Hi! When backporting the PR61414 fix to 8.4, I've noticed that the caching of prec is actually broken, as it would fail to actually store the computed precision into the hash_map's value and so next time we'd think the enum needs 0 bits.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux and committed to trunk, 9.3 and 8.4. 2020-02-14 Jakub Jelinek <ja...@redhat.com> PR c++/61414 * class.c (enum_min_precision): Change prec type from int to int &. * g++.dg/cpp0x/enum39.C: New test. --- gcc/cp/class.c.jj 2020-02-12 11:44:18.423371637 +0100 +++ gcc/cp/class.c 2020-02-14 14:33:41.842057349 +0100 @@ -3289,7 +3289,7 @@ enum_min_precision (tree type) enum_to_min_precision = hash_map<tree, int>::create_ggc (37); bool existed; - int prec = enum_to_min_precision->get_or_insert (type, &existed); + int &prec = enum_to_min_precision->get_or_insert (type, &existed); if (existed) return prec; --- gcc/testsuite/g++.dg/cpp0x/enum39.C.jj 2020-02-14 14:30:26.489972394 +0100 +++ gcc/testsuite/g++.dg/cpp0x/enum39.C 2020-02-14 14:30:22.530031482 +0100 @@ -0,0 +1,15 @@ +// PR c++/61414 +// { dg-do compile { target c++11 } } + +enum class E { E0 = -4, E1 = 3 }; +enum F : unsigned { F0 = 0, F1 = 15 }; + +struct S +{ + E a : 2; // { dg-warning "'S::a' is too small to hold all values of 'enum class E'" } + E b : 2; // { dg-warning "'S::b' is too small to hold all values of 'enum class E'" } + E c : 3; // { dg-bogus "'S::c' is too small to hold all values of 'enum class E'" } + F d : 3; // { dg-warning "'S::d' is too small to hold all values of 'enum F'" } + F e : 3; // { dg-warning "'S::e' is too small to hold all values of 'enum F'" } + F f : 4; // { dg-bogus "'S::f' is too small to hold all values of 'enum F'" } +}; Jakub