gdb: Fix pretty printer for nullable-opt enums with fat pointers.

Author: luqmana

src/etc/gdb_rust_pretty_printing.py

@@ -54,21 +54,27 @@ def rust_pretty_printer_lookup_function(val):
       return RustStructPrinter(val, false)
 
     if enum_member_count == 1:
-      if enum_members[0].name == None:
+      first_variant_name = enum_members[0].name
+      if first_variant_name == None:
         # This is a singleton enum
         return rust_pretty_printer_lookup_function(val[enum_members[0]])
       else:
-        assert enum_members[0].name.startswith("RUST$ENCODED$ENUM$")
+        assert first_variant_name.startswith("RUST$ENCODED$ENUM$")
         # This is a space-optimized enum
-        last_separator_index = enum_members[0].name.rfind("$")
+        last_separator_index = first_variant_name.rfind("$")
         second_last_separator_index = first_variant_name.rfind("$", 0, last_separator_index)
         disr_field_index = first_variant_name[second_last_separator_index + 1 :
                                               last_separator_index]
         disr_field_index = int(disr_field_index)
 
         sole_variant_val = val[enum_members[0]]
         disr_field = get_field_at_index(sole_variant_val, disr_field_index)
-        discriminant = int(sole_variant_val[disr_field])
+        discriminant = sole_variant_val[disr_field]
+
+        # If the discriminant field is a fat pointer we have to consider the
+        # first word as the true discriminant
+        if discriminant.type.code == gdb.TYPE_CODE_STRUCT:
+            discriminant = discriminant[get_field_at_index(discriminant, 0)]
 
         if discriminant == 0:
           null_variant_name = first_variant_name[last_separator_index + 1:]
@@ -173,7 +179,7 @@ def to_string(self):
 
 class IdentityPrinter:
   def __init__(self, string):
-    self.string
+    self.string = string
 
   def to_string(self):
     return self.string

src/test/debuginfo/gdb-pretty-struct-and-enums.rs

@@ -58,11 +58,17 @@
 // gdb-command: print none
 // gdb-check:$12 = None
 
+// gdb-command: print some_fat
+// gdb-check:$13 = Some = {"abc"}
+
+// gdb-command: print none_fat
+// gdb-check:$14 = None
+
 // gdb-command: print nested_variant1
-// gdb-check:$13 = NestedVariant1 = {NestedStruct = {regular_struct = RegularStruct = {the_first_field = 111, the_second_field = 112.5, the_third_field = true, the_fourth_field = "NestedStructString1"}, tuple_struct = TupleStruct = {113.5, 114}, empty_struct = EmptyStruct, c_style_enum = CStyleEnumVar2, mixed_enum = MixedEnumTupleVar = {115, 116, false}}}
+// gdb-check:$15 = NestedVariant1 = {NestedStruct = {regular_struct = RegularStruct = {the_first_field = 111, the_second_field = 112.5, the_third_field = true, the_fourth_field = "NestedStructString1"}, tuple_struct = TupleStruct = {113.5, 114}, empty_struct = EmptyStruct, c_style_enum = CStyleEnumVar2, mixed_enum = MixedEnumTupleVar = {115, 116, false}}}
 
 // gdb-command: print nested_variant2
-// gdb-check:$14 = NestedVariant2 = {abc = NestedStruct = {regular_struct = RegularStruct = {the_first_field = 117, the_second_field = 118.5, the_third_field = false, the_fourth_field = "NestedStructString10"}, tuple_struct = TupleStruct = {119.5, 120}, empty_struct = EmptyStruct, c_style_enum = CStyleEnumVar3, mixed_enum = MixedEnumStructVar = {field1 = 121.5, field2 = -122}}}
+// gdb-check:$16 = NestedVariant2 = {abc = NestedStruct = {regular_struct = RegularStruct = {the_first_field = 117, the_second_field = 118.5, the_third_field = false, the_fourth_field = "NestedStructString10"}, tuple_struct = TupleStruct = {119.5, 120}, empty_struct = EmptyStruct, c_style_enum = CStyleEnumVar3, mixed_enum = MixedEnumStructVar = {field1 = 121.5, field2 = -122}}}
 
 use self::CStyleEnum::{CStyleEnumVar1, CStyleEnumVar2, CStyleEnumVar3};
 use self::MixedEnum::{MixedEnumCStyleVar, MixedEnumTupleVar, MixedEnumStructVar};
@@ -129,6 +135,8 @@ fn main() {
 
     let some = Some(110u);
     let none: Option<int> = None;
+    let some_fat = Some("abc");
+    let none_fat: Option<&'static str> = None;
 
     let nested_variant1 = NestedVariant1(
         NestedStruct {