This testcase revealed that we were using PACK_EXPANSION_EXTRA_ARGS a lot more than necessary; use_pack_expansion_extra_args_p meant to use it in the case of corresponding arguments in different argument packs differing in whether they are pack expansions, but it was mistakenly also returning true for the case of a single argument pack containing both expansion and non-expansion elements.
Surprisingly, just disabling that didn't lead to any regressions in the testsuite; it seems other changes have prevented us getting to this point for code that used to exercise it. So this patch limits the check to arguments in the same position in the packs, and asserts that we never actually see a mismatch. PR c++/86355 gcc/cp/ChangeLog: * pt.c (use_pack_expansion_extra_args_p): Don't compare args from the same argument pack. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/alias-decl-variadic2.C: New test. --- gcc/cp/pt.c | 7 +++++-- gcc/testsuite/g++.dg/cpp0x/alias-decl-variadic2.C | 13 +++++++++++++ 2 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-variadic2.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index e4950aa448a..bb22d685617 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -12422,9 +12422,9 @@ use_pack_expansion_extra_args_p (tree parm_packs, return false; } - bool has_expansion_arg = false; for (int i = 0 ; i < arg_pack_len; ++i) { + bool has_expansion_arg = false; bool has_non_expansion_arg = false; for (tree parm_pack = parm_packs; parm_pack; @@ -12444,7 +12444,10 @@ use_pack_expansion_extra_args_p (tree parm_packs, } if (has_expansion_arg && has_non_expansion_arg) - return true; + { + gcc_checking_assert (false); + return true; + } } return false; } diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-variadic2.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-variadic2.C new file mode 100644 index 00000000000..4299c7e88dc --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-variadic2.C @@ -0,0 +1,13 @@ +// PR c++/86355 +// { dg-do compile { target c++11 } } + +template <int...> struct integral_constant { + static const int value = 1; +}; +template <class... T> using mp_all = integral_constant<T::value...>; +template <class... T> using check2 = mp_all<mp_all<T..., integral_constant<0>>>; +check2<> x; + +template <class T, class U> struct assert_same; +template <class T> struct assert_same<T,T> { }; +assert_same<decltype(x),integral_constant<1>> a; base-commit: 9b94785dedb08b006419bec1a402614d9241317a -- 2.27.0