[debug] DWARF: add DW_AT_count to zero-length arrays

2018-09-13  Omar Sandoval  <osandov@osandov.com>
	    Tom de Vries  <tdevries@suse.de>

	PR debug/86985
	* dwarf2out.c (is_c): New function.
	(add_subscript_info): Add DW_AT_count of 0 for C zero-length arrays.

	* gcc.dg/guality/zero-length-array.c: New test.

Co-Authored-By: Tom de Vries <tdevries@suse.de>

From-SVN: r264267

4 files changed, 58 insertions, 2 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 99b894b..e62f461 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-13  Omar Sandoval  <osandov@osandov.com>
+	    Tom de Vries  <tdevries@suse.de>
+
+	PR debug/86985
+	* dwarf2out.c (is_c): New function.
+	(add_subscript_info): Add DW_AT_count of 0 for C zero-length arrays.
+
 2018-09-13  Sam Tebbs  <sam.tebbs@arm.com>
 
 	PR target/85628
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 9e9da30..48c5037 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -3679,6 +3679,7 @@ static const char *get_AT_string (dw_die_ref, enum dwarf_attribute);
 static int get_AT_flag (dw_die_ref, enum dwarf_attribute);
 static unsigned get_AT_unsigned (dw_die_ref, enum dwarf_attribute);
 static inline dw_die_ref get_AT_ref (dw_die_ref, enum dwarf_attribute);
+static bool is_c (void);
 static bool is_cxx (void);
 static bool is_cxx (const_tree);
 static bool is_fortran (void);
@@ -5443,6 +5444,19 @@ get_AT_file (dw_die_ref die, enum dwarf_attribute attr_kind)
   return a ? AT_file (a) : NULL;
 }
 
+/* Return TRUE if the language is C.  */
+
+static inline bool
+is_c (void)
+{
+  unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
+
+  return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_C99
+	  || lang == DW_LANG_C11 || lang == DW_LANG_ObjC);
+
+
+}
+
 /* Return TRUE if the language is C++.  */
 
 static inline bool
@@ -21000,8 +21014,16 @@ add_subscript_info (dw_die_ref type_die, tree type, bool collapse_p)
 
 	  if (!get_AT (subrange_die, DW_AT_lower_bound))
 	    add_bound_info (subrange_die, DW_AT_lower_bound, lower, NULL);
-	  if (upper && !get_AT (subrange_die, DW_AT_upper_bound))
-	    add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
+	  if (!get_AT (subrange_die, DW_AT_upper_bound)
+	      && !get_AT (subrange_die, DW_AT_count))
+	    {
+	      if (upper)
+		add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
+	      else if ((is_c () || is_cxx ()) && COMPLETE_TYPE_P (type))
+		/* Zero-length array.  */
+		add_bound_info (subrange_die, DW_AT_count,
+				build_int_cst (TREE_TYPE (lower), 0), NULL);
+	    }
 	}
 
       /* Otherwise we have an array type with an unspecified length.  The
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 08915bb..be1e8b5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2018-09-13  Omar Sandoval  <osandov@osandov.com>
+	    Tom de Vries  <tdevries@suse.de>
+
+	PR debug/86985
+	* gcc.dg/guality/zero-length-array.c: New test.
+
 2018-09-13  Sam Tebbs  <sam.tebbs@arm.com>
 
 	PR target/85628
diff --git a/gcc/testsuite/gcc.dg/guality/zero-length-array.c b/gcc/testsuite/gcc.dg/guality/zero-length-array.c
new file mode 100644
index 0000000..33f34d9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/guality/zero-length-array.c
@@ -0,0 +1,21 @@
+/* PR debug/86985 */
+/* { dg-do run } */
+/* { dg-options "-g" } */
+
+struct {
+  int foo;
+  int bar[0];
+} zla; /* Zero length array.  */
+
+struct {
+  int foo;
+  int bar[];
+} fam; /* Flexible array member.  */
+
+int
+main ()
+{
+  /* { dg-final { gdb-test . "type:zla" "struct { int foo; int bar[0]; }" } } */
+  /* { dg-final { gdb-test . "type:fam" "struct { int foo; int bar[]; }" } } */
+  return 0;
+}