dwarf_loader: Hash DW_TAG_enumerator entries

As they are referenced by DW_TAG_imported_declaration, as we can see
from these warnings:

  ⬢[acme@toolbox [email protected]]$ pdwtags popup.cpp.o > /dev/null
  die__process_class: tag not supported 0x2f (template_type_parameter)!
  die__process_class: tag not supported 0x30 (template_value_parameter)!
  die__process_class: tag not supported 0x4107 (GNU_template_parameter_pack)!
  die__process_function: tag not supported 0x4108 (GNU_formal_parameter_pack)!
  tag__recode_dwarf_type: couldn't find 0x5706e type for 0xedb9 (imported_declaration)!
  tag__recode_dwarf_type: couldn't find 0x57074 type for 0xedc1 (imported_declaration)!
  tag__recode_dwarf_type: couldn't find 0x5707a type for 0xedc9 (imported_declaration)!
  namespace__recode_dwarf_types: couldn't find 0x5706e type for 0xedb9 (imported_declaration)!
  namespace__recode_dwarf_types: couldn't find 0x57074 type for 0xedc1 (imported_declaration)!
  namespace__recode_dwarf_types: couldn't find 0x5707a type for 0xedc9 (imported_declaration)!
  ⬢[acme@toolbox [email protected]]$

Looking at the DWARF info for one of those types not found:

  ⬢[acme@toolbox [email protected]]$ readelf -wi popup.cpp.o | grep -w edb9 -A5
   <2><edb9>: Abbrev Number: 14 (DW_TAG_imported_declaration)
      <edba>   DW_AT_decl_file   : 64
      <edbb>   DW_AT_decl_line   : 100
      <edbc>   DW_AT_decl_column : 20
      <edbd>   DW_AT_import      : <0x5706e>	[Abbrev Number: 51 (DW_TAG_enumerator)]
   <2><edc1>: Abbrev Number: 14 (DW_TAG_imported_declaration)
  ⬢[acme@toolbox [email protected]]$

And then:

  ⬢[acme@toolbox [email protected]]$ readelf -wi popup.cpp.o | grep -w 5706e -A3
   <3><5706e>: Abbrev Number: 51 (DW_TAG_enumerator)
      <5706f>   DW_AT_name        : (indirect string, offset: 0xaec05): _S_single
      <57073>   DW_AT_const_value : 0
   <3><57074>: Abbrev Number: 51 (DW_TAG_enumerator)
  ⬢[acme@toolbox [email protected]]$

So we need to hash those DW_TAG_enumerator and not just the
DW_TAG_enumerator_type containing them.

This way tag__recode_dwarf_type() and namespace__recode_dwarf_types()
will find them when looking them up using dwarf_cu__find_type_by_ref().

This was found first on the stratagus codebase (C++) at
https://github.com/Wargus/stratagus.git.

This didn't generate any difference in output from pahole, not
influenced BTF generation as tested using tests/reproducible_build.sh.

Reported-by: Matthias Schwarzott <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: acmel

dwarf_loader.c

@@ -1776,6 +1776,7 @@ static struct tag *die__create_new_enumeration(Dwarf_Die *die, struct cu *cu, st
 			goto out_delete;
 
 		enumeration__add(enumeration, enumerator);
+		cu__hash(cu, &enumerator->tag);
 	} while (dwarf_siblingof(die, die) == 0);
 out:
 	return &enumeration->namespace.tag;