diff mbox series

[09/13] Use correct sign for variant part discriminants

Message ID 20250320-attribute-madness-v1-9-79d42789f881@adacore.com
State New
Headers
Series More work on DW_FORM_* and sign handling |

Checks

Context Check Description
linaro-tcwg-bot/tcwg_gdb_build--master-aarch64 fail Patch failed to apply
linaro-tcwg-bot/tcwg_gdb_build--master-arm fail Patch failed to apply

Commit Message

Tom Tromey March 20, 2025, 7:27 p.m. UTC 
  The discriminant value for a variant part may be signed or unsigned,
depending on the type of the variant.  This patch changes the DWARF
reader to delay interpretation of the relevant attribute until the
signed-ness is known.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32680
---
 gdb/dwarf2/read.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)
diff mbox series

Patch

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index e6ab3c8b596f3fc1c627efd6e9e7146fb40a3575..6bfdac82e08f32f9d9172ee8f16a27a0a1f0f6f9 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -622,15 +622,21 @@  struct variant_field
   /* A variant can contain other variant parts.  */
   std::vector<variant_part_builder> variant_parts;
 
-  /* If we see a DW_TAG_variant, then this will be set if this is the
-     default branch.  */
-  bool default_branch = false;
   /* If we see a DW_AT_discr_value, then this will be the discriminant
-     value.  */
-  ULONGEST discriminant_value = 0;
+     value.  Just the attribute is stored here, because we have to
+     defer deciding whether the value is signed or unsigned until the
+     end.  */
+  const attribute *discriminant_attr = nullptr;
   /* If we see a DW_AT_discr_list, then this is a pointer to the list
      data.  */
   struct dwarf_block *discr_list_data = nullptr;
+
+  /* If both DW_AT_discr_value and DW_AT_discr_list are absent, then
+     this is the default branch.  */
+  bool is_default () const
+  {
+    return discriminant_attr == nullptr && discr_list_data == nullptr;
+  }
 };
 
 /* This represents a DW_TAG_variant_part.  */
@@ -10356,13 +10362,19 @@  convert_variant_range (struct obstack *obstack, const variant_field &variant,
 {
   std::vector<discriminant_range> ranges;
 
-  if (variant.default_branch)
+  if (variant.is_default ())
     return {};
 
   if (variant.discr_list_data == nullptr)
     {
-      discriminant_range r
-	= {variant.discriminant_value, variant.discriminant_value};
+      ULONGEST value;
+
+      if (is_unsigned)
+	value = variant.discriminant_attr->unsigned_constant ().value_or (0);
+      else
+	value = variant.discriminant_attr->signed_constant ().value_or (0);
+
+      discriminant_range r = { value, value };
       ranges.push_back (r);
     }
   else
@@ -11323,12 +11335,14 @@  handle_variant (struct die_info *die, struct type *type,
     {
       discr = dwarf2_attr (die, DW_AT_discr_list, cu);
       if (discr == nullptr || discr->as_block ()->size == 0)
-	variant.default_branch = true;
+	{
+	  /* Nothing to do here -- default branch.  */
+	}
       else
 	variant.discr_list_data = discr->as_block ();
     }
   else
-    variant.discriminant_value = discr->constant_value (0);
+    variant.discriminant_attr = discr;
 
   for (die_info *variant_child = die->child;
        variant_child != NULL;