[FYI] Avoid crash on single-field union in Rust
Commit Message
PR rust/24976 points out a crash in gdb when a single-field union is
used in Rust.
The immediate problem was a NULL pointer dereference in
quirk_rust_enum. However, that code is also erroneously treating a
single-field union as if it were a univariant enum. Looking at the
output of an older Rust compiler, it turns out that univariant enums
are distinguished by having a single *anonymous* field. This patch
changes quirk_rust_enum to limit its fixup to this case.
Tested with a new-enough version of the Rust compiler to cause the
crash; plus by using an older executable that uses the old univariant
encoding.
gdb/ChangeLog
2019-10-03 Tom Tromey <tom@tromey.com>
PR rust/24976:
* dwarf2read.c (quirk_rust_enum): Handle single-element unions.
gdb/testsuite/ChangeLog
2019-10-03 Tom Tromey <tom@tromey.com>
PR rust/24976:
* gdb.rust/simple.rs (Union2): New type.
(main): Use Union2.
* gdb.rust/simple.exp: Add test.
---
gdb/ChangeLog | 5 +++++
gdb/dwarf2read.c | 6 +++---
gdb/testsuite/ChangeLog | 7 +++++++
gdb/testsuite/gdb.rust/simple.exp | 2 ++
gdb/testsuite/gdb.rust/simple.rs | 6 ++++++
5 files changed, 23 insertions(+), 3 deletions(-)
@@ -10076,10 +10076,10 @@ quirk_rust_enum (struct type *type, struct objfile *objfile)
SET_FIELD_BITPOS (TYPE_FIELD (type, 0), 0);
TYPE_FIELD_NAME (type, 0) = "<<variants>>";
}
- else if (TYPE_NFIELDS (type) == 1)
+ /* A union with a single anonymous field is probably an old-style
+ univariant enum. */
+ else if (TYPE_NFIELDS (type) == 1 && streq (TYPE_FIELD_NAME (type, 0), ""))
{
- /* We assume that a union with a single field is a univariant
- enum. */
/* Smash this type to be a structure type. We have to do this
because the type has already been recorded. */
TYPE_CODE (type) = TYPE_CODE_STRUCT;
@@ -309,6 +309,8 @@ gdb_test_sequence "ptype/o SimpleLayout" "" {
" }"
}
+gdb_test "print u2" " = simple::Union2 {name: \\\[1\\\]}"
+
# 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
@@ -85,6 +85,10 @@ union Union {
f2: u8,
}
+pub union Union2 {
+ pub name: [u8; 1],
+}
+
struct StringAtOffset {
pub field1: &'static str,
pub field2: i32,
@@ -180,6 +184,8 @@ fn main () {
let empty_enum_value: EmptyEnum;
+ let u2 = Union2 { name: [1] };
+
println!("{}, {}", x.0, x.1); // set breakpoint here
println!("{}", diff2(92, 45));
empty();