[Bug c/111811] New: gcc: internal compiler error: tree check: expected none of vector_type, have vector_type in finish_struct

[Bug c/111811] New: gcc: internal compiler error: tree check: expected none of vector_type, have vector_type in finish_struct

[congli at smail dot nju.edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

            Bug ID: 111811
           Summary: gcc: internal compiler error: tree check: expected
                    none of vector_type, have vector_type in finish_struct
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: congli at smail dot nju.edu.cn
  Target Milestone: ---

Compiler explorer: https://godbolt.org/z/WWzcPWcqs.

The following program `small.c` triggers a crash in gcc-14:

``` sh
% cat small.c
struct A {
    __attribute__((__vector_size__(4))) float d : 1;
};


% gcc-tk -O0 small.c
<source>:2:47: error: bit-field 'd' has invalid type
    2 |     __attribute__((__vector_size__(4))) float d : 1;
      |                                               ^
<source>:3:1: internal compiler error: tree check: expected none of
vector_type, have vector_type in finish_struct, at c/c-decl.cc:9358
    3 | };
      | ^
0x22ff3ee internal_error(char const*, ...)
  ???:0
0x8a7b87 tree_not_check_failed(tree_node const*, char const*, int, char const*,
...)
  ???:0
0xa7ab0d c_parser_declspecs(c_parser*, c_declspecs*, bool, bool, bool, bool,
bool, bool, bool, c_lookahead_kind)
  ???:0
0xaa468d c_parse_file()
  ???:0
0xb17919 c_common_parse_file()
  ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```

GCC version:

```
gcc
(Compiler-Explorer-Build-gcc-300d7d3a8f4b53d045ce43f1ed4e10301781c786-binutils-2.40)
14.0.0 20231014 (experimental)
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-11-12
            Summary|ICE with vector float       |[14 Regression] ICE with
                   |bitfield after error        |vector float bitfield after
                   |                            |error
                 CC|                            |pinskia at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
   Target Milestone|---                         |14.0

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
      if (TREE_CODE (field) == FIELD_DECL
          && DECL_INITIAL (field)
          && TREE_TYPE (field) != error_mark_node)
        {
          unsigned HOST_WIDE_INT width
            = tree_to_uhwi (DECL_INITIAL (field));
          tree type = TREE_TYPE (field);
          if (width != TYPE_PRECISION (type)) <--- Crash
            {

Obvious introduced by the TYPE_PRECISION change to ICE on vector types:
r14-2150-gfe48f2651334bc

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
But we should also be rejecting:
```
struct A {
    __attribute__((__vector_size__(4))) int d : 1;
};

struct A b = {0};
```
Which we currently accepts before and ICE now.

Note for the float case, we could in theory change:
```
  /* Detect invalid bit-field type.  */
  if (TREE_CODE (*type) != INTEGER_TYPE
      && TREE_CODE (*type) != BOOLEAN_TYPE
      && TREE_CODE (*type) != ENUMERAL_TYPE
      && TREE_CODE (*type) != BITINT_TYPE)
    {
      error_at (loc, "bit-field %qs has invalid type", name);
      *type = unsigned_type_node;
    }

```
to use error_mark_node instead of unsigned_type_node here and that would fix
the ICE for the original testcase but not the above testcase.

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
I agree, this shouldn't be a valid bit-field type.  We apply the vector_size
attribute before parsing/applying :1.  There must be code to reject
float : 1, not sure where that is.

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

--- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
The checks are in check_bitfield_type_and_width.  I expect the attribute - 
in this position a declaration attribute - gets applied after that (and 
while applying it results in a change to the type, and thus in the 
declaration being laid out again, this check doesn't get repeated).

In this case, the existing check is correct but not sufficient.  In 
another case the check is arguably too early:

struct s { int __attribute__ ((__mode__ (DI))) x : 50; };

Considering int __attribute__ ((__mode__ (DI))) as a DImode integer type, 
that bit-field width is valid - but it's rejected because the check is 
carried out on int, before the attribute gets applied.  Getting that case 
to work might require extracting early those declaration attributes that 
actually affect the type, so they can be applied to the type before the 
declaration gets constructed and such checks are carried out.

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 13 Nov 2023, joseph at codesourcery dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811
> 
> --- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
> The checks are in check_bitfield_type_and_width.  I expect the attribute - 
> in this position a declaration attribute - gets applied after that (and 
> while applying it results in a change to the type, and thus in the 
> declaration being laid out again, this check doesn't get repeated).
> 
> In this case, the existing check is correct but not sufficient.  In 
> another case the check is arguably too early:
> 
> struct s { int __attribute__ ((__mode__ (DI))) x : 50; };
> 
> Considering int __attribute__ ((__mode__ (DI))) as a DImode integer type, 
> that bit-field width is valid - but it's rejected because the check is 
> carried out on int, before the attribute gets applied.  Getting that case 
> to work might require extracting early those declaration attributes that 
> actually affect the type, so they can be applied to the type before the 
> declaration gets constructed and such checks are carried out.

Ah, and when applying the vector_size attribute the FIELD_DECL hasn't been
updated to indicate we identified it as bitfield (so we could reject
the attribute) ...

I'll leave this to frontend folks to sort out.

[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4

[Bug c/111811] [14/15 Regression] ICE with vector float bitfield after error

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|14.0                        |14.2

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 14.1 is being released, retargeting bugs to GCC 14.2.