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From: "dmitry.neverov at jetbrains dot com"
 <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug symtab/31295] New: Slow symbol lookup due to missing
 DW_AT_const_value attribute
Date: Thu, 25 Jan 2024 16:24:29 +0000
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X-Bugzilla-Product: gdb
X-Bugzilla-Component: symtab
X-Bugzilla-Version: 14.1
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: dmitry.neverov at jetbrains dot com
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X-Bugzilla-Priority: P2
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31295

            Bug ID: 31295
           Summary: Slow symbol lookup due to missing DW_AT_const_value
                    attribute
           Product: gdb
           Version: 14.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: symtab
          Assignee: unassigned at sourceware dot org
          Reporter: dmitry.neverov at jetbrains dot com
  Target Milestone: ---

DWARF for npos in the following program=20

class wxString
{
public:
  static const size_t npos;
};

const size_t wxString::npos =3D (size_t) -1;

int main() {
  return 0;
}

doesn't have the DW_AT_const_value attribute:

< 2><0x000005cd>      DW_TAG_variable
                        DW_AT_name                  npos
                        DW_AT_decl_file             0x00000001
/path/to/main.cpp
                        DW_AT_decl_line             0x00000006
                        DW_AT_decl_column           0x00000017
                        DW_AT_linkage_name          _ZN8wxString4nposE
                        DW_AT_type                  <0x0000003a>
                        DW_AT_external              yes(1)
                        DW_AT_accessibility         DW_ACCESS_public
                        DW_AT_declaration           yes(1)

If the wxString is used in many CUs, listing fields of the
wxString variable will lookup the wxString::npos name, which
triggers CU expansion. But the dwarf2_add_field (read.c:11699)
doesn't create a symbol if the DW_AT_const_value is missing, so
expansion is done, but the symbol is not found. As a result all
CUs with the symbol are expanded and symbol lookup takes around a
minute on a 500Mb .so file.

--=20
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