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

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

Hi,

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 have a separate testcase clang can actually run and skip this 
entire test if the compiler is clang?

Or maybe separate the bits clang doesn't support and put it into a 
separate test that clang-compiled hosts should skip?

On 6/30/20 8:12 AM, Gary Benson via Gdb-patches wrote:
> Hi all,
> 
> 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 adds
> preprocessor contitionals to vla-datatypes.c to not compile any code
> defining or using use VLA structure fields when compiling with clang,
> and modifies vla-datatypes.exp to skip all tests that require the
> omitted code as appropriate.
> 
> Checked on Fedora 31 x86_64, GCC and clang.  Ok to commit?
> 
> Cheers,
> Gary
> 
> --
> gdb/testsuite/ChangeLog:
> 
> 	* gdb.base/vla-datatypes.c (vla_factory): Wrap sections defining
> 	and using VLA structure fields with "#if !defined(__clang__)".
> 	* gdb.base/vla-datatypes.exp: Skip VLA structure field tests if
> 	compiling with clang.
> ---
>   gdb/testsuite/ChangeLog                  |  7 +++++
>   gdb/testsuite/gdb.base/vla-datatypes.c   |  8 ++++++
>   gdb/testsuite/gdb.base/vla-datatypes.exp | 47 ++++++++++++++++++++------------
>   3 files changed, 44 insertions(+), 18 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.base/vla-datatypes.c b/gdb/testsuite/gdb.base/vla-datatypes.c
> index 682319f..ce383a1 100644
> --- a/gdb/testsuite/gdb.base/vla-datatypes.c
> +++ b/gdb/testsuite/gdb.base/vla-datatypes.c
> @@ -46,6 +46,9 @@ struct foo
>     BAR             bar_vla[n];
>     int i;
>   
> +  /* Clang says it will never support variable length arrays in
> +     structures.  */
> +#if !defined(__clang__)
>     struct vla_struct
>     {
>       int something;
> @@ -89,6 +92,7 @@ struct foo
>     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;
> +#endif /* !defined(__clang__) */
>     for (i = 0; i < n; i++)
>       {
>         int_vla[i] = i*2;
> @@ -104,6 +108,7 @@ struct foo
>         foo_vla[i].a = i*2;
>         bar_vla[i].x = i*2;
>         bar_vla[i].y.a = i*2;
> +#if !defined(__clang__)
>         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;
> @@ -111,6 +116,7 @@ struct foo
>   	= i * 3;
>         vla_struct_typedef_union_member_object.vla_object.vla_field[i]
>   	= i * 3 - 1;
> +#endif /* !defined(__clang__) */
>       }
>   
>     size_t int_size        = sizeof(int_vla);     /* vlas_filled */
> @@ -124,9 +130,11 @@ struct foo
>     size_t uchar_size      = sizeof(unsigned_char_vla);
>     size_t foo_size        = sizeof(foo_vla);
>     size_t bar_size        = sizeof(bar_vla);
> +#if !defined(__clang__)
>     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);
> +#endif /* !defined(__clang__) */
>   
>     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..2924475 100644
> --- a/gdb/testsuite/gdb.base/vla-datatypes.exp
> +++ b/gdb/testsuite/gdb.base/vla-datatypes.exp
> @@ -15,6 +15,9 @@
>   
>   standard_testfile
>   
> +# Clang says it will never support variable length arrays in structures.
> +set is_clang [test_compiler_info clang*]
> +
>   if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
>       return -1
>   }
> @@ -41,14 +44,16 @@ gdb_test "print foo_vla" \
>            "\\\{\\\{a = 0\\\}, \\\{a = 2\\\}, \\\{a = 4\\\}, \\\{a = 6\\\}, \\\{a = 8\\\}\\\}"
>   gdb_test "print bar_vla" \
>            "\\\{\\\{x = 0, y = \\\{a = 0\\\}\\\}, \\\{x = 2, y = \\\{a = 2\\\}\\\}, \\\{x = 4, y = \\\{a = 4\\\}\\\}, \\\{x = 6, y = \\\{a = 6\\\}\\\}, \\\{x = 8, y = \\\{a = 8\\\}\\\}\\\}"
> -gdb_test "print vla_struct_object" \
> -    "\\\{something = 5, vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
> -gdb_test "print vla_union_object" \
> -    "\\\{vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
> -gdb_test "print vla_struct_typedef_struct_member_object" \
> -    "\\\{something = 10, vla_object = \\\{something = 15, vla_field = \\\{0, 3, 6, 9, 12\\\}\\\}\\\}"
> -gdb_test "print vla_struct_typedef_union_member_object" \
> -    "\\\{something = 6, vla_object = \\\{something = 6, vla_field = \\\{-1, 2, 5, 8, 11\\\}\\\}\\\}"
> +if {!$is_clang} {
> +    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 +70,10 @@ 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"
> +if {!$is_clang} {
> +    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 +89,12 @@ 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}"
> +if {!$is_clang} {
> +    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 +118,12 @@ 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"
> +if {!$is_clang} {
> +    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]
>