Bug 27464

Summary: CU referenced from PU (--odr-mode=link case) (bis)
Product: dwz Reporter: Tom de Vries <vries>
Component: defaultAssignee: Nobody <nobody>
Status: RESOLVED FIXED    
Severity: normal CC: dwz
Priority: P2    
Version: unspecified   
Target Milestone: ---   
Host: Target:
Build: Last reconfirmed:
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Description Tom de Vries 2021-02-24 17:37:21 UTC 
Using the same assert as in PR25424, and using the tentative patch series, we run into:
...
$ dwz cc1.dwz-processed -o 1 -lnone --odr 
dwz: /home/vries/dwz/dwz.git/dwz.c:12601: write_die: Assertion `IMPLIES (cu->cu_kind == CU_PU, die_cu (refd)->cu_kind == CU_PU)' failed.
Aborted (core dumped)
...

This is related to the 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 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.
Comment 1 Tom de Vries 2021-02-24 17:39:04 UTC 
Tentative fix:
...
diff --git a/dwz.c b/dwz.c
index 7bd18e3..89a231f 100644
--- a/dwz.c
+++ b/dwz.c
@@ -8445,6 +8445,9 @@ 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);
        }
 
...