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(-)

gdb/contrib/gdb-add-index.sh

@@ -37,11 +37,15 @@ fi
 
 dir="${file%/*}"
 test "$dir" = "$file" && dir="."
-index="${file}.gdb-index"
+index4="${file}.gdb-index"
+index5="${file}.debug_names"
+debugstr="${file}.debug_str"
+debugstrmerge="${file}.debug_str.merge"
+debugstrerr="${file}.debug_str.err"
 
-rm -f $index
+rm -f $index4 $index5 $debugstr $debugstrmerge $debugstrerr
 # Ensure intermediate index file is removed when we exit.
-trap "rm -f $index" 0
+trap "rm -f $index4 $index5 $debugstr $debugstrmerge $debugstrerr" 0
 
 $GDB --batch -nx -iex 'set auto-load no' \
     -ex "file $file" -ex "save gdb-index $dir" || {
@@ -57,9 +61,46 @@ $GDB --batch -nx -iex 'set auto-load no' \
 # already stripped binary, it's a no-op.
 status=0
 
-if test -f "$index"; then
-    $OBJCOPY --add-section .gdb_index="$index" \
-	--set-section-flags .gdb_index=readonly "$file" "$file"
+if test -f "$index4" -a -f "$index5"; then
+    echo "$myname: Both index types were created for $file" 1>&2
+    status=1
+elif test -f "$index4" -o -f "$index5"; then
+    if test -f "$index4"; then
+	index="$index4"
+	section=".gdb_index"
+    else
+	index="$index5"
+	section=".debug_names"
+    fi
+    debugstradd=false
+    debugstrupdate=false
+    if test -s "$debugstr"; then
+	if ! $OBJCOPY --dump-section .debug_str="$debugstrmerge" "$file" /dev/null \
+		 2>$debugstrerr; then
+	    cat >&2 $debugstrerr
+	    exit 1
+	fi
+	if grep -q "can't dump section '.debug_str' - it does not exist" \
+		  $debugstrerr; then
+	    debugstradd=true
+	else
+	    debugstrupdate=true
+	    cat >&2 $debugstrerr
+	fi
+	cat "$debugstr" >>"$debugstrmerge"
+    fi
+
+    $OBJCOPY --add-section $section="$index" \
+	--set-section-flags $section=readonly \
+	$(if $debugstradd; then \
+	      echo --add-section .debug_str="$debugstrmerge"; \
+	      echo --set-section-flags .debug_str=readonly; \
+	  fi; \
+	  if $debugstrupdate; then \
+	      echo --update-section .debug_str="$debugstrmerge"; \
+	  fi) \
+	"$file" "$file"
+
     status=$?
 else
     echo "$myname: No index was created for $file" 1>&2