From: Jason Merrill <jason@redhat.com>
To: Marek Polacek <polacek@redhat.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
Joseph Myers <joseph@codesourcery.com>,
Richard Biener <rguenther@suse.de>
Subject: Re: [PATCH v2] c-family: Honor -Wno-init-self for cv-qual vars [PR102633]
Date: Wed, 10 Aug 2022 18:05:40 -0800 [thread overview]
Message-ID: <c7d80080-02ca-2880-1826-db83ecdc1964@redhat.com> (raw)
In-Reply-To: <YvFev6S768sJdPpO@redhat.com>
On 8/8/22 12:06, Marek Polacek wrote:
> On Sat, Aug 06, 2022 at 03:29:05PM -0700, Jason Merrill wrote:
>> On 7/26/22 14:31, Marek Polacek wrote:
>>> On Tue, Jul 26, 2022 at 04:24:18PM -0400, Jason Merrill wrote:
>>>> On 7/26/22 15:03, Marek Polacek wrote:
>>>>> Since r11-5188-g32934a4f45a721, we drop qualifiers during l-to-r
>>>>> conversion by creating a NOP_EXPR. For e.g.
>>>>>
>>>>> const int i = i;
>>>>>
>>>>> that means that the DECL_INITIAL is '(int) i' and not 'i' anymore.
>>>>> Consequently, we don't suppress_warning here:
>>>>>
>>>>> 711 case DECL_EXPR:
>>>>> 715 if (VAR_P (DECL_EXPR_DECL (*expr_p))
>>>>> 716 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
>>>>> 717 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
>>>>> 718 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
>>>>> 719 && !warn_init_self)
>>>>> 720 suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self);
>>>>>
>>>>> because of the check on line 718 -- (int) i is not i. So -Wno-init-self
>>>>> doesn't disable the warning as it's supposed to.
>>>>>
>>>>> The following patch fixes it...except it doesn't, for volatile variables
>>>>> in C++. The problem is that for
>>>>>
>>>>> volatile int k = k;
>>>>>
>>>>> we see that the initializer has TREE_SIDE_EFFECTS, so we perform dynamic
>>>>> initialization. So there's no DECL_INITIAL and the suppress_warning
>>>>> call above is never done. I suppose we could amend get_no_uninit_warning
>>>>> to return true for volatile-qualified expressions. I mean, can we ever
>>>>> say for a fact that a volatile variable is uninitialized?
>>>>>
>>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>>>
>>>>> PR middle-end/102633
>>>>>
>>>>> gcc/c-family/ChangeLog:
>>>>>
>>>>> * c-gimplify.cc (c_gimplify_expr): Strip NOPs of DECL_INITIAL.
>>>>
>>>> I wonder if we want to handle this i = i case earlier, like in finish_decl.
>>>
>>> I could, something like
>>>
>>> @@ -5381,7 +5381,14 @@ finish_decl (tree decl, location_t init_loc, tree init,
>>> init = NULL_TREE;
>>>
>>> if (init)
>>> - store_init_value (init_loc, decl, init, origtype);
>>> + {
>>> + /* In the self-init case, undo the artificial NOP_EXPR we may have
>>> + added in convert_lvalue_to_rvalue so that c_gimplify_expr/DECL_EXPR
>>> + can perform suppress_warning. */
>>> + if (TREE_CODE (init) == NOP_EXPR && TREE_OPERAND (init, 0) == decl)
>>> + init = TREE_OPERAND (init, 0);
>>> + store_init_value (init_loc, decl, init, origtype);
>>> + }
>>>
>>> but then I'd have to do the same thing in cp_finish_decl because
>>> decay_conversion also adds a NOP_EXPR for cv-qualified non-class prvalues.
>>> Is that what we want? To me that seems less clean than having c_gimplify_expr
>>> see through NOP_EXPRs.
>>
>> I was thinking of checking the form of the initializer before
>> decay_conversion or anything else messes with it, and calling
>> suppress_warning at that point instead of in c_gimplify_expr.
>
> Aaah, okay. Here's a patch that does it. In the C FE it has to
> happen really early. Now both front ends behave the same wrt volatiles!
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
LGTM.
> -- >8 --
> Since r11-5188-g32934a4f45a721, we drop qualifiers during l-to-r
> conversion by creating a NOP_EXPR. For e.g.
>
> const int i = i;
>
> that means that the DECL_INITIAL is '(int) i' and not 'i' anymore.
> Consequently, we don't suppress_warning here:
>
> 711 case DECL_EXPR:
> 715 if (VAR_P (DECL_EXPR_DECL (*expr_p))
> 716 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
> 717 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
> 718 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
> 719 && !warn_init_self)
> 720 suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self);
>
> because of the check on line 718 -- (int) i is not i. So -Wno-init-self
> doesn't disable the warning as it's supposed to.
>
> The following patch fixes it by moving the suppress_warning call from
> c_gimplify_expr to the front ends, at points where we haven't created
> the NOP_EXPR yet.
>
> PR middle-end/102633
>
> gcc/c-family/ChangeLog:
>
> * c-gimplify.cc (c_gimplify_expr) <case DECL_EXPR>: Don't call
> suppress_warning here.
>
> gcc/c/ChangeLog:
>
> * c-parser.cc (c_parser_initializer): Add new tree parameter. Use it.
> Call suppress_warning.
> (c_parser_declaration_or_fndef): Pass d down to c_parser_initializer.
> (c_parser_omp_declare_reduction): Pass omp_priv down to
> c_parser_initializer.
>
> gcc/cp/ChangeLog:
>
> * decl.cc (cp_finish_decl): Call suppress_warning.
>
> gcc/testsuite/ChangeLog:
>
> * c-c++-common/Winit-self1.c: New test.
> * c-c++-common/Winit-self2.c: New test.
> ---
> gcc/c-family/c-gimplify.cc | 12 ---------
> gcc/c/c-parser.cc | 19 ++++++++++++---
> gcc/cp/decl.cc | 8 ++++++
> gcc/testsuite/c-c++-common/Winit-self1.c | 31 ++++++++++++++++++++++++
> gcc/testsuite/c-c++-common/Winit-self2.c | 31 ++++++++++++++++++++++++
> 5 files changed, 85 insertions(+), 16 deletions(-)
> create mode 100644 gcc/testsuite/c-c++-common/Winit-self1.c
> create mode 100644 gcc/testsuite/c-c++-common/Winit-self2.c
>
> diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc
> index a6f26c9b0d3..039a4b93230 100644
> --- a/gcc/c-family/c-gimplify.cc
> +++ b/gcc/c-family/c-gimplify.cc
> @@ -708,18 +708,6 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
> break;
> }
>
> - case DECL_EXPR:
> - /* This is handled mostly by gimplify.cc, but we have to deal with
> - not warning about int x = x; as it is a GCC extension to turn off
> - this warning but only if warn_init_self is zero. */
> - if (VAR_P (DECL_EXPR_DECL (*expr_p))
> - && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
> - && !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
> - && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p))
> - && !warn_init_self)
> - suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self);
> - break;
> -
> case PREINCREMENT_EXPR:
> case PREDECREMENT_EXPR:
> case POSTINCREMENT_EXPR:
> diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
> index 92049d1a101..6ed17ed9c48 100644
> --- a/gcc/c/c-parser.cc
> +++ b/gcc/c/c-parser.cc
> @@ -1521,7 +1521,7 @@ static struct c_arg_info *c_parser_parms_list_declarator (c_parser *, tree,
> static struct c_parm *c_parser_parameter_declaration (c_parser *, tree, bool);
> static tree c_parser_simple_asm_expr (c_parser *);
> static tree c_parser_gnu_attributes (c_parser *);
> -static struct c_expr c_parser_initializer (c_parser *);
> +static struct c_expr c_parser_initializer (c_parser *, tree);
> static struct c_expr c_parser_braced_init (c_parser *, tree, bool,
> struct obstack *);
> static void c_parser_initelt (c_parser *, struct obstack *);
> @@ -2286,7 +2286,7 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
> int flag_sanitize_save = flag_sanitize;
> if (TREE_CODE (d) == PARM_DECL)
> flag_sanitize = 0;
> - init = c_parser_initializer (parser);
> + init = c_parser_initializer (parser, d);
> flag_sanitize = flag_sanitize_save;
> finish_init ();
> }
> @@ -5211,11 +5211,13 @@ c_parser_type_name (c_parser *parser, bool alignas_ok)
> Any expression without commas is accepted in the syntax for the
> constant-expressions, with non-constant expressions rejected later.
>
> + DECL is the declaration we're parsing this initializer for.
> +
> This function is only used for top-level initializers; for nested
> ones, see c_parser_initval. */
>
> static struct c_expr
> -c_parser_initializer (c_parser *parser)
> +c_parser_initializer (c_parser *parser, tree decl)
> {
> if (c_parser_next_token_is (parser, CPP_OPEN_BRACE))
> return c_parser_braced_init (parser, NULL_TREE, false, NULL);
> @@ -5224,6 +5226,15 @@ c_parser_initializer (c_parser *parser)
> struct c_expr ret;
> location_t loc = c_parser_peek_token (parser)->location;
> ret = c_parser_expr_no_commas (parser, NULL);
> + /* This is handled mostly by gimplify.cc, but we have to deal with
> + not warning about int x = x; as it is a GCC extension to turn off
> + this warning but only if warn_init_self is zero. */
> + if (VAR_P (decl)
> + && !DECL_EXTERNAL (decl)
> + && !TREE_STATIC (decl)
> + && ret.value == decl
> + && !warn_init_self)
> + suppress_warning (decl, OPT_Winit_self);
> if (TREE_CODE (ret.value) != STRING_CST
> && TREE_CODE (ret.value) != COMPOUND_LITERAL_EXPR)
> ret = convert_lvalue_to_rvalue (loc, ret, true, true);
> @@ -22576,7 +22587,7 @@ c_parser_omp_declare_reduction (c_parser *parser, enum pragma_context context)
> location_t loc = c_parser_peek_token (parser)->location;
> rich_location richloc (line_table, loc);
> start_init (omp_priv, NULL_TREE, 0, &richloc);
> - struct c_expr init = c_parser_initializer (parser);
> + struct c_expr init = c_parser_initializer (parser, omp_priv);
> finish_init ();
> finish_decl (omp_priv, loc, init.value,
> init.original_type, NULL_TREE);
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 70ad681467e..ff56fddba54 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -8253,6 +8253,14 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
> && !TYPE_REF_P (type))
> TREE_CONSTANT (decl) = 1;
> }
> + /* This is handled mostly by gimplify.cc, but we have to deal with
> + not warning about int x = x; as it is a GCC extension to turn off
> + this warning but only if warn_init_self is zero. */
> + if (!DECL_EXTERNAL (decl)
> + && !TREE_STATIC (decl)
> + && decl == tree_strip_any_location_wrapper (init)
> + && !warn_init_self)
> + suppress_warning (decl, OPT_Winit_self);
> }
>
> if (flag_openmp
> diff --git a/gcc/testsuite/c-c++-common/Winit-self1.c b/gcc/testsuite/c-c++-common/Winit-self1.c
> new file mode 100644
> index 00000000000..740b83b5e9f
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/Winit-self1.c
> @@ -0,0 +1,31 @@
> +/* PR middle-end/102633 */
> +/* { dg-do compile } */
> +/* { dg-options "-Wuninitialized -Wno-init-self" } */
> +
> +int
> +fn1 (void)
> +{
> + int i = i;
> + return i;
> +}
> +
> +int
> +fn2 ()
> +{
> + const int j = j;
> + return j;
> +}
> +
> +int
> +fn3 ()
> +{
> + volatile int k = k;
> + return k;
> +}
> +
> +int
> +fn4 ()
> +{
> + const volatile int l = l;
> + return l;
> +}
> diff --git a/gcc/testsuite/c-c++-common/Winit-self2.c b/gcc/testsuite/c-c++-common/Winit-self2.c
> new file mode 100644
> index 00000000000..13aa9efdf26
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/Winit-self2.c
> @@ -0,0 +1,31 @@
> +/* PR middle-end/102633 */
> +/* { dg-do compile } */
> +/* { dg-options "-Wuninitialized -Winit-self" } */
> +
> +int
> +fn1 (void)
> +{
> + int i = i; /* { dg-warning "used uninitialized" } */
> + return i;
> +}
> +
> +int
> +fn2 ()
> +{
> + const int j = j; /* { dg-warning "used uninitialized" } */
> + return j;
> +}
> +
> +int
> +fn3 ()
> +{
> + volatile int k = k; /* { dg-warning "used uninitialized" } */
> + return k;
> +}
> +
> +int
> +fn4 ()
> +{
> + const volatile int l = l; /* { dg-warning "used uninitialized" } */
> + return l;
> +}
>
> base-commit: 21c7aab09805d0c8c7695c8a69c8715d673a739a
next prev parent reply other threads:[~2022-08-11 2:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-26 19:03 [PATCH] " Marek Polacek
2022-07-26 20:24 ` Jason Merrill
2022-07-26 21:31 ` Marek Polacek
2022-08-06 22:29 ` Jason Merrill
2022-08-08 19:06 ` [PATCH v2] " Marek Polacek
2022-08-11 2:05 ` Jason Merrill [this message]
2022-08-11 22:30 ` Jason Merrill
2022-07-27 6:41 ` [PATCH] " Richard Biener
2022-07-27 11:37 ` Marek Polacek
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=c7d80080-02ca-2880-1826-db83ecdc1964@redhat.com \
--to=jason@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=joseph@codesourcery.com \
--cc=polacek@redhat.com \
--cc=rguenther@suse.de \
/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).