[PATCH] rust/25535 Apply embedded offset to enum variant calculation

["Doug Evans via gdb-patches" <gdb-patches@sourceware.org>]

Hopefully straightforward (and I didn't miss anything ...).

gdb/ChangeLog
        PR rust/25535
        * rust-lang.c (rust_print_enum): Apply embedded_offset to
        rust_enum_variant calculation.

gdb/testsuite/ChangeLog
        PR rust/25535
        * gdb.rust/simple.exp: Add test.
        * gdb.rust/simple.rs: Add test.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 91d7cec98af..1d8af99d8d6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2020-02-11  Doug Evans  <dje@google.com>
+
+	PR rust/25535
+	* rust-lang.c (rust_print_enum): Apply embedded_offset to
+	rust_enum_variant calculation.
+
 2020-02-11  Christian Biesinger  <cbiesinger@google.com>
 
 	* cris-tdep.c (cris_supply_gregset): Change signature to match
diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 9123bf2146d..18dc6a56471 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -481,7 +481,8 @@ rust_print_enum (struct type *type, int embedded_offset,
     }
 
   const gdb_byte *valaddr = value_contents_for_printing (val);
-  struct field *variant_field = rust_enum_variant (type, valaddr);
+  struct field *variant_field = rust_enum_variant (type,
+						   valaddr + embedded_offset);
   embedded_offset += FIELD_BITPOS (*variant_field) / 8;
   struct type *variant_type = FIELD_TYPE (*variant_field);
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 06826746d5f..a613c1e6565 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-02-11  Doug Evans  <dje@google.com>
+
+	PR rust/25535
+	* gdb.rust/simple.exp: Add test.
+	* gdb.rust/simple.rs: Add test.
+
 2020-02-11  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	PR tui/25126
diff --git a/gdb/testsuite/gdb.rust/simple.exp b/gdb/testsuite/gdb.rust/simple.exp
index aa64e6b08f1..b4fcf274261 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -357,6 +357,8 @@ gdb_test_sequence "ptype/o SimpleLayout" "" {
 
 gdb_test "print u2" " = simple::Union2 {name: \\\[1\\\]}"
 
+gdb_test "print nonzero_offset" " = simple::EnumWithNonzeroOffset {a: core::option::Option<u8>::Some\\(1\\), b: core::option::Option<u8>::None}"
+
 # PR rust/23626 - this used to crash.  Note that the results are
 # fairly lax because most existing versions of Rust (those before the
 # DW_TAG_variant patches) do not emit what gdb wants here; and there
diff --git a/gdb/testsuite/gdb.rust/simple.rs b/gdb/testsuite/gdb.rust/simple.rs
index 1280e04449b..36448ec45c6 100644
--- a/gdb/testsuite/gdb.rust/simple.rs
+++ b/gdb/testsuite/gdb.rust/simple.rs
@@ -104,6 +104,12 @@ struct SimpleLayout {
 
 enum EmptyEnum {}
 
+#[derive(Debug)]
+struct EnumWithNonzeroOffset {
+    a: Option<u8>,
+    b: Option<u8>,
+}
+
 fn main () {
     let a = ();
     let b : [i32; 0] = [];
@@ -186,6 +192,8 @@ fn main () {
 
     let u2 = Union2 { name: [1] };
 
+    let nonzero_offset = EnumWithNonzeroOffset { a: Some(1), b: None };
+
     println!("{}, {}", x.0, x.1);        // set breakpoint here
     println!("{}", diff2(92, 45));
     empty();