[Bug c/97986] New: ICE in force_constant_size when applying va_arg to VLA type

[Bug c/97986] New: ICE in force_constant_size when applying va_arg to VLA type

[pascal_cuoq at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

            Bug ID: 97986
           Summary: ICE in force_constant_size when applying va_arg to VLA
                    type
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pascal_cuoq at hotmail dot com
  Target Milestone: ---

This bug seems most similar to (but still different from)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59711 (in which a comment says
that it appears to have been fixed in GCC 6).

In GCC 10.2 and some earlier versions, compiling the following program
(Compiler Explorer link: https://gcc.godbolt.org/z/11ob5j ):

#include <stdarg.h>

int sum(int n, ...)
{
    va_list ap;
    va_start(ap, n);
    int *input = va_arg(ap, int[n]);
    int rc = 0;
    for (int i = 0; i < n; i++)
        rc += input[i];
    return rc;
}

Produces the following error message:

In file included from <source>:1:
<source>: In function 'sum':
<source>:7:29: internal compiler error: in force_constant_size, at
gimplify.c:733
    7 |     int *input = va_arg(ap, int[n]);
      |                             ^~~
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1

[Bug c/97986] ICE in force_constant_size when applying va_arg to VLA type

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

--- Comment #1 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
I guess this should be handled like va_arg for float: give a warning about 
the type passed, then generate an abort (making sure that side-effects in 
both arguments take effect before the abort, in case a side-effect 
involves calling longjmp or exit).

(Technically a fixed-size array type argument to va_arg could be used in 
C90 mode to retrieve a non-lvalue array passed by value as a function 
argument, but the result would just be another non-lvalue array with no 
way to access the array elements, so just as useless as all other cases of 
non-lvalue arrays in C90.  So although specifying any array type as the 
second argument to va_arg is very dubious, maybe the case of a non-VLA in 
C90 mode should not generate an abort.)

[Bug c/97986] [9/10/11/12 Regression] ICE in force_constant_size when applying va_arg to VLA type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code,
                   |                            |needs-bisection
   Last reconfirmed|                            |2022-01-03
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
            Summary|ICE in force_constant_size  |[9/10/11/12 Regression] ICE
                   |when applying va_arg to VLA |in force_constant_size when
                   |type                        |applying va_arg to VLA type

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, This ICE started in GCC 6 even.

[Bug c/97986] [9/10/11/12 Regression] ICE in force_constant_size when applying va_arg to VLA type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |9.5

[Bug c/97986] [9/10/11/12 Regression] ICE in force_constant_size when applying va_arg to VLA type

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

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

[Bug c/97986] [9/10/11/12 Regression] ICE in force_constant_size when applying va_arg to VLA type since r6-91-gf8e89441bc5518f4

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |vries at gcc dot gnu.org
            Summary|[9/10/11/12 Regression] ICE |[9/10/11/12 Regression] ICE
                   |in force_constant_size when |in force_constant_size when
                   |applying va_arg to VLA type |applying va_arg to VLA type
                   |                            |since
                   |                            |r6-91-gf8e89441bc5518f4
           Keywords|needs-bisection             |

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r6-91-gf8e89441bc5518f4.

[Bug c/97986] [10/11/12/13 Regression] ICE in force_constant_size when applying va_arg to VLA type since r6-91-gf8e89441bc5518f4

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.5                         |10.4

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9 branch is being closed

[Bug c/97986] [10/11/12/13 Regression] ICE in force_constant_size when applying va_arg to VLA type since r6-91-gf8e89441bc5518f4

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.4                        |10.5

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 10.4 is being released, retargeting bugs to GCC 10.5.

[Bug c/97986] [11/12/13/14 Regression] ICE in force_constant_size when applying va_arg to VLA type since r6-91-gf8e89441bc5518f4

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97986

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.