[Bug middle-end/102633] New: warning for self-initialization despite -Wno-init-self

[Bug middle-end/102633] New: warning for self-initialization despite -Wno-init-self

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

            Bug ID: 102633
           Summary: warning for self-initialization despite -Wno-init-self
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

GCC issues -Wuninitialized for cv-qualified variables initialized with
themselves even when -Wno-init-self is in effect.

$ cat x.c && gcc -O2 -S -Wall -Wno-init-self -xc++ x.c
int f (void)
{
  int i = i;           // no warning (good)
  return i;
}

int g (void)
{
  const int i = i;     // -Wuninitialized (bug)
  return i;
}

int h (void)
{
  volatile int i = i;  // -Wuninitialized (bug)
  return i;
}

x.c: In function ‘int g()’:
x.c:9:13: warning: ‘i’ is used uninitialized [-Wuninitialized]
    9 |   const int i = i;     // -Wuninitialized (bug)
      |             ^
x.c:9:13: note: ‘i’ was declared here
    9 |   const int i = i;     // -Wuninitialized (bug)
      |             ^
x.c: In function ‘int h()’:
x.c:15:20: warning: ‘i’ is used uninitialized [-Wuninitialized]
   15 |   volatile int i = i;  // -Wuninitialized (bug)
      |                    ^
x.c:15:16: note: ‘i’ declared here
   15 |   volatile int i = i;  // -Wuninitialized (bug)
      |                ^

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|warning for                 |[11/12 Regression] warning
                   |self-initialization despite |for self-initialization
                   |-Wno-init-self              |despite -Wno-init-self
           Keywords|                            |diagnostic
             Blocks|                            |24639

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The suppression has worked until GCC 10.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639
[Bug 24639] [meta-bug] bug to track all Wuninitialized issues

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |muecker at gwdg dot de

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Bisection points to g:32934a4f45a72144cdcd0712cc294fe88c36f13d.

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.3

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.3                        |11.4

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11.3 is being released, retargeting bugs to GCC 11.4.

[Bug middle-end/102633] [11/12/13 Regression] warning for self-initialization despite -Wno-init-self

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-07-26
           Priority|P3                          |P2

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Re-confirmed.  For volatiles whether they are uninitialized ever is a separate
question...

Martin - can you try addressing bugs your changes cause?

[Bug middle-end/102633] [11/12/13 Regression] warning for self-initialization despite -Wno-init-self

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The problem is that since the patch above, we create a NOP_EXPR:

 2172   if (convert_p && !error_operand_p (exp.value)
 2173       && (TREE_CODE (TREE_TYPE (exp.value)) != ARRAY_TYPE))
 2174     exp.value = convert (build_qualified_type (TREE_TYPE (exp.value),
TYPE_UNQUALIFIED), exp.value);

so the DECL_INITIAL is '(int) i' and not 'i' anymore.  Then we don't
suppress_warning here:

711     case DECL_EXPR:
712       /* This is handled mostly by gimplify.cc, but we have to deal with
713          not warning about int x = x; as it is a GCC extension to turn off
714          this warning but only if warn_init_self is zero.  */
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.

[Bug middle-end/102633] [11/12/13 Regression] warning for self-initialization despite -Wno-init-self

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Patch:

--- a/gcc/c-family/c-gimplify.cc
+++ b/gcc/c-family/c-gimplify.cc
@@ -712,13 +712,17 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p
ATTRIBUTE_UNUSED,
       /* 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;
+      {
+   tree &decl = DECL_EXPR_DECL (*expr_p);
+   if (VAR_P (decl)
+       && !DECL_EXTERNAL (decl)
+       && !TREE_STATIC (decl)
+       && (DECL_INITIAL (decl)
+       && tree_strip_nop_conversions (DECL_INITIAL (decl)) == decl)
+       && !warn_init_self)
+     suppress_warning (decl, OPT_Winit_self);
+   break;
+      }

     case PREINCREMENT_EXPR:
     case PREDECREMENT_EXPR:

[Bug middle-end/102633] [11/12/13 Regression] warning for self-initialization despite -Wno-init-self

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

--- Comment #7 from Martin Uecker <muecker at gwdg dot de> ---
Sorry, somehow I missed this. I will look at this once I am back from travel
(if Marek hasen't fixed it)

[Bug middle-end/102633] [11/12/13 Regression] warning for self-initialization despite -Wno-init-self

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:04ce2400b35225302e0d6883bb0817378180f5d7

commit r13-2022-g04ce2400b35225302e0d6883bb0817378180f5d7
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jul 26 13:55:58 2022 -0400

    c-family: Honor -Wno-init-self for cv-qual vars [PR102633]

    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.

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
            Summary|[11/12/13 Regression]       |[11/12 Regression] warning
                   |warning for                 |for self-initialization
                   |self-initialization despite |despite -Wno-init-self
                   |-Wno-init-self              |
             Status|ASSIGNED                    |RESOLVED

--- Comment #9 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed on trunk.  Not sure about backporting this.

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Will try to backport to 12 in order to unblock bug 105593.

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:aabebf76e9d9a805ea5b443d4ee4f49f13155d87

commit r12-9160-gaabebf76e9d9a805ea5b443d4ee4f49f13155d87
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jul 26 13:55:58 2022 -0400

    c-family: Honor -Wno-init-self for cv-qual vars [PR102633]

    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.

    (cherry picked from commit 04ce2400b35225302e0d6883bb0817378180f5d7)

[Bug middle-end/102633] [11/12 Regression] warning for self-initialization despite -Wno-init-self

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for gcc 12.3 too.

[Bug middle-end/102633] [11 Regression] warning for self-initialization despite -Wno-init-self

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102633

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #13 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
.