[Bug c/101289] New: bogus -Wvla-paramater warning when using const for vla param

[Bug c/101289] New: bogus -Wvla-paramater warning when using const for vla param

[ljrk at ljrk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

            Bug ID: 101289
           Summary: bogus -Wvla-paramater warning when using const for vla
                    param
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ljrk at ljrk dot org
  Target Milestone: ---

Created attachment 51099
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51099&action=edit
minimum working/reproducing example

If the vla parameter has a const specifier, the compiler will warn about
mismatched bounds:

$ cat mwe.c && make CFLAGS=-Wvla-parameter mwe.o     
extern void mwe(const int len, char buf[len]);
void mwe(const int len, char buf[len]) {}
cc -Wvla-parameter   -c -o mwe.o mwe.c
mwe.c:2:30: warning: argument 2 of type ‘char[len]’ declared with mismatched
bound ‘len’ [-Wvla-parameter]
    2 | void mwe(const int len, char buf[len]) {}
      |                         ~~~~~^~~~~~~~
mwe.c:1:37: note: previously declared as ‘char[len]’ with bound ‘len’
    1 | extern void mwe(const int len, char buf[len]);
      |                                ~~~~~^~~~~~~~
$

If I remove the const specifier to len, the warning goes away:

$ sed 's/const //g' -i mwe.c && make CFLAGS=-Wvla-parameter mwe.o  
cc -Wvla-parameter   -c -o mwe.o mwe.c
$

Maybe this is related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97548 ?

[Bug c/101289] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.2
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
                 CC|                            |msebor at gcc dot gnu.org
   Last reconfirmed|                            |2021-07-01

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed.  The root cause is the same as in pr97548 even though the test case
here is quite different.  They're both worth adding to the test suite.

[Bug c/101289] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
         Depends on|                            |97548
             Status|NEW                         |ASSIGNED


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97548
[Bug 97548] bogus -Wvla-parameter on a bound expression involving a parameter

[Bug c/101289] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
      Known to fail|                            |11.1.0, 12.0

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/574310.html

[Bug c/101289] bogus -Wvla-paramater warning when using const for vla param

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Sebor <msebor@gcc.gnu.org>:

https://gcc.gnu.org/g:98f1f9f38c45218c06200feb1939c9433a2ab6ca

commit r12-2329-g98f1f9f38c45218c06200feb1939c9433a2ab6ca
Author: Martin Sebor <msebor@redhat.com>
Date:   Thu Jul 15 10:11:23 2021 -0600

    Avoid -Wvla-parameter for nontrivial bounds [PR97548].

    Resolves:
    PR c/101289 - bogus -Wvla-paramater warning when using const for vla param
    PR c/97548 -  bogus -Wvla-parameter on a bound expression involving a
parameter

    gcc/c-family/ChangeLog:

            PR c/101289
            PR c/97548
            * c-warn.c (warn_parm_array_mismatch): Use OEP_DECL_NAME.

    gcc/c/ChangeLog:

            PR c/101289
            PR c/97548
            * c-decl.c (get_parm_array_spec): Strip nops.

    gcc/ChangeLog:

            PR c/101289
            PR c/97548
            * fold-const.c (operand_compare::operand_equal_p): Handle
OEP_DECL_NAME.
            (operand_compare::verify_hash_value): Same.
            * tree-core.h (OEP_DECL_NAME): New.

    gcc/testsuite/ChangeLog:

            * gcc.dg/Wvla-parameter-12.c: New test.

[Bug c/101289] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|12.0                        |

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Fixed for GCC 12.0.

[Bug c/101289] [11 Regression] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|bogus -Wvla-paramater       |[11 Regression] bogus
                   |warning when using const    |-Wvla-paramater warning
                   |for vla param               |when using const for vla
                   |                            |param

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
I'll backport the patch into GCC 11.

[Bug c/101289] [11 Regression] bogus -Wvla-paramater warning when using const for vla param

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.2                        |11.3

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11.2 is being released, retargeting bugs to GCC 11.3

[Bug c/101289] [11 Regression] bogus -Wvla-paramater warning when using const for vla param

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Martin Sebor
<msebor@gcc.gnu.org>:

https://gcc.gnu.org/g:7d3f53c595e1766ca0494e5f56f33b0ce49b3bb4

commit r11-9396-g7d3f53c595e1766ca0494e5f56f33b0ce49b3bb4
Author: Martin Sebor <msebor@redhat.com>
Date:   Thu Jul 15 10:11:23 2021 -0600

    Avoid -Wvla-parameter for nontrivial bounds [PR97548].

    Resolves:
    PR c/101289 - bogus -Wvla-paramater warning when using const for vla param
    PR c/97548 -  bogus -Wvla-parameter on a bound expression involving a
parameter

    gcc/c-family/ChangeLog:

            PR c/101289
            PR c/97548
            * c-warn.c (warn_parm_array_mismatch): Use OEP_DECL_NAME.

    gcc/c/ChangeLog:

            PR c/101289
            PR c/97548
            * c-decl.c (get_parm_array_spec): Strip nops.

    gcc/ChangeLog:

            PR c/101289
            PR c/97548
            * fold-const.c (operand_compare::operand_equal_p): Handle
OEP_DECL_NAME.
            (operand_compare::verify_hash_value): Same.
            * tree-core.h (OEP_DECL_NAME): New.

    gcc/testsuite/ChangeLog:

            * gcc.dg/Wvla-parameter-12.c: New test.

[Bug c/101289] [11 Regression] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

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

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

--- Comment #8 from Martin Sebor <msebor at gcc dot gnu.org> ---
Fixed.

[Bug c/101289] [11 Regression] bogus -Wvla-paramater warning when using const for vla param

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289
Bug 101289 depends on bug 97548, which changed state.

Bug 97548 Summary: [11 Regression] bogus -Wvla-parameter on a bound expression involving a parameter
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97548

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