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

[Gary Benson <gbenson@redhat.com>]

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]
-- 
1.8.3.1