo () { return ((B && true) || ...); } int main () { foo<true, false, false, true> (); } produces this warning: t.cxx:7:38: required from here t.cxx:3:18: warning: suggest parentheses around '&&' within '||' [-Wparentheses] return ((B && true) || ...); ~~~^~~~~~~~ t.cxx:3:18: warning: suggest parentheses around '&&' within '||' [-Wparentheses] Reproducible with any recent gcc version including gcc-trunk-20200406 (on godbolt). [1] http://gcc.1065356.n8.nabble.com/Logical-operator-inside-fold-expression-strange-warning-td1627740.html
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>: https://gcc.gnu.org/g:5bdd4c5d3fc9c143e8edea3b10828e4b75d7a385 commit r10-7830-g5bdd4c5d3fc9c143e8edea3b10828e4b75d7a385 Author: Marek Polacek <polacek@redhat.com> Date: Sun Apr 19 12:12:01 2020 -0400 c++: Fix bogus -Wparentheses warning with fold-expression [PR94505] We issue bogus -Wparentheses warnings (3 of them!) for this fold expression: ((B && true) || ...) Firstly, issuing a warning for a compiler-generated expression is wrong and secondly, B && true must be wrapped in ( ) otherwise you'll get error: binary expression in operand of fold-expression. PR c++/94505 - bogus -Wparentheses warning with fold-expression. * pt.c (fold_expression): Add warning_sentinel for -Wparentheses before calling build_x_binary_op. * g++.dg/cpp1z/fold11.C: New test.
The releases/gcc-9 branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>: https://gcc.gnu.org/g:83eeda5f004c3b9cbeccd3da1c3fe58b3015e55f commit r9-8518-g83eeda5f004c3b9cbeccd3da1c3fe58b3015e55f Author: Marek Polacek <polacek@redhat.com> Date: Mon Apr 20 15:43:49 2020 -0400 c++: Fix bogus -Wparentheses warning with fold-expression [PR94505] We issue bogus -Wparentheses warnings (3 of them!) for this fold expression: ((B && true) || ...) Firstly, issuing a warning for a compiler-generated expression is wrong and secondly, B && true must be wrapped in ( ) otherwise you'll get error: binary expression in operand of fold-expression. PR c++/94505 - bogus -Wparentheses warning with fold-expression. * pt.c (fold_expression): Add warning_sentinel for -Wparentheses before calling build_x_binary_op. * g++.dg/cpp1z/fold11.C: New test.
Fixed in GCC 9.4 and 10.