Re: [PATCH] Fix handling of discriminantless univariant enums in Rust

Manish Goregaokar
2016-10-28T19:57:30Z

Fixed another enum issue, reported in the same PR:

(I'm not sure if this is the correct fix)

From: Manish Goregaokar <manish@mozilla.com>
Date: Thu, 27 Oct 2016 16:46:34 -0700
Subject: Handle field access on encoded struct-like enums

2016-10-28 Manish Goregaokar <manish@mozilla.com>

gdb/ChangeLog:
* rust-lang.c (rust_evaluate_subexp): Handle field access
on encoded struct-like enums

gdb/testsuite/ChangeLog:
* simple.rs: Add test for encoded struct-like enums
* simple.exp: Add test expectations
---
gdb/rust-lang.c | 4 +++-
gdb/testsuite/gdb.rust/simple.exp | 6 ++++++
gdb/testsuite/gdb.rust/simple.rs | 20 ++++++++++++++++++++
3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 9d13353..9569584 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -1736,7 +1736,9 @@ tuple structs, and tuple-like enum variants"));
variant_type = TYPE_FIELD_TYPE (type, disr.field_no);

if (variant_type == NULL
- || rust_tuple_variant_type_p (variant_type))
+ || (disr.is_encoded
+ ? rust_tuple_struct_type_p (variant_type)
+ : rust_tuple_variant_type_p (variant_type)))
error(_("Attempting to access named field %s of tuple variant %s, \
which has only anonymous fields"),
field_name, disr.name);
diff --git a/gdb/testsuite/gdb.rust/simple.exp
b/gdb/testsuite/gdb.rust/simple.exp
index dbfc88a..075bff7 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -222,3 +222,9 @@ gdb_test "print (1,)" "Tuple expressions not supported yet"
gdb_test "print (1)" " = 1"

gdb_test "print 23..97.0" "Range expression with different types"
+
+gdb_test "print (*parametrized.next.val)" \
+ " = simple::ParametrizedStruct<i32> {next:
simple::ParametrizedEnum<Box<simple::ParametrizedStruct<i32>>>::Empty,
value: 1}"
+gdb_test "print parametrized.next.val" " =
\\(simple::ParametrizedStruct<i32> \\*\\) $hex"
+gdb_test "print parametrized" \
+ " = simple::ParametrizedStruct<i32> \\{next:
simple::ParametrizedEnum<Box<simple::ParametrizedStruct<i32>>>::Val\\{val:
$hex\\}, value: 0\\}"
\ No newline at end of file
diff --git a/gdb/testsuite/gdb.rust/simple.rs b/gdb/testsuite/gdb.rust/simple.rs
index b2e29ae..e756296 100644
--- a/gdb/testsuite/gdb.rust/simple.rs
+++ b/gdb/testsuite/gdb.rust/simple.rs
@@ -67,6 +67,16 @@ enum Univariant {
Foo {a: u8}
}

+enum ParametrizedEnum<T> {
+ Val { val: T },
+ Empty,
+}
+
+struct ParametrizedStruct<T> {
+ next: ParametrizedEnum<Box<ParametrizedStruct<T>>>,
+ value: T
+}
+
fn main () {
let a = ();
let b : [i32; 0] = [];
@@ -123,6 +133,16 @@ fn main () {
let custom_some = NonZeroOptimized::Value("hi".into());
let custom_none = NonZeroOptimized::Empty;

+ let parametrized = ParametrizedStruct {
+ next: ParametrizedEnum::Val {
+ val: Box::new(ParametrizedStruct {
+ next: ParametrizedEnum::Empty,
+ value: 1,
+ })
+ },
+ value: 0,
+ };
+
println!("{}, {}", x.0, x.1); // set breakpoint here
println!("{}", diff2(92, 45));
empty();
--
2.10.1

-Manish

On Thu, Oct 27, 2016 at 4:51 PM, Manish Goregaokar <manish@mozilla.com> wrote:
> 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