On Fri, 10 Nov 2023, Jason Merrill wrote: > On 11/10/23 12:25, Patrick Palka wrote: > > On Thu, 9 Nov 2023, Jason Merrill wrote: > > > > > On 11/7/23 10:08, Patrick Palka wrote: > > > > bootstrapped and regtested on x86_64-pc-linxu-gnu, does this look OK for > > > > trunk? > > > > > > > > -- >8 -- > > > > > > > > In the COMPOUND_EXPR case of tsubst_expr, we were redundantly clearing > > > > the tf_decltype flag when substituting the LHS and also neglecting to > > > > propagate it when substituting the RHS. This patch corrects this flag > > > > manipulation, which allows us to accept the below testcase. > > > > > > > > gcc/cp/ChangeLog: > > > > > > > > * pt.cc (tsubst_expr) <case COMPOUND_EXPR>: Don't redundantly > > > > clear tf_decltype when substituting the LHS. Propagate > > > > tf_decltype when substituting the RHS. > > > > > > > > gcc/testsuite/ChangeLog: > > > > > > > > * g++.dg/cpp0x/decltype-call7.C: New test. > > > > --- > > > > gcc/cp/pt.cc | 9 ++++----- > > > > gcc/testsuite/g++.dg/cpp0x/decltype-call7.C | 9 +++++++++ > > > > 2 files changed, 13 insertions(+), 5 deletions(-) > > > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype-call7.C > > > > > > > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > > > > index 521749df525..5f879287a58 100644 > > > > --- a/gcc/cp/pt.cc > > > > +++ b/gcc/cp/pt.cc > > > > @@ -20382,11 +20382,10 @@ tsubst_expr (tree t, tree args, tsubst_flags_t > > > > complain, tree in_decl) > > > > case COMPOUND_EXPR: > > > > { > > > > - tree op0 = tsubst_expr (TREE_OPERAND (t, 0), args, > > > > - complain & ~tf_decltype, in_decl); > > > > - RETURN (build_x_compound_expr (EXPR_LOCATION (t), > > > > - op0, > > > > - RECUR (TREE_OPERAND (t, 1)), > > > > + tree op0 = RECUR (TREE_OPERAND (t, 0)); > > > > + tree op1 = tsubst_expr (TREE_OPERAND (t, 1), args, > > > > + complain|decltype_flag, in_decl); > > > > + RETURN (build_x_compound_expr (EXPR_LOCATION (t), op0, op1, > > > > templated_operator_saved_lookups > > > > (t), > > > > complain|decltype_flag)); > > > > > > Hmm, passing decltype_flag to both op1 and the , is concerning. Can you > > > add a > > > test with overloaded operator, where the RHS is a class with a destructor? > > > > I'm not sure if this is what you had in mind, but indeed with this patch > > we reject the following with an error outside the immediate context: > > > > struct B { ~B() = delete; }; > > template<class T> B f(); > > > > void operator,(int, const B&); > > > > template<class T> decltype(42, f<T>()) g(int) = delete; // #1 > > template<class T> void g(...); // #2 > > > > int main() { > > g<B>(0); // should select #2 > > } > > > > gcc/testsuite/g++.dg/cpp0x/decltype-call8.C: In substitution of > > ‘template<class T> decltype ((42, f<T>())) g(int) [with T = B]’: > > gcc/testsuite/g++.dg/cpp0x/decltype-call8.C:12:7: required from here > > 12 | g<B>(0); > > | ~~~~^~~ > > gcc/testsuite/g++.dg/cpp0x/decltype-call8.C:8:30: error: use of deleted > > function ‘B::~B()’ > > 8 | template<class T> decltype(42, f<T>()) g(int) = delete; // #1 > > | ~~^~~~~~~~ > > gcc/testsuite/g++.dg/cpp0x/decltype-call8.C:3:12: note: declared here > > 3 | struct B { ~B() = delete; }; > > | ^ > > > > Ultimately because unary_complex_lvalue isn't SFINAE-enabled. > > Please elaborate; my understanding is that unary_complex_lvalue is supposed to > be a semantically neutral transformation.
Since tf_decltype is now also set when substituting op1 i.e. f<T>(), substitution yields a bare CALL_EXPR with no temporary materialization. The problematic unary_complex_lvalue call happens when binding the reference parameter 'const B&' to this bare CALL_EXPR. We take its address via cp_build_addr_expr, which tries unary_complex_lvalue. The CALL_EXPR handling in unary_complex_lvalue in turn materializes a temporary for the call, which fails as expected due to the destructor but also issues the unexpected error since unary_complex_lvalue unconditionally uses tf_warning_or_error. So in short the CALL_EXPR handling in unary_complex_lvalue seems to assume the requirements of temporary materialization have already been checked. > > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > > index 4f2cb2cd402..277c81412b9 100644 > > --- a/gcc/cp/pt.cc > > +++ b/gcc/cp/pt.cc > > @@ -20386,7 +20386,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t > > complain, tree in_decl) > > complain|decltype_flag, in_decl); > > RETURN (build_x_compound_expr (EXPR_LOCATION (t), op0, op1, > > templated_operator_saved_lookups (t), > > - complain|decltype_flag)); > > + complain)); > > This looks like it will break if the operator, returns a class with a deleted > destructor. Ah sorry about that, this hunk wasn't intended to be part of the diff. Here's a full tested patch for consideration. The additional build_const_cast_1 call in cp_build_c_cast is needed to preserve the last four errors in gcc/testsuite/g++.dg/tree-ssa/pr20280.C (which get indirectly issued from unary_complex_lvalue). -- >8 -- Subject: [PATCH] c++: make unary_complex_lvalue SFINAE-enabled gcc/cp/ChangeLog: * class.cc (build_simple_base_path): Adjust call to unary_complex_value. * cp-tree.h (unary_complex_lvalue): Add complain parameter. * typeck.cc (build_class_member_access_expr): Adjust call to unary_complex_lvalue. (cp_build_addr_expr_1): Likewise. (cp_build_unary_op): Likewise. (unary_complex_lvalue): Add complain parameter and propagate it. Propagate error_mark_node result from build_cplus_new. (cp_build_c_cast): If we're committed to a const_cast and the result is erroneous, call build_const_cast_1 a second time to issue errors. --- gcc/cp/class.cc | 2 +- gcc/cp/cp-tree.h | 2 +- gcc/cp/typeck.cc | 27 +++++++++++++++++---------- 3 files changed, 19 insertions(+), 12 deletions(-) diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc index 9d4d95f85bf..58c45542793 100644 --- a/gcc/cp/class.cc +++ b/gcc/cp/class.cc @@ -556,7 +556,7 @@ build_simple_base_path (tree expr, tree binfo) into `(*(a ? &b : &c)).x', and so on. A COND_EXPR is only an lvalue in the front end; only _DECLs and _REFs are lvalues in the back end. */ - temp = unary_complex_lvalue (ADDR_EXPR, expr); + temp = unary_complex_lvalue (ADDR_EXPR, expr, tf_warning_or_error); if (temp) expr = cp_build_fold_indirect_ref (temp); diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 1fa710d7154..d826afcdb5c 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -8130,7 +8130,7 @@ extern tree cp_build_addr_expr (tree, tsubst_flags_t); extern tree cp_build_unary_op (enum tree_code, tree, bool, tsubst_flags_t); extern tree genericize_compound_lvalue (tree); -extern tree unary_complex_lvalue (enum tree_code, tree); +extern tree unary_complex_lvalue (enum tree_code, tree, tsubst_flags_t); extern tree build_x_conditional_expr (location_t, tree, tree, tree, tsubst_flags_t); extern tree build_x_compound_expr_from_list (tree, expr_list_kind, diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc index 49afbd8fb5e..be6667c192e 100644 --- a/gcc/cp/typeck.cc +++ b/gcc/cp/typeck.cc @@ -2888,7 +2888,7 @@ build_class_member_access_expr (cp_expr object, tree member, /* Transform `(a, b).x' into `(*(a, &b)).x', `(a ? b : c).x' into `(*(a ? &b : &c)).x', and so on. A COND_EXPR is only an lvalue in the front end; only _DECLs and _REFs are lvalues in the back end. */ - if (tree temp = unary_complex_lvalue (ADDR_EXPR, object)) + if (tree temp = unary_complex_lvalue (ADDR_EXPR, object, complain)) { temp = cp_build_fold_indirect_ref (temp); if (!lvalue_p (object) && lvalue_p (temp)) @@ -7118,7 +7118,7 @@ cp_build_addr_expr_1 (tree arg, bool strict_lvalue, tsubst_flags_t complain) /* Handle complex lvalues (when permitted) by reduction to simpler cases. */ - val = unary_complex_lvalue (ADDR_EXPR, arg); + val = unary_complex_lvalue (ADDR_EXPR, arg, complain); if (val != 0) return val; @@ -7411,7 +7411,7 @@ cp_build_unary_op (enum tree_code code, tree xarg, bool noconvert, /* Handle complex lvalues (when permitted) by reduction to simpler cases. */ - val = unary_complex_lvalue (code, arg); + val = unary_complex_lvalue (code, arg, complain); if (val != 0) goto return_build_unary_op; @@ -7657,7 +7657,7 @@ genericize_compound_lvalue (tree lvalue) NULL_TREE. */ tree -unary_complex_lvalue (enum tree_code code, tree arg) +unary_complex_lvalue (enum tree_code code, tree arg, tsubst_flags_t complain) { /* Inside a template, making these kinds of adjustments is pointless; we are only concerned with the type of the @@ -7669,7 +7669,7 @@ unary_complex_lvalue (enum tree_code code, tree arg) if (TREE_CODE (arg) == COMPOUND_EXPR) { tree real_result = cp_build_unary_op (code, TREE_OPERAND (arg, 1), false, - tf_warning_or_error); + complain); return build2 (COMPOUND_EXPR, TREE_TYPE (real_result), TREE_OPERAND (arg, 0), real_result); } @@ -7677,13 +7677,14 @@ unary_complex_lvalue (enum tree_code code, tree arg) /* Handle (a ? b : c) used as an "lvalue". */ if (TREE_CODE (arg) == COND_EXPR || TREE_CODE (arg) == MIN_EXPR || TREE_CODE (arg) == MAX_EXPR) - return rationalize_conditional_expr (code, arg, tf_warning_or_error); + return rationalize_conditional_expr (code, arg, complain); /* Handle (a = b), (++a), and (--a) used as an "lvalue". */ if (TREE_CODE (arg) == MODIFY_EXPR || TREE_CODE (arg) == PREINCREMENT_EXPR || TREE_CODE (arg) == PREDECREMENT_EXPR) - return unary_complex_lvalue (code, genericize_compound_lvalue (arg)); + return unary_complex_lvalue (code, genericize_compound_lvalue (arg), + complain); if (code != ADDR_EXPR) return NULL_TREE; @@ -7693,7 +7694,7 @@ unary_complex_lvalue (enum tree_code code, tree arg) || TREE_CODE (arg) == INIT_EXPR) { tree real_result = cp_build_unary_op (code, TREE_OPERAND (arg, 0), false, - tf_warning_or_error); + complain); arg = build2 (COMPOUND_EXPR, TREE_TYPE (real_result), arg, real_result); suppress_warning (arg /* What warning? */); @@ -7717,7 +7718,11 @@ unary_complex_lvalue (enum tree_code code, tree arg) if (TREE_CODE (arg) == SAVE_EXPR) targ = arg; else - targ = build_cplus_new (TREE_TYPE (arg), arg, tf_warning_or_error); + { + targ = build_cplus_new (TREE_TYPE (arg), arg, complain); + if (targ == error_mark_node) + return error_mark_node; + } return build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (arg)), targ); } @@ -9174,6 +9179,8 @@ cp_build_c_cast (location_t loc, tree type, tree expr, maybe_warn_about_useless_cast (loc, type, value, complain); maybe_warn_about_cast_ignoring_quals (loc, type, complain); } + else if (complain & tf_error) + build_const_cast_1 (loc, type, value, tf_error, &valid_p); return result; } @@ -9209,7 +9216,7 @@ cp_build_c_cast (location_t loc, tree type, tree expr, to succeed. */ if (!same_type_p (non_reference (type), non_reference (result_type))) { - result = build_const_cast_1 (loc, type, result, false, &valid_p); + result = build_const_cast_1 (loc, type, result, tf_none, &valid_p); gcc_assert (valid_p); } return result; -- 2.43.0.rc1