On 02/25/2014 04:27 PM, Jason Merrill wrote:
Getting the reference binding rules for C++11 right (in the standard) has taken quite a few iterations. I'm pretty happy with the latest wording, which deals with user-defined conversions by recursing on the result of the conversion. This patch implements those rules.
The earlier patch broke Firefox and was reverted; this patch avoids that regression.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 17d24bce33f71316e2b1f0a4a96deb29d09de0be Author: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4> Date: Tue Feb 25 21:27:51 2014 +0000 DR 1571 * call.c (reference_binding): Recurse on user-defined conversion. diff --git a/gcc/cp/call.c b/gcc/cp/call.c index fbd2f83..8c55c32 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -1684,20 +1684,30 @@ reference_binding (tree rto, tree rfrom, tree expr, bool c_cast_p, int flags, if (!conv) return NULL; + if (conv->user_conv_p) + { + /* If initializing the temporary used a conversion function, + recalculate the second conversion sequence. */ + for (conversion *t = conv; t; t = next_conversion (t)) + if (t->kind == ck_user + && DECL_CONV_FN_P (t->cand->fn)) + { + tree ftype = TREE_TYPE (TREE_TYPE (t->cand->fn)); + int sflags = (flags|LOOKUP_NO_CONVERSION)&~LOOKUP_NO_TEMP_BIND; + conversion *new_second + = reference_binding (rto, ftype, NULL_TREE, c_cast_p, + sflags, complain); + if (!new_second) + return NULL; + return merge_conversion_sequences (t, new_second); + } + } + conv = build_conv (ck_ref_bind, rto, conv); /* This reference binding, unlike those above, requires the creation of a temporary. */ conv->need_temporary_p = true; - if (TYPE_REF_IS_RVALUE (rto)) - { - conv->rvaluedness_matches_p = 1; - /* In the second case, if the reference is an rvalue reference and - the second standard conversion sequence of the user-defined - conversion sequence includes an lvalue-to-rvalue conversion, the - program is ill-formed. */ - if (conv->user_conv_p && next_conversion (conv)->kind == ck_rvalue) - conv->bad_p = 1; - } + conv->rvaluedness_matches_p = TYPE_REF_IS_RVALUE (rto); return conv; } diff --git a/gcc/testsuite/g++.dg/cpp0x/overload3.C b/gcc/testsuite/g++.dg/cpp0x/overload3.C index 2d95783..0eecabd 100644 --- a/gcc/testsuite/g++.dg/cpp0x/overload3.C +++ b/gcc/testsuite/g++.dg/cpp0x/overload3.C @@ -13,5 +13,5 @@ struct wrap int main() { wrap w; - f(w); // { dg-error "lvalue" } + f(w); // { dg-error "" } } diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-init1.C b/gcc/testsuite/g++.dg/cpp0x/rv-init1.C new file mode 100644 index 0000000..2e8d4f7 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/rv-init1.C @@ -0,0 +1,26 @@ +// Core DR 1604/1571/1572 +// { dg-require-effective-target c++11 } + +struct Banana { }; +struct Enigma { operator const Banana(); }; +struct Doof { operator Banana&(); }; +void enigmatic() { + typedef const Banana ConstBanana; + Banana &&banana1 = ConstBanana(); // { dg-error "" } + Banana &&banana2 = Enigma(); // { dg-error "" } + Banana &&banana3 = Doof(); // { dg-error "" } +} + +class A { +public: + operator volatile int &(); +}; +A a; + +const int & ir1a = a.operator volatile int&(); // { dg-error "" } +const int & ir2a = a; // { dg-error "" } + +struct X { + operator int&(); +} x; +int&& rri2 = X(); // { dg-error "" }