On Fri, 10 May 2024, Jason Merrill wrote:
> On 5/9/24 16:23, Patrick Palka wrote:
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > OK for trunk/14? For trunk as a follow-up I can implement the
> > mentionted representation change to use CALL_EXPR instead of
> > MODOP_EXPR for a non-dependent simple assignment expression that
> > resolved to an operator= overload.
> >
> > -- >8 --
> >
> > r14-4111 made us check non-dependent assignment expressions ahead of
> > time, as well as give them a type. Unlike for compound assignment
> > expressions however, if a simple assignment resolves to an operator
> > overload we still represent it as a (typed) MODOP_EXPR instead of a
> > CALL_EXPR to the selected overload. This, I reckoned, was just a
> > pessimization (since we'll have to repeat overload resolution at
> > instantiatiation time) but should be harmless. (And it should be
> > easily fixable by giving cp_build_modify_expr an 'overload' parameter).
> >
> > But it breaks the below testcase ultimately because MODOP_EXPR (of
> > non-reference type) is always treated as an lvalue according to
> > lvalue_kind, which is incorrect for the MODOP_EXPR representing x=42.
> >
> > We can fix this by representing such assignment expressions as CALL_EXPRs
> > matching what that of compound assignments, but that turns out to
> > require some tweaking of our -Wparentheses warning logic which seems
> > unsuitable for backporting.
> >
> > So this patch instead more conservatively fixes this by refining
> > lvalue_kind to consider the type of a (simple) MODOP_EXPR as we
> > already do for COND_EXPR.
> >
> > PR c++/114994
> >
> > gcc/cp/ChangeLog:
> >
> > * tree.cc (lvalue_kind) <case MODOP_EXPR>: Consider the
> > type of a simple assignment expression.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/template/non-dependent32.C: New test.
> > ---
> > gcc/cp/tree.cc | 7 +++++++
> > .../g++.dg/template/non-dependent32.C | 18 ++++++++++++++++++
> > 2 files changed, 25 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/template/non-dependent32.C
> >
> > diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> > index f1a23ffe817..0b97b789aab 100644
> > --- a/gcc/cp/tree.cc
> > +++ b/gcc/cp/tree.cc
> > @@ -275,6 +275,13 @@ lvalue_kind (const_tree ref)
> > /* We expect to see unlowered MODOP_EXPRs only during
> > template processing. */
> > gcc_assert (processing_template_decl);
> > + if (TREE_CODE (TREE_OPERAND (ref, 1)) == NOP_EXPR
> > + && CLASS_TYPE_P (TREE_TYPE (TREE_OPERAND (ref, 0))))
> > + /* As in the COND_EXPR case, but for non-dependent assignment
> > + expressions created by build_x_modify_expr. */
> > + goto default_;
>
> This seems overly specific, I'd think the same thing would apply to += and
> such?
We shouldn't see += etc of class type here since we already represent
those as CALL_EXPR to the selected operator=, but indeed it could
otherwise apply to +=. Like so?
-- >8 --
Subject: [PATCH] c++: lvalueness of non-dependent assignment expr [PR114994]
PR c++/114994
gcc/cp/ChangeLog:
* tree.cc (lvalue_kind) <case MODOP_EXPR>: Consider the
type of a class assignment expression.
gcc/testsuite/ChangeLog:
* g++.dg/template/non-dependent32.C: New test.
---
gcc/cp/tree.cc | 5 ++++-
.../g++.dg/template/non-dependent32.C | 18 ++++++++++++++++++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/template/non-dependent32.C
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index f1a23ffe817..9d37d255d8d 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -275,7 +275,10 @@ lvalue_kind (const_tree ref)
/* We expect to see unlowered MODOP_EXPRs only during
template processing. */
gcc_assert (processing_template_decl);
- return clk_ordinary;
+ if (CLASS_TYPE_P (TREE_TYPE (TREE_OPERAND (ref, 0))))
+ goto default_;
+ else
+ return clk_ordinary;
case MODIFY_EXPR:
case TYPEID_EXPR:
diff --git a/gcc/testsuite/g++.dg/template/non-dependent32.C
b/gcc/testsuite/g++.dg/template/non-dependent32.C
new file mode 100644
index 00000000000..54252c7dfaf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent32.C
@@ -0,0 +1,18 @@
+// PR c++/114994
+// { dg-do compile { target c++11 } }
+
+struct udl_arg {
+ udl_arg operator=(int);
+};
+
+void f(udl_arg&&);
+
+template<class>
+void g() {
+ udl_arg x;
+ f(x=42); // { dg-bogus "cannot bind" }
+}
+
+int main() {
+ g<int>();
+}
--
2.45.0.119.g0f3415f1f8
... and here's the updated patch to make us represent simple class
assignment as CALL_EXPR as well (should the first ptach go in for 14/trunk,
and this second patch for trunk only?):
Subject: [PATCH] c++: lvalueness of non-dependent assignment expr [PR114994]
PR c++/114994
gcc/cp/ChangeLog:
* call.cc (build_new_op): Pass 'overload' to
cp_build_modify_expr.
* cp-tree.h (cp_build_modify_expr): New overload that
takes a tree* out-parameter.
* cvt.cc (cp_get_fndecl_from_callee); Use maybe_get_fns to
handle a templated member function call.
* pt.cc (tsubst_expr) <case CALL_EXPR>: Propagate
OPT_Wparentheses warning suppression to the result.
* typeck.cc (cp_build_modify_expr): Add 'overload'
out-parameter and pass it to build_new_op.
(build_x_modify_expr): Pass 'overload' to cp_build_modify_expr.
gcc/testsuite/ChangeLog:
* g++.dg/template/non-dependent32.C: New test.
---
gcc/cp/call.cc | 2 +-
gcc/cp/cp-tree.h | 3 +++
gcc/cp/cvt.cc | 5 +++--
gcc/cp/pt.cc | 2 ++
gcc/cp/typeck.cc | 18 ++++++++++++++----
.../g++.dg/template/non-dependent32.C | 18 ++++++++++++++++++
6 files changed, 41 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/template/non-dependent32.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index e058da7735f..e3d4cf8949d 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7473,7 +7473,7 @@ build_new_op (const op_location_t &loc, enum tree_code
code, int flags,
switch (code)
{
case MODIFY_EXPR:
- return cp_build_modify_expr (loc, arg1, code2, arg2, complain);
+ return cp_build_modify_expr (loc, arg1, code2, arg2, overload, complain);
case INDIRECT_REF:
return cp_build_indirect_ref (loc, arg1, RO_UNARY_STAR, complain);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index f82446331b3..505c04c6e52 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -8264,6 +8264,9 @@ extern tree cp_build_c_cast
(location_t, tree, tree,
extern cp_expr build_x_modify_expr (location_t, tree,
enum tree_code, tree,
tree, tsubst_flags_t);
+extern tree cp_build_modify_expr (location_t, tree,
+ enum tree_code, tree,
+ tree *, tsubst_flags_t);
extern tree cp_build_modify_expr (location_t, tree,
enum tree_code, tree,
tsubst_flags_t);
diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc
index db086c017e8..2f4c0f88694 100644
--- a/gcc/cp/cvt.cc
+++ b/gcc/cp/cvt.cc
@@ -1015,8 +1015,9 @@ cp_get_fndecl_from_callee (tree fn, bool fold /* = true
*/)
return f;
};
- if (TREE_CODE (fn) == FUNCTION_DECL)
- return fn_or_local_alias (fn);
+ if (tree f = maybe_get_fns (fn))
+ if (TREE_CODE (f) == FUNCTION_DECL)
+ return fn_or_local_alias (f);
tree type = TREE_TYPE (fn);
if (type == NULL_TREE || !INDIRECT_TYPE_P (type))
return NULL_TREE;
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 4b71e199d27..4645040a994 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21093,6 +21093,8 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
if (warning_suppressed_p (t, OPT_Wpessimizing_move))
/* This also suppresses -Wredundant-move. */
suppress_warning (ret, OPT_Wpessimizing_move);
+ if (warning_suppressed_p (t, OPT_Wparentheses))
+ suppress_warning (STRIP_REFERENCE_REF (ret), OPT_Wparentheses);
}
RETURN (ret);
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 5f16994300f..75b696e32e0 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -9421,7 +9421,7 @@ build_modify_expr (location_t location,
tree
cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
- tree rhs, tsubst_flags_t complain)
+ tree rhs, tree *overload, tsubst_flags_t complain)
{
lhs = mark_lvalue_use_nonread (lhs);
@@ -9533,7 +9533,8 @@ cp_build_modify_expr (location_t loc, tree lhs, enum
tree_code modifycode,
rhs = unshare_expr (rhs);
tree op2 = TREE_OPERAND (lhs, 2);
if (TREE_CODE (op2) != THROW_EXPR)
- op2 = cp_build_modify_expr (loc, op2, modifycode, rhs, complain);
+ op2 = cp_build_modify_expr (loc, op2, modifycode, rhs,
+ overload, complain);
tree cond = build_conditional_expr (input_location,
TREE_OPERAND (lhs, 0), op1, op2,
complain);
@@ -9620,7 +9621,7 @@ cp_build_modify_expr (location_t loc, tree lhs, enum
tree_code modifycode,
result = build_new_op (input_location, MODIFY_EXPR,
LOOKUP_NORMAL, lhs, rhs,
make_node (NOP_EXPR), NULL_TREE,
- /*overload=*/NULL, complain);
+ overload, complain);
if (result == NULL_TREE)
return error_mark_node;
goto ret;
@@ -9828,6 +9829,14 @@ cp_build_modify_expr (location_t loc, tree lhs, enum
tree_code modifycode,
return result;
}
+tree
+cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
+ tree rhs, tsubst_flags_t complain)
+{
+ return cp_build_modify_expr (loc, lhs, modifycode, rhs,
+ /*overload=*/nullptr, complain);
+}
+
cp_expr
build_x_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
tree rhs, tree lookups, tsubst_flags_t complain)
@@ -9856,7 +9865,8 @@ build_x_modify_expr (location_t loc, tree lhs, enum
tree_code modifycode,
tree rval;
if (modifycode == NOP_EXPR)
- rval = cp_build_modify_expr (loc, lhs, modifycode, rhs, complain);
+ rval = cp_build_modify_expr (loc, lhs, modifycode, rhs,
+ &overload, complain);
else
rval = build_new_op (loc, MODIFY_EXPR, LOOKUP_NORMAL,
lhs, rhs, op, lookups, &overload, complain);
diff --git a/gcc/testsuite/g++.dg/template/non-dependent32.C
b/gcc/testsuite/g++.dg/template/non-dependent32.C
new file mode 100644
index 00000000000..54252c7dfaf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent32.C
@@ -0,0 +1,18 @@
+// PR c++/114994
+// { dg-do compile { target c++11 } }
+
+struct udl_arg {
+ udl_arg operator=(int);
+};
+
+void f(udl_arg&&);
+
+template<class>
+void g() {
+ udl_arg x;
+ f(x=42); // { dg-bogus "cannot bind" }
+}
+
+int main() {
+ g<int>();
+}
--
2.45.0.119.g0f3415f1f8
