DWARF-5: .debug_names index producer

This adds a new "-dwarf-5" switch to "save gdb-index" that makes it
generate index files with DWARF-5 .debug_names/.debug_str sections
instead of GDB's own .gdb_index.

We should probably add a command line option to
contrib/gdb-add-index.sh (incl. cc-with-tweaks.sh) for the new
-dwarf-5 GDB option, and a new target board to make it more convenient
to exercise this.  To be done later.

gdb/ChangeLog
2017-12-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* contrib/gdb-add-index.sh (index): Rename to ...
	(index4): ... here.
	(index5, debugstr, debugstrmerge, debugstrerr): New variables.
	Support also .debug_names and .debug_str.
	* dwarf2read.c: Include cmath, set, list.
	(INDEX_SUFFIX): Rename to ...
	(INDEX4_SUFFIX): ... here.
	(INDEX5_SUFFIX, DEBUG_STR_SUFFIX): New.
	(file_write(FILE *, const void *, size_t)): New.
	(file_write(FILE *, const std::vector<Elem, Alloc> &)): New.
	(data_buf::append_unsigned_leb128, data_buf::empty): New.
	(data_buf::file_write): Use ::file_write.
	(data_buf::c_str, dwarf5_djb_hash, debug_names)
	(check_dwarf64_offsets): New.
	(psyms_seen_size, write_gdbindex): New from
	write_psymtabs_to_index code.
	(dwarf5_gdb_augmentation, write_debug_names, assert_file_size)
	(enum dw_index_kind): New.
	(write_psymtabs_to_index): New parameter index_kind.  Support
	filename_str and out_file_str.  Move code to write_gdbindex,
	possibly call write_debug_names.
	(save_gdb_index_command): New parameter -dwarf-5.
	(_initialize_dwarf2_read): Document the new parameter -dwarf-5.

gdb/doc/ChangeLog
2017-12-08  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.texinfo (Index Files): Document .debug_names and -dwarf-5.
--

 gdb/contrib/gdb-add-index.sh |   53 ++
 gdb/doc/gdb.texinfo          |   24 +
 gdb/dwarf2read.c             |  919 ++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 935 insertions(+), 61 deletions(-)

2 files changed, 23 insertions, 5 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index df294d6..7710640 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,7 @@
+2017-12-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	* gdb.texinfo (Index Files): Document .debug_names and -dwarf-5.
+
 2017-12-07  Keith Seitz  <keiths@redhat.com>
 
 	* gdb.texinfo (Symbols): Document "set print type nested-type-limit"
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 1e4ef98..062f01d 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -19565,12 +19565,16 @@ using @command{objcopy}.
 To create an index file, use the @code{save gdb-index} command:
 
 @table @code
-@item save gdb-index @var{directory}
+@item save gdb-index [-dwarf-5] @var{directory}
 @kindex save gdb-index
-Create an index file for each symbol file currently known by
-@value{GDBN}.  Each file is named after its corresponding symbol file,
-with @samp{.gdb-index} appended, and is written into the given
-@var{directory}.
+Create index files for all symbol files currently known by
+@value{GDBN}.  For each known @var{symbol-file}, this command by
+default creates it produces a single file
+@file{@var{symbol-file}.gdb-index}.  If you invoke this command with
+the @option{-dwarf-5} option, it produces 2 files:
+@file{@var{symbol-file}.debug_names} and
+@file{@var{symbol-file}.debug_str}.  The files are created in the
+given @var{directory}.
 @end table
 
 Once you have created an index file you can merge it into your symbol
@@ -19581,6 +19585,16 @@ $ objcopy --add-section .gdb_index=symfile.gdb-index \
     --set-section-flags .gdb_index=readonly symfile symfile
 @end smallexample
 
+Or for @code{-dwarf-5}:
+
+@smallexample
+$ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
+$ cat symfile.debug_str >>symfile.debug_str.new
+$ objcopy --add-section .debug_names=symfile.gdb-index \
+    --set-section-flags .debug_names=readonly \
+    --update-section .debug_str=symfile.debug_str.new symfile symfile
+@end smallexample
+
 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
 sections that have been deprecated.  Usually they are deprecated because
 they are missing a new feature or have performance issues.