[Bug c++/101833] New: [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[Bug c++/101833] New: [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

            Bug ID: 101833
           Summary: [9/10/11/12 Regression] ICE with -Wformat on a
                    constructor with a virtual base
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
class Base {};
struct VDerived : virtual Base
{
                VDerived(int x, const char * f, ...)
__attribute__((format(printf, 5, 6)));
}  a(1, "%s %d", "foo", 1);
----- CUT ----
We get an ICE:
<source>:5:26: warning: 'format' attribute argument 2 value '5' exceeds the
number of function parameters 3 [-Wattributes]
    5 | }  a(1, "%s %d", "foo", 1);
      |                          ^
<source>:5:26: internal compiler error: in get_constant, at
c-family/c-format.c:325
0x1dbb089 internal_error(char const*, ...)

This started in 9.1.0

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |9.1.0
   Target Milestone|---                         |9.5
      Known to work|                            |8.5.0

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |msebor at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-10
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r9-4163-g1d24950977c730f5.
What's strange that one needs '-Wall' in order to trigger the warning.
-Wattributes is not enough, is it correct Martin?

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |10.3.0, 11.2.0, 12.0

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning is issued when the declaration is seen (either with -Wall or with
just -Wattributes).  The ICE is a side-effect of -Wformat checking calls to the
function.

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

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

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

[Bug c++/101833] [9/10/11/12/13 Regression] ICE with -Wformat on a constructor with a virtual base

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

--- Comment #3 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:0c723bb4be2a67657828b692997855afcdc5d286

commit r13-167-g0c723bb4be2a67657828b692997855afcdc5d286
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Mar 31 18:31:39 2022 -0400

    c, c++: attribute format on a ctor with a vbase [PR101833, PR47634]

    Attribute format takes three arguments: archetype, string-index, and
    first-to-check.  The last two specify the position in the function
    parameter list.  r63030 clarified that "Since non-static C++ methods have
    an implicit this argument, the arguments of such methods should be counted
    from two, not one, when giving values for string-index and first-to-check."
    Therefore one has to write

      struct D {
        D(const char *, ...) __attribute__((format(printf, 2, 3)));
      };

    However -- and this is the problem in this PR -- ctors with virtual
    bases also get two additional parameters: the in-charge parameter and
    the VTT parameter (added in maybe_retrofit_in_chrg).  In fact we'll end up
    with two clones of the ctor: an in-charge and a not-in-charge version (see
    build_cdtor_clones).  That means that the argument position the user
    specified in the attribute argument will refer to different arguments,
    depending on which constructor we're currently dealing with.  This can
    cause a range of problems: wrong errors, confusing warnings, or crashes.

    This patch corrects that; for C we don't have to do anything, and in C++
    we can use num_artificial_parms_for.  It would be wrong to rewrite the
    attributes the user supplied, so I've changed POS to be passed by
    reference so that we don't have to change all the call sites of
    positional_argument and we still get the default_conversion adjustment.

    Attribute format_arg is not affected, because it requires that the
    function returns "const char *" which will never be the case for cdtors.

            PR c++/101833
            PR c++/47634

    gcc/c-family/ChangeLog:

            * c-attribs.cc (positional_argument): Pass POS by reference.  Deal
            with FN being either a function declaration or function type.  Use
            maybe_adjust_arg_pos_for_attribute.
            * c-common.cc (check_function_arguments): Maybe pass FNDECL down to
            check_function_format.
            * c-common.h (maybe_adjust_arg_pos_for_attribute): Declare.
            (positional_argument): Adjust.
            * c-format.cc (get_constant): Rename to ...
            (validate_constant): ... this.  Take EXPR by reference.  Return
bool
            instead of tree.
            (handle_format_arg_attribute): Don't overwrite FORMAT_NUM_EXPR by
the
            return value of validate_constant.
            (decode_format_attr): Don't overwrite FORMAT_NUM_EXPR and
            FIRST_ARG_NUM_EXPR by the return value of validate_constant.
            (check_function_format): Adjust a parameter name.
            (handle_format_attribute): Maybe pass FNDECL down to
decode_format_attr.

    gcc/c/ChangeLog:

            * c-objc-common.cc (maybe_adjust_arg_pos_for_attribute): New.

    gcc/cp/ChangeLog:

            * tree.cc (maybe_adjust_arg_pos_for_attribute): New.

    gcc/ChangeLog:

            * tree-core.h (struct attribute_spec): Update comment for HANDLER.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/attr-format-arg1.C: New test.
            * g++.dg/ext/attr-format1.C: New test.
            * g++.dg/ext/attr-format2.C: New test.
            * g++.dg/ext/attr-format3.C: New test.

[Bug c++/101833] [9/10/11/12 Regression] ICE with -Wformat on a constructor with a virtual base

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101833

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[9/10/11/12/13 Regression]  |[9/10/11/12 Regression] ICE
                   |ICE with -Wformat on a      |with -Wformat on a
                   |constructor with a virtual  |constructor with a virtual
                   |base                        |base
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed for GCC 13.  I don't have plans to backport this.