Re: [PATCH v2] Skip VLA structure field tests when compiling with clang

[Luis Machado <luis.machado@linaro.org>]

Hi Gary,

On 7/8/20 12:46 PM, Gary Benson wrote:
> Hi Luis,
> 
> Luis Machado wrote:
>> As a general comment (for this and other patches like this), I think
>> the preprocessor blocks intermixed with the test code make it harder
>> to follow and update the test.
>>
>> If clang claims it will never support a particular feature, then
>> maybe we should ... separate the bits clang doesn't support and put
>> it into a separate test that clang-compiled hosts should skip?
> 
> Thanks for the review.  I've made that change, the updated patch is
> below.  I checked it on Fedora 31 x86_64, GCC and clang.  Is it ok to
> commit?

Thanks. That looks cleaner. Just a gotcha below...

> 
> Cheers
> Gary
> 
> --
> Clang fails to compile gdb.base/vla-datatypes.c with the following
> error: fields must have a constant size: 'variable length array in
> structure' extension will never be supported.  This patch factors
> the affected tests out into a new testcase, vla-struct-fields.{exp,c},
> which is skipped when the testcase is compiled using clang,
> 
> gdb/testsuite/ChangeLog:
> 
> 	* gdb.base/vla-datatypes.c (vla_factory): Factor out sections
> 	defining and using VLA structure fields into...
> 	* gdb.base/vla-struct-fields.c: New file.
> 	* gdb.base/vla-datatypes.exp: Factor out VLA structure field
> 	tests into...
> 	* gdb.base/vla-struct-fields.exp: New file.
> ---
>   gdb/testsuite/ChangeLog                      |   9 +++
>   gdb/testsuite/gdb.base/vla-datatypes.c       |  53 --------------
>   gdb/testsuite/gdb.base/vla-datatypes.exp     |  24 -------
>   gdb/testsuite/gdb.base/vla-struct-fields.c   | 104 +++++++++++++++++++++++++++
>   gdb/testsuite/gdb.base/vla-struct-fields.exp |  67 +++++++++++++++++
>   5 files changed, 180 insertions(+), 77 deletions(-)
>   create mode 100644 gdb/testsuite/gdb.base/vla-struct-fields.c
>   create mode 100644 gdb/testsuite/gdb.base/vla-struct-fields.exp
> 
> diff --git a/gdb/testsuite/gdb.base/vla-datatypes.c b/gdb/testsuite/gdb.base/vla-datatypes.c
> index 682319f..d8b835a 100644
> --- a/gdb/testsuite/gdb.base/vla-datatypes.c
> +++ b/gdb/testsuite/gdb.base/vla-datatypes.c
> @@ -46,49 +46,6 @@ struct foo
>     BAR             bar_vla[n];
>     int i;
>   
> -  struct vla_struct
> -  {
> -    int something;
> -    int vla_field[n];
> -  };
> -  /* Define a typedef for a VLA structure.  */
> -  typedef struct vla_struct vla_struct_typedef;
> -  vla_struct_typedef vla_struct_object;
> -
> -  struct inner_vla_struct
> -  {
> -    int something;
> -    int vla_field[n];
> -    int after;
> -  } inner_vla_struct_object;
> -
> -  /* Define a structure which uses a typedef for the VLA field
> -     to make sure that GDB creates the proper type for this field,
> -     preventing a possible assertion failure (see gdb/21356).  */
> -  struct vla_struct_typedef_struct_member
> -  {
> -    int something;
> -    vla_struct_typedef vla_object;
> -  } vla_struct_typedef_struct_member_object;
> -
> -  union vla_union
> -  {
> -    int vla_field[n];
> -  } vla_union_object;
> -
> -  /* Like vla_struct_typedef_struct_member but a union type.  */
> -  union vla_struct_typedef_union_member
> -  {
> -    int something;
> -    vla_struct_typedef vla_object;
> -  } vla_struct_typedef_union_member_object;
> -
> -  vla_struct_object.something = n;
> -  inner_vla_struct_object.something = n;
> -  inner_vla_struct_object.after = n;
> -  vla_struct_typedef_struct_member_object.something = n * 2;
> -  vla_struct_typedef_struct_member_object.vla_object.something = n * 3;
> -  vla_struct_typedef_union_member_object.vla_object.something = n + 1;
>     for (i = 0; i < n; i++)
>       {
>         int_vla[i] = i*2;
> @@ -104,13 +61,6 @@ struct foo
>         foo_vla[i].a = i*2;
>         bar_vla[i].x = i*2;
>         bar_vla[i].y.a = i*2;
> -      vla_struct_object.vla_field[i] = i*2;
> -      vla_union_object.vla_field[i] = i*2;
> -      inner_vla_struct_object.vla_field[i] = i*2;
> -      vla_struct_typedef_struct_member_object.vla_object.vla_field[i]
> -	= i * 3;
> -      vla_struct_typedef_union_member_object.vla_object.vla_field[i]
> -	= i * 3 - 1;
>       }
>   
>     size_t int_size        = sizeof(int_vla);     /* vlas_filled */
> @@ -124,9 +74,6 @@ struct foo
>     size_t uchar_size      = sizeof(unsigned_char_vla);
>     size_t foo_size        = sizeof(foo_vla);
>     size_t bar_size        = sizeof(bar_vla);
> -  size_t vla_struct_object_size = sizeof(vla_struct_object);
> -  size_t vla_union_object_size = sizeof(vla_union_object);
> -  size_t inner_vla_struct_object_size = sizeof(inner_vla_struct_object);
>   
>     return;                                 /* break_end_of_vla_factory */
>   }
> diff --git a/gdb/testsuite/gdb.base/vla-datatypes.exp b/gdb/testsuite/gdb.base/vla-datatypes.exp
> index e8d8457..201f051 100644
> --- a/gdb/testsuite/gdb.base/vla-datatypes.exp
> +++ b/gdb/testsuite/gdb.base/vla-datatypes.exp
> @@ -41,14 +41,6 @@ gdb_test "print foo_vla" \
>            "\\\{\\\{a = 0\\\}, \\\{a = 2\\\}, \\\{a = 4\\\}, \\\{a = 6\\\}, \\\{a = 8\\\}\\\}"
>   gdb_test "print bar_vla" \
>            "\\\{\\\{x = 0, y = \\\{a = 0\\\}\\\}, \\\{x = 2, y = \\\{a = 2\\\}\\\}, \\\{x = 4, y = \\\{a = 4\\\}\\\}, \\\{x = 6, y = \\\{a = 6\\\}\\\}, \\\{x = 8, y = \\\{a = 8\\\}\\\}\\\}"
> -gdb_test "print vla_struct_object" \
> -    "\\\{something = 5, vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
> -gdb_test "print vla_union_object" \
> -    "\\\{vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
> -gdb_test "print vla_struct_typedef_struct_member_object" \
> -    "\\\{something = 10, vla_object = \\\{something = 15, vla_field = \\\{0, 3, 6, 9, 12\\\}\\\}\\\}"
> -gdb_test "print vla_struct_typedef_union_member_object" \
> -    "\\\{something = 6, vla_object = \\\{something = 6, vla_field = \\\{-1, 2, 5, 8, 11\\\}\\\}\\\}"
>   
>   # Check whatis of VLA's.
>   gdb_test "whatis int_vla" "type = int \\\[5\\\]"
> @@ -65,8 +57,6 @@ gdb_test "whatis unsigned_short_vla" \
>   gdb_test "whatis unsigned_char_vla" "type = unsigned char \\\[5\\\]"
>   gdb_test "whatis foo_vla" "type = struct foo \\\[5\\\]"
>   gdb_test "whatis bar_vla" "type = BAR \\\[5\\\]"
> -gdb_test "whatis vla_struct_object" "type = vla_struct_typedef"
> -gdb_test "whatis vla_union_object" "type = union vla_union"
>   
>   # Check ptype of VLA's.
>   gdb_test "ptype int_vla" "type = int \\\[5\\\]"
> @@ -82,10 +72,6 @@ gdb_test "ptype unsigned_char_vla" "type = unsigned char \\\[5\\\]"
>   gdb_test "ptype foo_vla" "type = struct foo {\r\n\\s+int a;\r\n} \\\[5\\\]"
>   gdb_test "ptype bar_vla" \
>            "type = struct bar {\r\n\\s+int x;\r\n\\s+struct foo y;\r\n} \\\[5\\\]"
> -gdb_test "ptype vla_struct_object" \
> -    "type = struct vla_struct {\r\n\\s+int something;\r\n\\s+int vla_field\\\[5\\\];\r\n}"
> -gdb_test "ptype vla_union_object" \
> -    "type = union vla_union {\r\n\\s+int vla_field\\\[5\\\];\r\n}"
>   
>   # Check the size of the VLA's.
>   gdb_breakpoint [gdb_get_line_number "break_end_of_vla_factory"]
> @@ -109,10 +95,6 @@ gdb_test "print uchar_size == sizeof(unsigned_char_vla)" " = 1" \
>            "size of unsigned_char_vla"
>   gdb_test "print foo_size == sizeof(foo_vla)" " = 1" "size of foo_vla"
>   gdb_test "print bar_size == sizeof(bar_vla)" " = 1" "size of bar_vla"
> -gdb_test "print vla_struct_object_size == sizeof(vla_struct_object)" \
> -    " = 1" "size of vla_struct_object"
> -gdb_test "print vla_union_object_size == sizeof(vla_union_object)" \
> -    " = 1" "size of vla_union_object"
>   
>   # Check side effects for sizeof argument.
>   set sizeof_int [get_sizeof "int" 4]
> @@ -130,9 +112,3 @@ gdb_test "print int_vla\[0\]" " = 42" \
>   gdb_test "whatis ++int_vla\[0\]" "type = int"
>   gdb_test "print int_vla\[0\]" " = 42" \
>            "print int_vla\[0\] - whatis no side effects"
> -
> -# Fails due to incorrect debugging information generated by GCC.
> -setup_xfail "*-*-*"
> -gdb_test \
> -    "print inner_vla_struct_object_size == sizeof(inner_vla_struct_object)" \
> -    " = 1" "size of inner_vla_struct_object"
> diff --git a/gdb/testsuite/gdb.base/vla-struct-fields.c b/gdb/testsuite/gdb.base/vla-struct-fields.c
> new file mode 100644
> index 0000000..ef236a7
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/vla-struct-fields.c
> @@ -0,0 +1,104 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2014-2020 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <stddef.h>
> +#define SIZE 5
> +
> +struct foo
> +{
> +  int a;
> +};
> +
> +typedef struct bar
> +{
> +  int x;
> +  struct foo y;
> +} BAR;
> +
> +void
> +vla_factory (int n)
> +{
> +  struct vla_struct
> +  {
> +    int something;
> +    int vla_field[n];
> +  };
> +  /* Define a typedef for a VLA structure.  */
> +  typedef struct vla_struct vla_struct_typedef;
> +  vla_struct_typedef vla_struct_object;
> +
> +  struct inner_vla_struct
> +  {
> +    int something;
> +    int vla_field[n];
> +    int after;
> +  } inner_vla_struct_object;
> +
> +  /* Define a structure which uses a typedef for the VLA field
> +     to make sure that GDB creates the proper type for this field,
> +     preventing a possible assertion failure (see gdb/21356).  */
> +  struct vla_struct_typedef_struct_member
> +  {
> +    int something;
> +    vla_struct_typedef vla_object;
> +  } vla_struct_typedef_struct_member_object;
> +
> +  union vla_union
> +  {
> +    int vla_field[n];
> +  } vla_union_object;
> +
> +  /* Like vla_struct_typedef_struct_member but a union type.  */
> +  union vla_struct_typedef_union_member
> +  {
> +    int something;
> +    vla_struct_typedef vla_object;
> +  } vla_struct_typedef_union_member_object;
> +  int i;
> +
> +  vla_struct_object.something = n;
> +  inner_vla_struct_object.something = n;
> +  inner_vla_struct_object.after = n;
> +  vla_struct_typedef_struct_member_object.something = n * 2;
> +  vla_struct_typedef_struct_member_object.vla_object.something = n * 3;
> +  vla_struct_typedef_union_member_object.vla_object.something = n + 1;
> +
> +  for (i = 0; i < n; i++)
> +    {
> +      vla_struct_object.vla_field[i] = i*2;
> +      vla_union_object.vla_field[i] = i*2;
> +      inner_vla_struct_object.vla_field[i] = i*2;
> +      vla_struct_typedef_struct_member_object.vla_object.vla_field[i]
> +	= i * 3;
> +      vla_struct_typedef_union_member_object.vla_object.vla_field[i]
> +	= i * 3 - 1;
> +    }
> +
> +  size_t vla_struct_object_size
> +    = sizeof(vla_struct_object);          /* vlas_filled */
> +  size_t vla_union_object_size = sizeof(vla_union_object);
> +  size_t inner_vla_struct_object_size = sizeof(inner_vla_struct_object);
> +
> +  return;                                 /* break_end_of_vla_factory */
> +}
> +
> +int
> +main (void)
> +{
> +  vla_factory(SIZE);
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/vla-struct-fields.exp b/gdb/testsuite/gdb.base/vla-struct-fields.exp
> new file mode 100644
> index 0000000..150a328
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/vla-struct-fields.exp
> @@ -0,0 +1,67 @@
> +# Copyright 2014-2020 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +standard_testfile
> +
> +# Clang says it will never support variable length arrays in structures.
> +if {[test_compiler_info clang*]} {
> +    unsupported "compiler does not variable length arrays in structure"

                                       ^^^ support?

Otherwise this looks good to me. Can't approve a commit though.