Message ID | 20210311085239.GH745611@tucnak |
---|---|
State | New |
Headers | show |
Series | c++: Fix up calls to immediate functions returning reference [PR99507] | expand |
On 3/11/21 3:52 AM, Jakub Jelinek wrote: > Hi! > > build_cxx_call calls convert_from_reference at the end, so if an immediate > function returns a reference, we were constant evaluating not just that > call, but that call wrapped in an INDIRECT_REF. That unfortunately means > it can constant evaluate to something non-addressable, so if code later > needs to take its address it will fail. > > The following patch fixes that by undoing the convert_from_reference > wrapping for the cxx_constant_value evaluation and readdding it ad the end. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? ok. Maybe a comment about '// unwrap the convert from reference'? > > 2021-03-11 Jakub Jelinek <jakub@redhat.com> > > PR c++/99507 > * call.c (build_over_call): For immediate evaluation of functions > that return references, undo convert_from_reference effects before > calling cxx_constant_value and call convert_from_reference > afterwards. > > * g++.dg/cpp2a/consteval19.C: New test. > > --- gcc/cp/call.c.jj 2021-03-06 10:17:01.687304578 +0100 > +++ gcc/cp/call.c 2021-03-10 13:51:29.121445195 +0100 > @@ -9504,6 +9504,8 @@ build_over_call (struct z_candidate *can > if (immediate_invocation_p (fndecl, nargs)) > { > tree obj_arg = NULL_TREE; > + if (REFERENCE_REF_P (call)) > + call = TREE_OPERAND (call, 0); > if (DECL_CONSTRUCTOR_P (fndecl)) > obj_arg = cand->first_arg ? cand->first_arg : (*args)[0]; > if (obj_arg && is_dummy_object (obj_arg)) > @@ -9527,6 +9529,7 @@ build_over_call (struct z_candidate *can > call = cxx_constant_value (call, obj_arg); > if (obj_arg && !error_operand_p (call)) > call = build2 (INIT_EXPR, void_type_node, obj_arg, call); > + call = convert_from_reference (call); > } > } > return call; > --- gcc/testsuite/g++.dg/cpp2a/consteval19.C.jj 2021-03-10 14:20:58.018835190 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/consteval19.C 2021-03-10 14:20:16.642294167 +0100 > @@ -0,0 +1,6 @@ > +// PR c++/99507 > +// { dg-do compile { target c++20 } } > + > +constexpr int i{0}; > +consteval const int &iref () { return i; } > +const int *a{&iref ()}; > > Jakub >
On 3/11/21 3:52 AM, Jakub Jelinek wrote: > Hi! > > build_cxx_call calls convert_from_reference at the end, so if an immediate > function returns a reference, we were constant evaluating not just that > call, but that call wrapped in an INDIRECT_REF. That unfortunately means > it can constant evaluate to something non-addressable, so if code later > needs to take its address it will fail. > > The following patch fixes that by undoing the convert_from_reference > wrapping for the cxx_constant_value evaluation and readdding it ad the end. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? OK. > 2021-03-11 Jakub Jelinek <jakub@redhat.com> > > PR c++/99507 > * call.c (build_over_call): For immediate evaluation of functions > that return references, undo convert_from_reference effects before > calling cxx_constant_value and call convert_from_reference > afterwards. > > * g++.dg/cpp2a/consteval19.C: New test. > > --- gcc/cp/call.c.jj 2021-03-06 10:17:01.687304578 +0100 > +++ gcc/cp/call.c 2021-03-10 13:51:29.121445195 +0100 > @@ -9504,6 +9504,8 @@ build_over_call (struct z_candidate *can > if (immediate_invocation_p (fndecl, nargs)) > { > tree obj_arg = NULL_TREE; > + if (REFERENCE_REF_P (call)) > + call = TREE_OPERAND (call, 0); > if (DECL_CONSTRUCTOR_P (fndecl)) > obj_arg = cand->first_arg ? cand->first_arg : (*args)[0]; > if (obj_arg && is_dummy_object (obj_arg)) > @@ -9527,6 +9529,7 @@ build_over_call (struct z_candidate *can > call = cxx_constant_value (call, obj_arg); > if (obj_arg && !error_operand_p (call)) > call = build2 (INIT_EXPR, void_type_node, obj_arg, call); > + call = convert_from_reference (call); > } > } > return call; > --- gcc/testsuite/g++.dg/cpp2a/consteval19.C.jj 2021-03-10 14:20:58.018835190 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/consteval19.C 2021-03-10 14:20:16.642294167 +0100 > @@ -0,0 +1,6 @@ > +// PR c++/99507 > +// { dg-do compile { target c++20 } } > + > +constexpr int i{0}; > +consteval const int &iref () { return i; } > +const int *a{&iref ()}; > > Jakub >
--- gcc/cp/call.c.jj 2021-03-06 10:17:01.687304578 +0100 +++ gcc/cp/call.c 2021-03-10 13:51:29.121445195 +0100 @@ -9504,6 +9504,8 @@ build_over_call (struct z_candidate *can if (immediate_invocation_p (fndecl, nargs)) { tree obj_arg = NULL_TREE; + if (REFERENCE_REF_P (call)) + call = TREE_OPERAND (call, 0); if (DECL_CONSTRUCTOR_P (fndecl)) obj_arg = cand->first_arg ? cand->first_arg : (*args)[0]; if (obj_arg && is_dummy_object (obj_arg)) @@ -9527,6 +9529,7 @@ build_over_call (struct z_candidate *can call = cxx_constant_value (call, obj_arg); if (obj_arg && !error_operand_p (call)) call = build2 (INIT_EXPR, void_type_node, obj_arg, call); + call = convert_from_reference (call); } } return call; --- gcc/testsuite/g++.dg/cpp2a/consteval19.C.jj 2021-03-10 14:20:58.018835190 +0100 +++ gcc/testsuite/g++.dg/cpp2a/consteval19.C 2021-03-10 14:20:16.642294167 +0100 @@ -0,0 +1,6 @@ +// PR c++/99507 +// { dg-do compile { target c++20 } } + +constexpr int i{0}; +consteval const int &iref () { return i; } +const int *a{&iref ()};