Set TYPE_LENGTH on a variant part

gdb represents a DW_TAG_variant_part as a union.  While normally DWARF
would not set the size of a DW_TAG_variant_part, gdb's representation
requires the TYPE_LENGTH to be set.

This patch arranges to set the TYPE_LENGTH of a variant part if it has
not already been set.

This fixes some Rust regressions when testing against a version of
rustc that emits DW_TAG_variant_part.

gdb/ChangeLog
2018-08-31  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (dwarf2_add_field): Set the TYPE_LENGTH of the
	variant part type.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bd866d9..83348d5 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-31  Tom Tromey  <tom@tromey.com>
+
+       * dwarf2read.c (dwarf2_add_field): Set the TYPE_LENGTH of the
+       variant part type.
+
 2018-08-31  Pedro Alves  <palves@redhat.com>
 
        * gdbarch.h: Regenerate.

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 8834d08..d66dfea 100644 (file)
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -15169,6 +15169,18 @@ dwarf2_add_field (struct field_info *fip, struct die_info *die,
       fp->type = get_die_type (die, cu);
       fp->artificial = 1;
       fp->name = "<<variant>>";
+
+      /* Normally a DW_TAG_variant_part won't have a size, but our
+        representation requires one, so set it to the maximum of the
+        child sizes.  */
+      if (TYPE_LENGTH (fp->type) == 0)
+       {
+         unsigned max = 0;
+         for (int i = 0; i < TYPE_NFIELDS (fp->type); ++i)
+           if (TYPE_LENGTH (TYPE_FIELD_TYPE (fp->type, i)) > max)
+             max = TYPE_LENGTH (TYPE_FIELD_TYPE (fp->type, i));
+         TYPE_LENGTH (fp->type) = max;
+       }
     }
   else
     gdb_assert_not_reached ("missing case in dwarf2_add_field");