From: David Malcolm <dmalcolm@redhat.com>
To: Jason Merrill <jason@redhat.com>
Cc: Nathan Sidwell <nathan@acm.org>, Jakub Jelinek <jakub@redhat.com>,
Richard Biener <richard.guenther@gmail.com>,
gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] RFC: Preserving locations for variable-uses and constants (PR 43486)
Date: Tue, 31 Oct 2017 21:28:00 -0000 [thread overview]
Message-ID: <1509484153.15469.45.camel@redhat.com> (raw)
In-Reply-To: <CADzB+2nobdRKunr_Crw2aKKM8aJyTGFb6YGUR2SqgVhYfT_r3g@mail.gmail.com>
On Tue, 2017-10-24 at 09:53 -0400, Jason Merrill wrote:
> On Fri, Oct 20, 2017 at 5:53 PM, David Malcolm <dmalcolm@redhat.com>
> wrote:
> > Design questions:
> >
> > * The patch introduces a new kind of tree node, currently called
> > DECL_WRAPPER_EXPR (although it's used for wrapping constants as
> > well
> > as decls). Should wrappers be a new kind of tree node, or should
> > they
> > reuse an existing TREE_CODE? (e.g. NOP_EXPR, CONVERT_EXPR, etc).
> > * NOP_EXPR: seems to be for use as an rvalue
> > * CONVERT_EXPR: for type conversions
> > * NON_LVALUE_EXPR: "Value is same as argument, but guaranteed
> > not an
> > lvalue"
> > * but we *do* want to support lvalues here
>
> I think using NON_LVALUE_EXPR for constants would be appropriate.
>
> > * VIEW_CONVERT_EXPR: viewing one thing as of a different type
> > * can it support lvalues?
>
> Yes, the purpose of VIEW_CONVERT_EXPR is to support lvalues, it seems
> like the right choice.
>
> Jason
Thanks. I've been working on a new version of the patch using those
tree codes, but have run into an issue.
In g++.dg/conversion/reinterpret1.C:
// PR c++/15076
struct Y { Y(int &); };
int v;
Y y1(reinterpret_cast<int>(v)); // { dg-error "" }
With trunk, this successfully generates an error:
reinterpret1.C:6:6: error: cannot bind non-const lvalue reference of type âint&â to an rvalue of type âintâ
Y y1(reinterpret_cast<int>(v)); // { dg-error "" }
^~~~~~~~~~~~~~~~~~~~~~~~
reinterpret1.C:3:12: note: initializing argument 1 of âY::Y(int&)â
struct Y { Y(int &); };
^
where internally there's a NON_LVALUE_EXPR around a VAR_DECL, where
both have the same type:
(gdb) call debug_tree (expr)
<non_lvalue_expr 0x7ffff145f6e0
type <integer_type 0x7ffff132e5e8 int public type_6 SI
size <integer_cst 0x7ffff1331120 constant 32>
unit-size <integer_cst 0x7ffff1331138 constant 4>
align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type 0x7ffff132e5e8 precision:32 min <integer_cst 0x7ffff13310d8 -2147483648> max <integer_cst 0x7ffff13310f0 2147483647>
pointer_to_this <pointer_type 0x7ffff1336a80> reference_to_this <reference_type 0x7ffff144ca80>>
arg:0 <var_decl 0x7ffff7ffbd80 v type <integer_type 0x7ffff132e5e8 int>
used public static tree_1 read SI /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C:5:5 size <integer_cst 0x7ffff1331120 32> unit-size <integer_cst 0x7ffff1331138 4>
align:32 warn_if_not_align:0 context <translation_unit_decl 0x7ffff131e168 /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C>
chain <type_decl 0x7ffff141a720 Y type <record_type 0x7ffff144c150 Y>
public decl_2 VOID /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C:3:8
align:8 warn_if_not_align:0 context <translation_unit_decl 0x7ffff131e168 /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C> chain <function_decl 0x7ffff144f800 __cxa_call_unexpected>>>
/home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C:6:6 start: /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C:6:6 finish: /home/david/coding-3/gcc-git-expr-vs-decl/src/gcc/testsuite/g++.dg/conversion/reinterpret1.C:6:29>
The problem is that this reinterpret cast "looks" just like one of my
location wrappers.
I see a similar issue with constants, where with:
struct Y { Y(int &); };
Y y1(reinterpret_cast<int>(42));
trunk generates an error like the above, but my code handles the
NON_LVALUE_EXPR<int>(INTEGER_CST<int>(42))
as if it were a location wrapper around the INTEGER_CST, and thus
doesn't emit the error.
I can envisage a few hackish solutions, like assuming that there will
be a location wrapper around such a constant, and thus to expect:
NON_LVALUE_EXPR<int>(NON_LVALUE_EXPR<int>(INTEGER_CST<int>(42)))
but this seems clunky and fragile; maybe we do need a new tree code for
this (e.g. LOCATION_WRAPPER or somesuch?)
Thoughts?
Thanks
Dave
next prev parent reply other threads:[~2017-10-31 21:09 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-20 22:38 David Malcolm
2017-10-24 14:05 ` Jason Merrill
2017-10-31 21:28 ` David Malcolm [this message]
2017-11-02 14:46 ` Jason Merrill
2017-11-10 21:43 ` [PATCH v2: 00/14] " David Malcolm
2017-11-10 21:43 ` [PATCH 06/14] Fix Wsizeof-pointer-memaccess*.c David Malcolm
2017-12-11 23:37 ` Jason Merrill
2017-12-18 2:04 ` [v2 of PATCH 06/14] Strip location wrappers in operand_equal_p David Malcolm
2017-12-18 8:00 ` Jakub Jelinek
2017-12-19 20:13 ` Jason Merrill
2017-12-19 20:49 ` Jakub Jelinek
2017-12-19 21:59 ` Jason Merrill
2017-12-19 22:03 ` Jakub Jelinek
2017-12-20 0:41 ` [PATCH] Eliminate location wrappers in tree_nop_conversion/STRIP_NOPS David Malcolm
2017-12-20 4:27 ` Jeff Law
2017-11-10 21:43 ` [PATCH 07/14] reject_gcc_builtin: strip any location wrappers David Malcolm
2017-12-11 23:38 ` Jason Merrill
2017-11-10 21:43 ` [PATCH 02/14] Support for adding and stripping location_t wrapper nodes David Malcolm
2017-11-15 6:31 ` Trevor Saunders
2017-11-15 11:23 ` Richard Biener
2017-11-15 15:40 ` David Malcolm
2017-11-16 10:04 ` Richard Biener
2017-11-30 17:25 ` [PATCH v2.1] " David Malcolm
2017-11-30 17:46 ` Jason Merrill
2017-11-30 18:38 ` [PATCH, v2.2] " David Malcolm
2017-11-30 20:30 ` Jason Merrill
2017-11-10 21:43 ` [PATCH 03/14] C++: add location_t wrapper nodes during parsing (minimal impl) David Malcolm
2017-12-12 2:10 ` Jason Merrill
2017-12-14 19:25 ` David Malcolm
2017-12-15 15:02 ` Jason Merrill
2017-12-15 16:35 ` David Malcolm
2017-12-15 18:59 ` Jason Merrill
2017-12-15 22:49 ` David Malcolm
2017-12-29 17:03 ` [v2 of PATCH " David Malcolm
2018-01-05 20:29 ` Jason Merrill
2018-01-05 22:20 ` David Malcolm
2018-01-08 17:10 ` Location wrappers vs decls that change type (was Re: [v2 of PATCH 03/14] C++: add location_t wrapper nodes during parsing (minimal impl)) David Malcolm
2018-01-08 17:14 ` Nathan Sidwell
2018-01-08 17:18 ` Jakub Jelinek
2018-01-08 17:28 ` Nathan Sidwell
2018-01-08 18:08 ` David Malcolm
2018-01-08 18:23 ` Jakub Jelinek
2018-01-09 11:34 ` [PATCH v2.4 of 02/14] Support for adding and stripping location_t wrapper nodes David Malcolm
2018-01-09 14:59 ` Jason Merrill
2018-01-08 21:48 ` [v2 of PATCH 03/14] C++: add location_t wrapper nodes during parsing (minimal impl) Jason Merrill
2018-01-08 21:03 ` David Malcolm
2018-01-08 21:59 ` Jason Merrill
2018-01-08 22:27 ` Jason Merrill
2018-01-09 12:03 ` [PATCH v3 of " David Malcolm
2018-01-09 14:39 ` Jason Merrill
2018-01-09 14:39 ` Jakub Jelinek
2018-01-09 18:32 ` [PATCH v4 " David Malcolm
2018-01-09 19:45 ` Jason Merrill
2017-11-10 21:43 ` [PATCH 05/14] tree.c: strip location wrappers from integer_zerop etc David Malcolm
2017-12-11 23:36 ` Jason Merrill
2017-12-16 13:09 ` [PATCH] C++: handle locations wrappers when calling warn_for_memset David Malcolm
2017-12-16 20:01 ` Martin Sebor
2017-12-19 20:02 ` Jason Merrill
2017-12-20 19:23 ` [v3 of 05/14] " David Malcolm
2017-12-21 4:58 ` Jason Merrill
2017-11-10 21:43 ` [PATCH 01/14] C++: preserve locations within build_address David Malcolm
2017-12-11 23:25 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 08/14] cp/tree.c: strip location wrappers in lvalue_kind David Malcolm
2017-12-11 23:39 ` Jason Merrill
2017-12-20 22:11 ` [v2 of PATCH " David Malcolm
2017-12-21 4:56 ` Jason Merrill
2017-12-21 17:47 ` [v3 " David Malcolm
2017-12-21 22:44 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 13/14] c-format.c: handle location wrappers David Malcolm
2017-12-11 23:45 ` Jason Merrill
2017-12-17 16:26 ` [v2 of PATCH " David Malcolm
2017-12-19 19:55 ` Jason Merrill
2017-12-20 17:33 ` David Malcolm
2017-12-21 5:03 ` Jason Merrill
2017-12-22 19:07 ` [v3 " David Malcolm
2018-01-05 17:35 ` PING " David Malcolm
2018-01-05 17:48 ` Joseph Myers
2018-01-05 20:21 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 09/14] Strip location wrappers in null_ptr_cst_p David Malcolm
2017-12-11 23:39 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 14/14] pp_c_cast_expression: don't print casts for location wrappers David Malcolm
2017-12-11 23:46 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 10/14] warn_for_memset: handle " David Malcolm
2017-12-11 23:41 ` Jason Merrill
2017-11-10 21:44 ` [PATCH 04/14] Update testsuite to show improvements David Malcolm
2017-11-10 21:44 ` [PATCH 11/14] Handle location wrappers in string_conv_p David Malcolm
2017-12-11 23:42 ` Jason Merrill
2017-11-10 22:11 ` [PATCH 12/14] C++: introduce null_node_p David Malcolm
2017-12-11 23:42 ` Jason Merrill
2017-11-13 19:20 ` [PATCH v2: 00/14] Preserving locations for variable-uses and constants (PR 43486) David Malcolm
2017-11-18 2:50 ` [RFC v3 00/11] C++: locations for (almost) everything " David Malcolm
2017-11-18 2:50 ` [PATCH 03/11] Implement STRIP_ANY_LOCATION_WRAPPER_SAFE David Malcolm
2017-11-18 2:50 ` [PATCH 02/11] cp_tree::maybe_add_location_wrapper: no-op for template decls David Malcolm
2017-11-18 2:50 ` [PATCH 01/11] C++: Add location wrappers for all constants and decls David Malcolm
2017-11-18 2:50 ` [PATCH 06/11] gcc: Handle location wrappers in operand_equal_p David Malcolm
2017-11-18 2:51 ` [PATCH 09/11] objc: handle location wrappers in objc_maybe_build_component_ref David Malcolm
2017-11-18 2:51 ` [PATCH 07/11] c-family: handle location wrappers David Malcolm
2017-11-18 2:51 ` [PATCH 04/11] C++: add cp_expr::strip_any_location_wrapper method David Malcolm
2017-11-18 2:51 ` [PATCH 05/11] C++: finish_call_expr: strip location wrapper David Malcolm
2017-11-18 2:51 ` [PATCH 08/11] C++: handle location wrappers David Malcolm
2017-11-18 3:23 ` [PATCH 11/11] config: handle location wrappers in various attributes (untested) David Malcolm
2017-11-18 3:54 ` [PATCH 10/11] i386: handle location wrappers in ix86_handle_cconv_attribute David Malcolm
2017-11-30 20:54 ` [PATCH v2: 00/14] Preserving locations for variable-uses and constants (PR 43486) David Malcolm
2017-12-11 16:08 ` [PING ^ 2] " David Malcolm
2017-12-17 1:10 ` [PATCH 15/14] Use fold_for_warn in get_atomic_generic_size David Malcolm
2017-12-19 20:35 ` Jason Merrill
2017-12-20 0:50 ` [v2 of PATCH " David Malcolm
2017-12-20 4:22 ` Jason Merrill
2017-12-20 19:33 ` [v3 " David Malcolm
2017-12-21 4:57 ` Jason Merrill
2018-01-10 19:51 ` [committed] Preserving locations for variable-uses and constants (PR c++/43486) David Malcolm
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1509484153.15469.45.camel@redhat.com \
--to=dmalcolm@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jakub@redhat.com \
--cc=jason@redhat.com \
--cc=nathan@acm.org \
--cc=richard.guenther@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).