From 77c2dba3e843694fae090e237ccdf1b8f65b94e6 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Thu, 3 Oct 2019 17:21:52 -0600 Subject: [PATCH] Avoid crash on single-field union in Rust 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 PR rust/24976: * dwarf2read.c (quirk_rust_enum): Handle single-element unions. gdb/testsuite/ChangeLog 2019-10-03 Tom Tromey 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(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 446c45501d..4eeed4931e 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2019-10-03 Tom Tromey + + PR rust/24976: + * dwarf2read.c (quirk_rust_enum): Handle single-element unions. + 2019-10-03 Andrew Burgess * f-lang.c (f_language_defn): Use cp_get_symbol_name_matcher and diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index c0dd199a79..ee9df34ed2 100644 --- a/gdb/dwarf2read.c +++ b/gdb/dwarf2read.c @@ -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) = "<>"; } - 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; diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index fd7614403c..f42a0a3c83 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,10 @@ +2019-10-03 Tom Tromey + + PR rust/24976: + * gdb.rust/simple.rs (Union2): New type. + (main): Use Union2. + * gdb.rust/simple.exp: Add test. + 2019-10-03 Andrew Burgess * gdb.fortran/nested-funcs-2.exp: Run tests with and without the diff --git a/gdb/testsuite/gdb.rust/simple.exp b/gdb/testsuite/gdb.rust/simple.exp index 7211bd29be..dcbfb90920 100644 --- a/gdb/testsuite/gdb.rust/simple.exp +++ b/gdb/testsuite/gdb.rust/simple.exp @@ -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 diff --git a/gdb/testsuite/gdb.rust/simple.rs b/gdb/testsuite/gdb.rust/simple.rs index e6e0efd3b1..65b57f42df 100644 --- a/gdb/testsuite/gdb.rust/simple.rs +++ b/gdb/testsuite/gdb.rust/simple.rs @@ -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(); -- 2.34.1