[PATCH] Fix handling of discriminantless univariant enums in Rust

Manish Goregaokar
2016-10-27T23:52:15Z

Fixes an issue caught by TimNN in https://github.com/rust-lang/rust/pull/37410

From: Manish Goregaokar <manish@mozilla.com>
Date: Thu, 27 Oct 2016 16:46:34 -0700
Subject: Fix handling of discriminantless univariant enums in Rust

2016-10-27 Manish Goregaokar <manish@mozilla.com>

gdb/ChangeLog:
* rust-lang.c (rust_get_disr_info): Treat univariant enums
without discriminants as encoded enums with a real field

gdb/testsuite/ChangeLog:
* simple.rs: Add test for univariant enums without discriminants
* simple.exp: Add test expectations
---
gdb/rust-lang.c | 13 ++++++++++++-
gdb/testsuite/gdb.rust/simple.exp | 2 ++
gdb/testsuite/gdb.rust/simple.rs | 6 ++++++
3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 82cd3f9..9d13353 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -194,7 +194,18 @@ rust_get_disr_info (struct type *type, const
gdb_byte *valaddr,
has changed its debuginfo format. */
error (_("Could not find enum discriminant field"));
}
-
+ else if (TYPE_NFIELDS (type) == 1) {
+ /* Sometimes univariant enums are encoded without a
+ discriminant. In that case, treating it as an encoded enum
+ with the first field being the actual type works. */
+ const char* field_name = TYPE_NAME (TYPE_FIELD_TYPE (type, 0));
+ ret.name = concat (TYPE_NAME (type), "::",
+ rust_last_path_segment (field_name),
+ (char *) NULL);
+ ret.field_no = RUST_ENCODED_ENUM_REAL;
+ ret.is_encoded = 1;
+ return ret;
+ }
if (strcmp (TYPE_FIELD_NAME (disr_type, 0), "RUST$ENUM$DISR") != 0)
error (_("Rust debug format has changed"));

diff --git a/gdb/testsuite/gdb.rust/simple.exp
b/gdb/testsuite/gdb.rust/simple.exp
index 5e00b03..dbfc88a 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -103,6 +103,8 @@ gdb_test_sequence "ptype z" "" {
}
gdb_test "print z.1" " = 8"

+gdb_test "print univariant" " = simple::Univariant::Foo{a: 1}"
+
gdb_test_sequence "ptype simple::ByeBob" "" {
" = struct simple::ByeBob \\("
" i32,"
diff --git a/gdb/testsuite/gdb.rust/simple.rs b/gdb/testsuite/gdb.rust/simple.rs
index eeff3d7..b2e29ae 100644
--- a/gdb/testsuite/gdb.rust/simple.rs
+++ b/gdb/testsuite/gdb.rust/simple.rs
@@ -63,6 +63,10 @@ enum SpaceSaver {
Nothing,
}

+enum Univariant {
+ Foo {a: u8}
+}
+
fn main () {
let a = ();
let b : [i32; 0] = [];
@@ -93,6 +97,8 @@ fn main () {
let y = HiBob {field1: 7, field2: 8};
let z = ByeBob(7, 8);

+ let univariant = Univariant::Foo {a : 1};
+
let slice = &w[2..3];
let fromslice = slice[0];
let slice2 = &slice[0..1];
--
2.10.1