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

Manish Goregaokar
2016-10-31T03:47:37Z

Yeah, have gone through the document, but I still miss things :)

From 7a2296aabb423ade3bc6bb675cf97123ba939eb4 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manish@mozilla.com>
Date: Thu, 27 Oct 2016 16:46:34 -0700
Subject: [PATCH 1/3] Fix handling of discriminantless univariant enums in
Rust; fix bug with encoded enums

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

gdb/testsuite/ChangeLog:
* simple.rs: Add test for univariant enums without discriminants
and for encoded struct-like enums
* simple.exp: Add test expectations
---
gdb/rust-lang.c | 16 +++++++++++++++-
gdb/testsuite/gdb.rust/simple.exp | 12 ++++++++++++
gdb/testsuite/gdb.rust/simple.rs | 30 ++++++++++++++++++++++++++++++
3 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index 82cd3f9..774eed9 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -194,6 +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));
+ const char *last = rust_last_path_segment (field_name);
+ ret.name = concat (TYPE_NAME (type), "::", last, (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"));
@@ -1725,7 +1737,9 @@ 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 5e00b03..8e84daa 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -103,6 +103,11 @@ gdb_test_sequence "ptype z" "" {
}
gdb_test "print z.1" " = 8"

+gdb_test "print univariant" " = simple::Univariant::Foo{a: 1}"
+gdb_test "print univariant.a" " = 1"
+gdb_test "print univariant_anon" " = simple::UnivariantAnon::Foo\\(1\\)"
+gdb_test "print univariant_anon.0" " = 1"
+
gdb_test_sequence "ptype simple::ByeBob" "" {
" = struct simple::ByeBob \\("
" i32,"
@@ -220,3 +225,10 @@ 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\\}"
diff --git a/gdb/testsuite/gdb.rust/simple.rs b/gdb/testsuite/gdb.rust/simple.rs
index eeff3d7..670f54e 100644
--- a/gdb/testsuite/gdb.rust/simple.rs
+++ b/gdb/testsuite/gdb.rust/simple.rs
@@ -63,6 +63,23 @@ enum SpaceSaver {
Nothing,
}

+enum Univariant {
+ Foo {a: u8}
+}
+enum UnivariantAnon {
+ Foo(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] = [];
@@ -93,6 +110,9 @@ fn main () {
let y = HiBob {field1: 7, field2: 8};
let z = ByeBob(7, 8);

+ let univariant = Univariant::Foo {a : 1};
+ let univariant_anon = UnivariantAnon::Foo(1);
+
let slice = &w[2..3];
let fromslice = slice[0];
let slice2 = &slice[0..1];
@@ -117,6 +137,16 @@ 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 Sun, Oct 30, 2016 at 8:29 PM, Tom Tromey <tom@tromey.com> wrote:
>>>>>> "Manish" == Manish Goregaokar <manish@mozilla.com> writes:
>
> Manish> Updated. Not sure what the style issues are, could you point them out?
>
> Sure. There's also the GNU coding standards document, plus some docs on
> the gdb wiki somewhere.
>
> Manish> }
> Manish> + else if (TYPE_NFIELDS (type) == 1) {
>
> Brace placement. Should line up with that "}" just above.
>
> Manish> + /* Sometimes univariant enums are encoded without a
> Manish> + discriminant. In that case, treating it as an encoded enum
> Manish> + with the first field being the actual type works. */
>
> Subsequent text in a multi-line comment should line up under the
> "Sometimes".
>
> Period followed by two spaces ends a sentence, so one more space before
> "In".
>
> Manish> + const char* field_name = TYPE_NAME (TYPE_FIELD_TYPE (type, 0));
> Manish> + const char* last = rust_last_path_segment (field_name);
>
> "char *"
>
> Manish> + ret.name = concat (TYPE_NAME (type), "::", last, (char *) NULL);
> Manish> + ret.field_no = RUST_ENCODED_ENUM_REAL;
> Manish> + ret.is_encoded = 1;
> Manish> + return ret;
> Manish> + }
>
> This brace and the whole block will be indented a bit more due to the
> brace placement issue.
>
> thanks,
> Tom