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      1 /* Low-level DWARF 2 reading code
      2 
      3    Copyright (C) 1994-2024 Free Software Foundation, Inc.
      4 
      5    Adapted by Gary Funck (gary (at) intrepid.com), Intrepid Technology,
      6    Inc.  with support from Florida State University (under contract
      7    with the Ada Joint Program Office), and Silicon Graphics, Inc.
      8    Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
      9    based on Fred Fish's (Cygnus Support) implementation of DWARF 1
     10    support.
     11 
     12    This file is part of GDB.
     13 
     14    This program is free software; you can redistribute it and/or modify
     15    it under the terms of the GNU General Public License as published by
     16    the Free Software Foundation; either version 3 of the License, or
     17    (at your option) any later version.
     18 
     19    This program is distributed in the hope that it will be useful,
     20    but WITHOUT ANY WARRANTY; without even the implied warranty of
     21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     22    GNU General Public License for more details.
     23 
     24    You should have received a copy of the GNU General Public License
     25    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
     26 
     27 #ifndef GDB_DWARF2_COMP_UNIT_HEAD_H
     28 #define GDB_DWARF2_COMP_UNIT_HEAD_H
     29 
     30 #include "dwarf2.h"
     31 #include "dwarf2/leb.h"
     32 #include "dwarf2/types.h"
     33 
     34 struct dwarf2_per_objfile;
     35 
     36 /* The data in a compilation unit header, after target2host
     37    translation, looks like this.  */
     38 struct comp_unit_head
     39 {
     40 private:
     41   unsigned int m_length = 0;
     42 public:
     43   unsigned char version = 0;
     44   unsigned char addr_size = 0;
     45   unsigned char signed_addr_p = 0;
     46   sect_offset abbrev_sect_off {};
     47 
     48   /* Size of file offsets; either 4 or 8.  */
     49   unsigned int offset_size = 0;
     50 
     51   /* Size of the length field; either 4 or 12.  */
     52   unsigned int initial_length_size = 0;
     53 
     54   enum dwarf_unit_type unit_type {};
     55 
     56   /* Offset to first die in this cu from the start of the cu.
     57      This will be the first byte following the compilation unit header.  */
     58   cu_offset first_die_cu_offset {};
     59 
     60   /* Offset to the first byte of this compilation unit header in the
     61      .debug_info section, for resolving relative reference dies.  */
     62   sect_offset sect_off {};
     63 
     64   /* For types, offset in the type's DIE of the type defined by this TU.  */
     65   cu_offset type_cu_offset_in_tu {};
     66 
     67   /* 64-bit signature of this unit. For type units, it denotes the signature of
     68      the type (DW_UT_type in DWARF 4, additionally DW_UT_split_type in DWARF 5).
     69      Also used in DWARF 5, to denote the dwo id when the unit type is
     70      DW_UT_skeleton or DW_UT_split_compile.  */
     71   ULONGEST signature = 0;
     72 
     73   void set_length (unsigned int length)
     74   {
     75     m_length = length;
     76   }
     77 
     78   /* Return the total length of the CU described by this header, including the
     79      initial length field.  */
     80   unsigned int get_length_with_initial () const
     81   {
     82     return m_length + initial_length_size;
     83   }
     84 
     85   /* Return the total length of the CU described by this header, excluding the
     86      initial length field.  */
     87   unsigned int get_length_without_initial () const
     88   {
     89     return m_length;
     90   }
     91 
     92   /* Return TRUE if OFF is within this CU.  */
     93   bool offset_in_cu_p (sect_offset off) const
     94   {
     95     sect_offset bottom = sect_off;
     96     sect_offset top = sect_off + get_length_with_initial ();
     97     return off >= bottom && off < top;
     98   }
     99 
    100   /* Read an offset from the data stream.  The size of the offset is
    101      given by cu_header->offset_size.  */
    102   LONGEST read_offset (bfd *abfd, const gdb_byte *buf,
    103 		       unsigned int *bytes_read) const
    104   {
    105     LONGEST offset = ::read_offset (abfd, buf, offset_size);
    106     *bytes_read = offset_size;
    107     return offset;
    108   }
    109 
    110   /* Read an address from BUF.  BYTES_READ is updated.  */
    111   unrelocated_addr read_address (bfd *abfd, const gdb_byte *buf,
    112 				 unsigned int *bytes_read) const;
    113 };
    114 
    115 /* Expected enum dwarf_unit_type for read_comp_unit_head.  */
    116 enum class rcuh_kind { COMPILE, TYPE };
    117 
    118 /* Read in the comp unit header information from the debug_info at info_ptr.
    119    Use rcuh_kind::COMPILE as the default type if not known by the caller.
    120    NOTE: This leaves members offset, first_die_offset to be filled in
    121    by the caller.  */
    122 extern const gdb_byte *read_comp_unit_head
    123   (struct comp_unit_head *cu_header,
    124    const gdb_byte *info_ptr,
    125    struct dwarf2_section_info *section,
    126    rcuh_kind section_kind);
    127 
    128 /* Read in a CU/TU header and perform some basic error checking.
    129    The contents of the header are stored in HEADER.
    130    The result is a pointer to the start of the first DIE.  */
    131 extern const gdb_byte *read_and_check_comp_unit_head
    132   (dwarf2_per_objfile *per_objfile,
    133    struct comp_unit_head *header,
    134    struct dwarf2_section_info *section,
    135    struct dwarf2_section_info *abbrev_section,
    136    const gdb_byte *info_ptr,
    137    rcuh_kind section_kind);
    138 
    139 #endif /* GDB_DWARF2_COMP_UNIT_HEAD_H */
    140