| Message ID | 20230713184923.3699777-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: copy elision of object arg in static memfn call [PR110441] | expand |
On 7/13/23 14:49, Patrick Palka wrote: > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for > trunk? OK. > -- >8 -- > > Here the call A().f() is represented as a COMPOUND_EXPR whose first > operand is the otherwise unused object argument A() and second operand > is the call result (both are TARGET_EXPRs). Within the return statement, > this outermost COMPOUND_EXPR ends up foiling the copy elision check in > build_special_member_call, resulting in us introducing a bogus call to the > deleted move constructor. (Within the variable initialization, which goes > through ocp_convert instead of convert_for_initialization, we've already > been eliding the copy despite the outermost COMPOUND_EXPR ever since > r10-7410-g72809d6fe8e085 made ocp_convert look through COMPOUND_EXPR). > > In contrast, I noticed '(A(), A::f())' (which should be equivalent to > the above call) is represented with the COMPOUND_EXPR inside the RHS's > TARGET_EXPR initializer thanks to a special case in cp_build_compound_expr > thus avoiding the issue. > > So this patch fixes this by making keep_unused_object_arg > use cp_build_compound_expr as well. > > PR c++/110441 > > gcc/cp/ChangeLog: > > * call.cc (keep_unused_object_arg): Use cp_build_compound_expr > instead of building a COMPOUND_EXPR directly. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp1z/elide8.C: New test. > --- > gcc/cp/call.cc | 2 +- > gcc/testsuite/g++.dg/cpp1z/elide8.C | 25 +++++++++++++++++++++++++ > 2 files changed, 26 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp1z/elide8.C > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > index 119063979fa..b0a69cb46d4 100644 > --- a/gcc/cp/call.cc > +++ b/gcc/cp/call.cc > @@ -5218,7 +5218,7 @@ keep_unused_object_arg (tree result, tree obj, tree fn) > if (TREE_THIS_VOLATILE (a)) > a = build_this (a); > if (TREE_SIDE_EFFECTS (a)) > - return build2 (COMPOUND_EXPR, TREE_TYPE (result), a, result); > + return cp_build_compound_expr (a, result, tf_warning_or_error); > return result; > } > > diff --git a/gcc/testsuite/g++.dg/cpp1z/elide8.C b/gcc/testsuite/g++.dg/cpp1z/elide8.C > new file mode 100644 > index 00000000000..7d471be8a2a > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp1z/elide8.C > @@ -0,0 +1,25 @@ > +// PR c++/110441 > +// { dg-do compile { target c++11 } } > + > +struct immovable { > + immovable(immovable &&) = delete; > +}; > + > +struct A { > + static immovable f(); > +}; > + > +immovable f() { > + immovable m = A().f(); // { dg-error "deleted" "" { target c++14_down } } > + return A().f(); // { dg-error "deleted" "" { target c++14_down } } > +} > + > +struct B { > + A* operator->(); > +}; > + > +immovable g() { > + B b; > + immovable m = b->f(); // { dg-error "deleted" "" { target c++14_down } } > + return b->f(); // { dg-error "deleted" "" { target c++14_down } } > +}
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc index 119063979fa..b0a69cb46d4 100644 --- a/gcc/cp/call.cc +++ b/gcc/cp/call.cc @@ -5218,7 +5218,7 @@ keep_unused_object_arg (tree result, tree obj, tree fn) if (TREE_THIS_VOLATILE (a)) a = build_this (a); if (TREE_SIDE_EFFECTS (a)) - return build2 (COMPOUND_EXPR, TREE_TYPE (result), a, result); + return cp_build_compound_expr (a, result, tf_warning_or_error); return result; } diff --git a/gcc/testsuite/g++.dg/cpp1z/elide8.C b/gcc/testsuite/g++.dg/cpp1z/elide8.C new file mode 100644 index 00000000000..7d471be8a2a --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/elide8.C @@ -0,0 +1,25 @@ +// PR c++/110441 +// { dg-do compile { target c++11 } } + +struct immovable { + immovable(immovable &&) = delete; +}; + +struct A { + static immovable f(); +}; + +immovable f() { + immovable m = A().f(); // { dg-error "deleted" "" { target c++14_down } } + return A().f(); // { dg-error "deleted" "" { target c++14_down } } +} + +struct B { + A* operator->(); +}; + +immovable g() { + B b; + immovable m = b->f(); // { dg-error "deleted" "" { target c++14_down } } + return b->f(); // { dg-error "deleted" "" { target c++14_down } } +}