From 77c2dba3e843694fae090e237ccdf1b8f65b94e6 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Thu, 3 Oct 2019 17:21:52 -0600 Subject: 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/dwarf2read.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'gdb/dwarf2read.c') diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index c0dd199..ee9df34 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; -- cgit v1.1