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On openSUSE Leap 15.1 using rustc version 1.36.0 (using llvm 7), I get:
...
(gdb) PASS: gdb.rust/simple.exp: print e2.0
print k^M
$54 = simple::SpaceSaver::Thebox(40, 0x0)^M
(gdb) FAIL: gdb.rust/simple.exp: print k
...
while we're expecting:
...
gdb_test "print k" " = simple::SpaceSaver::Nothing"
...
When using a relatively recent version of Rust with a somewhat older version
of LLVM, the Rust compiler will emit a legacy encoding of enums (see also
quirk_rust_enum in dwarf2read.c).
So, the variable k:
...
<17><3d58>: Abbrev Number: 15 (DW_TAG_variable)
<3d59> DW_AT_location : 3 byte block: 91 b8 4 (DW_OP_fbreg: 568)
<3d5d> DW_AT_name : (indirect string, offset: 0xf9a): k
<3d61> DW_AT_alignment : 1
<3d62> DW_AT_decl_file : 1
<3d63> DW_AT_decl_line : 129
<3d64> DW_AT_type : <0x4232>
...
has type:
...
<2><4232>: Abbrev Number: 11 (DW_TAG_union_type)
<4233> DW_AT_name : (indirect string, offset: 0x3037): SpaceSaver
<4237> DW_AT_byte_size : 16
<4238> DW_AT_alignment : 8
<3><4239>: Abbrev Number: 9 (DW_TAG_member)
<423a> DW_AT_name : (indirect string, offset: 0x29f5): RUST$ENCODED$ENUM$0$Nothing
<423e> DW_AT_type : <0x4245>
<4242> DW_AT_alignment : 8
<4243> DW_AT_data_member_location: 0
...
The "RUST$ENCODED$ENUM$0$Nothing" means that field 0 is both a pointer and a
discriminant, and if the value is 0, then the enum is just a data-less variant
named "Nothing".
However, the corresponding type has two fields, where not field 0 but field 1
is a pointer, and field 0 is a byte:
...
<2><4245>: Abbrev Number: 8 (DW_TAG_structure_type)
<4246> DW_AT_name : (indirect string, offset: 0x2a11): Thebox
<424a> DW_AT_byte_size : 16
<424b> DW_AT_alignment : 8
<3><424c>: Abbrev Number: 9 (DW_TAG_member)
<424d> DW_AT_name : (indirect string, offset: 0x670): __0
<4251> DW_AT_type : <0x436b>
<4255> DW_AT_alignment : 1
<4256> DW_AT_data_member_location: 8
<3><4257>: Abbrev Number: 9 (DW_TAG_member)
<4258> DW_AT_name : (indirect string, offset: 0x1662): __1
<425c> DW_AT_type : <0x45da>
<4260> DW_AT_alignment : 8
<4261> DW_AT_data_member_location: 0
...
Mark this as xfail.
gdb/testsuite/ChangeLog:
2019-10-09 Tom de Vries <tdevries@suse.de>
PR testsuite/25048
* gdb.rust/simple.exp: Add xfails for incorrect DWARF.
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