On 4/26/21 12:17 PM, Patrick Palka wrote:
When substituting into the arguments of a base initializer pack expansion, tsubst_initializer_list uses a dummy EXPR_PACK_EXPANSION in order to expand an initializer such as Bases(args)... into Bases#{0}(args#{0}) and so on. But when an argument inside the base initializer is itself an pack expansion, e.g. in Bases(args...)..., the argument is already an EXPR_PACK_EXPANSION so we don't need to wrap it, it's also is independent from the outer one for Bases, so we need to multiplicatively append all expanded arguments onto the argument list for each expanded base.Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk?
OK.
gcc/cp/ChangeLog: PR c++/88580 * pt.c (tsubst_initializer_list): Correctly handle the case where an argument inside a base initializer pack expansion is itself a pack expansion. gcc/testsuite/ChangeLog: PR c++/88580 * g++.dg/cpp0x/variadic182.C: New test. --- gcc/cp/pt.c | 28 +++++++++++++++++------- gcc/testsuite/g++.dg/cpp0x/variadic182.C | 18 +++++++++++++++ 2 files changed, 38 insertions(+), 8 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic182.C diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 8c3c814ce55..eaf46659f85 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -26389,9 +26389,16 @@ tsubst_initializer_list (tree t, tree argvec) tree expanded_exprs;/* Expand the argument. */- SET_PACK_EXPANSION_PATTERN (expr, TREE_VALUE (arg)); + tree value; + if (TREE_CODE (TREE_VALUE (arg)) == EXPR_PACK_EXPANSION) + value = TREE_VALUE (arg); + else + { + value = expr; + SET_PACK_EXPANSION_PATTERN (value, TREE_VALUE (arg)); + } expanded_exprs - = tsubst_pack_expansion (expr, argvec, + = tsubst_pack_expansion (value, argvec, tf_warning_or_error, NULL_TREE); if (expanded_exprs == error_mark_node) @@ -26400,12 +26407,17 @@ tsubst_initializer_list (tree t, tree argvec) /* Prepend each of the expanded expressions to the corresponding TREE_LIST in EXPANDED_ARGUMENTS. */ for (i = 0; i < len; i++) - { - TREE_VEC_ELT (expanded_arguments, i) = - tree_cons (NULL_TREE, - TREE_VEC_ELT (expanded_exprs, i), - TREE_VEC_ELT (expanded_arguments, i)); - } + if (TREE_CODE (TREE_VALUE (arg)) == EXPR_PACK_EXPANSION) + for (int j = 0; j < TREE_VEC_LENGTH (expanded_exprs); j++) + TREE_VEC_ELT (expanded_arguments, i) + = tree_cons (NULL_TREE, + TREE_VEC_ELT (expanded_exprs, j), + TREE_VEC_ELT (expanded_arguments, i)); + else + TREE_VEC_ELT (expanded_arguments, i) + = tree_cons (NULL_TREE, + TREE_VEC_ELT (expanded_exprs, i), + TREE_VEC_ELT (expanded_arguments, i)); } in_base_initializer = 0;diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic182.C b/gcc/testsuite/g++.dg/cpp0x/variadic182.Cnew file mode 100644 index 00000000000..078de740e01 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/variadic182.C @@ -0,0 +1,18 @@ +// PR c++/88580 +// { dg-do compile { target c++11 } } + +template <class... Bases> +struct Derived : Bases... { + template <class... Ts> + Derived(Ts... args) : Bases(args, args..., args)... { } +}; + +struct A { }; +struct B { }; +struct C { }; + +struct Base1 { Base1(A, A, B, C, A); }; +struct Base2 { Base2(B, A, B, C, B); }; +struct Base3 { Base3(C, A, B, C, C); }; + +Derived<Base1, Base2, Base3> d(A{}, B{}, C{});
