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* [gcc r12-6846] c++: value category of compound object expr [PR104173]
@ 2022-01-24 14:17 Patrick Palka
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From: Patrick Palka @ 2022-01-24 14:17 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:2a908f3da07c9e94b8a19e966b45daf0140107e8
commit r12-6846-g2a908f3da07c9e94b8a19e966b45daf0140107e8
Author: Patrick Palka <ppalka@redhat.com>
Date: Mon Jan 24 09:17:35 2022 -0500
c++: value category of compound object expr [PR104173]
Here the call to (the &&-qualified) toLower() is incorrectly rejected
during overload resolution because the object expression is encoded as
an lvalue when it's really a prvalue. The object expression,
instance()->applicationName(), is encoded as an INDIRECT_REF of a
COMPOUND_EXPR
*(*instance ();, &TARGET_EXPR <D.2383, QCoreApplication::applicationName ()>;);
which lvalue_kind deems an lvalue.
This issue is similar to PR88103 except that here the original compound
object expression is a prvalue rather than an xvalue. The fix there was to
adjust the result of unary_complex_lvalue in build_class_member_access_expr
so that xvalueness of the original expression is preserved. This patch
extends that fix so that rvalueness is preserved more generally.
PR c++/104173
gcc/cp/ChangeLog:
* typeck.cc (build_class_member_access_expr): Extend
unary_complex_lvalue result adjustment to preserve all
rvalues, not just xvalues.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/ref-qual21.C: New test.
Diff:
---
gcc/cp/typeck.cc | 19 ++++++++-----------
gcc/testsuite/g++.dg/cpp0x/ref-qual21.C | 23 +++++++++++++++++++++++
2 files changed, 31 insertions(+), 11 deletions(-)
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 3a28d639cb1..11c9d8aff3e 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -2726,17 +2726,14 @@ 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. */
- {
- tree temp = unary_complex_lvalue (ADDR_EXPR, object);
- if (temp)
- {
- temp = cp_build_fold_indirect_ref (temp);
- if (xvalue_p (object) && !xvalue_p (temp))
- /* Preserve xvalue kind. */
- temp = move (temp);
- object = temp;
- }
- }
+ if (tree temp = unary_complex_lvalue (ADDR_EXPR, object))
+ {
+ temp = cp_build_fold_indirect_ref (temp);
+ if (!lvalue_p (object) && lvalue_p (temp))
+ /* Preserve rvalueness. */
+ temp = move (temp);
+ object = temp;
+ }
/* In [expr.ref], there is an explicit list of the valid choices for
MEMBER. We check for each of those cases here. */
diff --git a/gcc/testsuite/g++.dg/cpp0x/ref-qual21.C b/gcc/testsuite/g++.dg/cpp0x/ref-qual21.C
new file mode 100644
index 00000000000..7f867c21706
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/ref-qual21.C
@@ -0,0 +1,23 @@
+// PR c++/104173
+// { dg-do compile { target c++11 } }
+
+struct QString {
+ QString toLower() &&;
+};
+
+struct QCoreApplication {
+ static QString applicationName();
+};
+
+QCoreApplication* instance();
+
+void f() {
+ instance()->applicationName().toLower();
+}
+
+template<class...>
+void g() {
+ instance()->applicationName().toLower();
+}
+
+template void g<>();
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