[PATCH] Fix reference of PU to CU for odr

[Tom de Vries <tdevries@suse.de>]

Hi,

When compiling dwz with the assert listed in the commit message for
"Call reorder_dups ASAP", and using test-case cc1.dwz-processed like so, we
run into:
...
$ dwz cc1.dwz-processed -o 1 -lnone --odr
dwz: dwz.c:12567: write_die: Assertion \
  `IMPLIES (cu->cu_kind == CU_PU, die_cu (refd)->cu_kind == CU_PU)' failed.
Aborted (core dumped)
...

The assert is related to this duplicate chain:
...
 28dd83f O b500801d 621b6872  pointer_type \
   (type: 28dd72f die_struct structure_type)
 2903769 O b500801d 621b6872  pointer_type \
   (type: 28dd72f die_struct structure_type)
...
which contains two DIEs that are both in the same CU:
...
 <0><28d281f>: Abbrev Number: 200 (DW_TAG_compile_unit)
 ...
 <1><28dd72f>: Abbrev Number: 35 (DW_TAG_structure_type)
    <28dd730>   DW_AT_name        : (indirect string, offset: 0x1b2ca6): die_struct
    <28dd734>   DW_AT_byte_size   : 80
    <28dd735>   DW_AT_decl_file   : 87
    <28dd736>   DW_AT_decl_line   : 3069
    <28dd738>   DW_AT_decl_column : 63
    <28dd739>   DW_AT_sibling     : <0x28dd83b>
 <1><28dd83f>: Abbrev Number: 9 (DW_TAG_pointer_type)
    <28dd840>   DW_AT_byte_size   : 8
    <28dd841>   DW_AT_type        : <0x28dd72f>
 ...
 <1><2903769>: Abbrev Number: 9 (DW_TAG_pointer_type)
    <290376a>   DW_AT_byte_size   : 8
    <290376b>   DW_AT_type        : <0x28dd72f>
 ...
 <0><2911617>: Abbrev Number: 177 (DW_TAG_compile_unit)
...

The dup chain is forced to a partial unit, but the die_struct DIE is not,
because it's not part of a duplicate chain, and it's not marked as a
singleton.  Fix this by marking the die_struct DIE as singleton.

Any comments?

Thanks,
- Tom

Fix reference of PU to CU for odr

2021-02-25  Tom de Vries  <tdevries@suse.de>

	PR dwz/27464
	* dwz.c (partition_dups): Call mark_singletons if
	cnt_ref_cus (die) == 1.

---
 dwz.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/dwz.c b/dwz.c
index 9172011..89cf8d1 100644
--- a/dwz.c
+++ b/dwz.c
@@ -8417,6 +8417,9 @@ partition_dups (void)
 	      if (s)
 		mark_singletons (die_cu (s), s, s, &ob2);
 	    }
+	  else if (cnt_ref_cus (die) == 1)
+	    mark_singletons (die_cu (die), die, die, &ob2);
+
 	  arr = (dw_die_ref *) obstack_base (&ob2);
 	}