| Message ID | 20191127234443.GF10088@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | [C++] Fix OBJ_TYPE_REF constexpr handling (PR c++/92695) | expand |
On Thu, Nov 28, 2019 at 12:44:43AM +0100, Jakub Jelinek wrote: > Hi! > > On the following testcase the constexpr evaluation of the virtual call > fails, because what cxx_eval_constant_expression returns for > OBJ_TYPE_REF_OBJECT is actually not ADDR_EXPR, but ADDR_EXPR wrapped in > a NOP_EXPR. > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for > trunk? Looks ok. In fact, when working on constexpr dynamic_cast, I ran into a very similar problem and also added STRIP_NOPS. -- Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
On 11/27/19 6:44 PM, Jakub Jelinek wrote: > Hi! > > On the following testcase the constexpr evaluation of the virtual call > fails, because what cxx_eval_constant_expression returns for > OBJ_TYPE_REF_OBJECT is actually not ADDR_EXPR, but ADDR_EXPR wrapped in > a NOP_EXPR. > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for > trunk? OK. > 2019-11-27 Jakub Jelinek <jakub@redhat.com> > > PR c++/92695 > * constexpr.c (cxx_eval_constant_expression) <case OBJ_TYPE_REF>: Use > STRIP_NOPS before checking for ADDR_EXPR. > > * g++.dg/cpp2a/constexpr-virtual15.C: New test. > > --- gcc/cp/constexpr.c.jj 2019-11-27 17:53:37.477566346 +0100 > +++ gcc/cp/constexpr.c 2019-11-27 21:16:51.094188509 +0100 > @@ -5566,6 +5566,7 @@ cxx_eval_constant_expression (const cons > tree obj = OBJ_TYPE_REF_OBJECT (t); > obj = cxx_eval_constant_expression (ctx, obj, lval, non_constant_p, > overflow_p); > + STRIP_NOPS (obj); > /* We expect something in the form of &x.D.2103.D.2094; get x. */ > if (TREE_CODE (obj) != ADDR_EXPR > || !DECL_P (get_base_address (TREE_OPERAND (obj, 0)))) > --- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C.jj 2019-11-27 21:18:15.418895652 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C 2019-11-27 21:17:48.602306802 +0100 > @@ -0,0 +1,7 @@ > +// PR c++/92695 > +// { dg-do compile { target c++2a } } > + > +struct A { virtual int get() = 0; }; > +struct B : A { constexpr int get() override { return 10; } }; > +struct D { B b[2]; A* c{&(b[0])}; }; > +static_assert(D{}.c->get() == 10); > > Jakub >
--- gcc/cp/constexpr.c.jj 2019-11-27 17:53:37.477566346 +0100 +++ gcc/cp/constexpr.c 2019-11-27 21:16:51.094188509 +0100 @@ -5566,6 +5566,7 @@ cxx_eval_constant_expression (const cons tree obj = OBJ_TYPE_REF_OBJECT (t); obj = cxx_eval_constant_expression (ctx, obj, lval, non_constant_p, overflow_p); + STRIP_NOPS (obj); /* We expect something in the form of &x.D.2103.D.2094; get x. */ if (TREE_CODE (obj) != ADDR_EXPR || !DECL_P (get_base_address (TREE_OPERAND (obj, 0)))) --- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C.jj 2019-11-27 21:18:15.418895652 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual15.C 2019-11-27 21:17:48.602306802 +0100 @@ -0,0 +1,7 @@ +// PR c++/92695 +// { dg-do compile { target c++2a } } + +struct A { virtual int get() = 0; }; +struct B : A { constexpr int get() override { return 10; } }; +struct D { B b[2]; A* c{&(b[0])}; }; +static_assert(D{}.c->get() == 10);