| Message ID | 20210210150531.GL4020736@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | c++, v2: Consider addresses of heap artificial vars always non-NULL [PR98988, PR99031] | expand |
On 2/10/21 10:05 AM, Jakub Jelinek wrote: > On Tue, Feb 09, 2021 at 04:08:03PM -0500, Jason Merrill via Gcc-patches wrote: >>> They are not in the symtab from the C++ FE. And we don't allow those VAR_DECLs or their >>> addresses to leak into the IL anyway. >>> But, they are TREE_STATIC because pretending they are automatic didn't >>> really work (e.g. address of automatic variables is not a constant expression). >>> The generic folding code uses maybe_nonzero_address predicate which >>> apprently creates a symtab entry for them but as nothing uses them they >>> won't be emitted. >> >> Ah. >> >>> If we wanted to avoid that, we'd need to either add some generic VAR_DECL >>> bit for those vars or add a target hook that would return true for them and >>> then handle them in the middle-end. >> >> I'm surprised that nonzero_address has such a limited set of things it will >> actually believe have non-zero addresses with >> -fno-delete-null-pointer-checks. But it seems that we should be able to >> arrange to satisfy >> >>> if (definition && !DECL_EXTERNAL (decl) >> >> since these "variables" are indeed defined within the current translation >> unit. > > Doing that seems to work and as added benefit it fixes another PR that has > been filed recently. I need to create the varpool node explicitly and call > a method that sets the definition member in there, but I can also unregister > those varpool nodes at the end of constexpr processing, as the processing > ensured they don't leak outside of the processing. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > 2021-02-10 Jakub Jelinek <jakub@redhat.com> > > PR c++/98988 > PR c++/99031 > * constexpr.c: Include cgraph.h. > (cxx_eval_call_expression): Call varpool_node::finalize_decl on > heap artificial vars. > (cxx_eval_outermost_constant_expr): Remove varpool nodes for > heap artificial vars. > > * g++.dg/cpp2a/constexpr-new16.C: New test. > * g++.dg/cpp2a/constexpr-new17.C: New test. > > --- gcc/cp/constexpr.c.jj 2021-02-09 10:05:28.820833601 +0100 > +++ gcc/cp/constexpr.c 2021-02-10 11:31:16.567984809 +0100 > @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3. > #include "timevar.h" > #include "fold-const-call.h" > #include "stor-layout.h" > +#include "cgraph.h" > > static bool verify_constant (tree, bool, bool *, bool *); > #define VERIFY_CONSTANT(X) \ > @@ -2340,6 +2341,7 @@ cxx_eval_call_expression (const constexp > type); > DECL_ARTIFICIAL (var) = 1; > TREE_STATIC (var) = 1; > + varpool_node::finalize_decl (var); Please add a comment that this is for nonzero_address. OK with that change. > ctx->global->heap_vars.safe_push (var); > ctx->global->values.put (var, NULL_TREE); > return fold_convert (ptr_type_node, build_address (var)); > @@ -7199,15 +7201,18 @@ cxx_eval_outermost_constant_expr (tree t > non_constant_p = true; > } > FOR_EACH_VEC_ELT (global_ctx.heap_vars, i, heap_var) > - if (DECL_NAME (heap_var) != heap_deleted_identifier) > - { > - if (!allow_non_constant && !non_constant_p) > - error_at (DECL_SOURCE_LOCATION (heap_var), > - "%qE is not a constant expression because allocated " > - "storage has not been deallocated", t); > - r = t; > - non_constant_p = true; > - } > + { > + if (DECL_NAME (heap_var) != heap_deleted_identifier) > + { > + if (!allow_non_constant && !non_constant_p) > + error_at (DECL_SOURCE_LOCATION (heap_var), > + "%qE is not a constant expression because allocated " > + "storage has not been deallocated", t); > + r = t; > + non_constant_p = true; > + } > + varpool_node::get (heap_var)->remove (); > + } > } > > /* Check that immediate invocation does not return an expression referencing > --- gcc/testsuite/g++.dg/cpp2a/constexpr-new16.C.jj 2021-02-10 11:11:00.117658382 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new16.C 2021-02-10 11:11:00.117658382 +0100 > @@ -0,0 +1,13 @@ > +// PR c++/98988 > +// { dg-do compile { target c++20 } } > +// { dg-options "-fno-delete-null-pointer-checks" } > + > +constexpr bool > +foo () > +{ > + auto ptr = new int(); > + delete ptr; > + return true; > +} > + > +static_assert (foo ()); > --- gcc/testsuite/g++.dg/cpp2a/constexpr-new17.C.jj 2021-02-10 13:04:17.947606440 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new17.C 2021-02-10 13:04:06.417738050 +0100 > @@ -0,0 +1,15 @@ > +// PR c++/99031 > +// { dg-do compile { target c++20 } } > + > +constexpr bool > +foo () > +{ > + auto a = new int; > + auto b = new int; > + bool r = a == b; > + delete b; > + delete a; > + return r; > +} > + > +static_assert (!foo ()); > > > Jakub >
--- gcc/cp/constexpr.c.jj 2021-02-09 10:05:28.820833601 +0100 +++ gcc/cp/constexpr.c 2021-02-10 11:31:16.567984809 +0100 @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3. #include "timevar.h" #include "fold-const-call.h" #include "stor-layout.h" +#include "cgraph.h" static bool verify_constant (tree, bool, bool *, bool *); #define VERIFY_CONSTANT(X) \ @@ -2340,6 +2341,7 @@ cxx_eval_call_expression (const constexp type); DECL_ARTIFICIAL (var) = 1; TREE_STATIC (var) = 1; + varpool_node::finalize_decl (var); ctx->global->heap_vars.safe_push (var); ctx->global->values.put (var, NULL_TREE); return fold_convert (ptr_type_node, build_address (var)); @@ -7199,15 +7201,18 @@ cxx_eval_outermost_constant_expr (tree t non_constant_p = true; } FOR_EACH_VEC_ELT (global_ctx.heap_vars, i, heap_var) - if (DECL_NAME (heap_var) != heap_deleted_identifier) - { - if (!allow_non_constant && !non_constant_p) - error_at (DECL_SOURCE_LOCATION (heap_var), - "%qE is not a constant expression because allocated " - "storage has not been deallocated", t); - r = t; - non_constant_p = true; - } + { + if (DECL_NAME (heap_var) != heap_deleted_identifier) + { + if (!allow_non_constant && !non_constant_p) + error_at (DECL_SOURCE_LOCATION (heap_var), + "%qE is not a constant expression because allocated " + "storage has not been deallocated", t); + r = t; + non_constant_p = true; + } + varpool_node::get (heap_var)->remove (); + } } /* Check that immediate invocation does not return an expression referencing --- gcc/testsuite/g++.dg/cpp2a/constexpr-new16.C.jj 2021-02-10 11:11:00.117658382 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new16.C 2021-02-10 11:11:00.117658382 +0100 @@ -0,0 +1,13 @@ +// PR c++/98988 +// { dg-do compile { target c++20 } } +// { dg-options "-fno-delete-null-pointer-checks" } + +constexpr bool +foo () +{ + auto ptr = new int(); + delete ptr; + return true; +} + +static_assert (foo ()); --- gcc/testsuite/g++.dg/cpp2a/constexpr-new17.C.jj 2021-02-10 13:04:17.947606440 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new17.C 2021-02-10 13:04:06.417738050 +0100 @@ -0,0 +1,15 @@ +// PR c++/99031 +// { dg-do compile { target c++20 } } + +constexpr bool +foo () +{ + auto a = new int; + auto b = new int; + bool r = a == b; + delete b; + delete a; + return r; +} + +static_assert (!foo ());