Add dwz.c and dwz_file::read_string

This changes read_indirect_string_from_dwz to be a method on the
dwz_file, and adds a new dwarf2/dwz.c file.

gdb/ChangeLog
2020-03-26  Tom Tromey  <tom@tromey.com>

	* dwarf2/read.c (read_attribute_value): Update.
	(read_indirect_string_from_dwz): Move to dwz.c; change into
	method.
	(dwarf_decode_macro_bytes): Update.
	* dwarf2/dwz.h (struct dwz_file) <read_string>: Declare method.
	* dwarf2/dwz.c: New file.
	* Makefile.in (COMMON_SFILES): Add dwz.c.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2020-03-26  Tom Tromey  <tom@tromey.com>
+
+	* dwarf2/read.c (read_attribute_value): Update.
+	(read_indirect_string_from_dwz): Move to dwz.c; change into
+	method.
+	(dwarf_decode_macro_bytes): Update.
+	* dwarf2/dwz.h (struct dwz_file) <read_string>: Declare method.
+	* dwarf2/dwz.c: New file.
+	* Makefile.in (COMMON_SFILES): Add dwz.c.
+
 2020-03-26  Tom Tromey  <tom@tromey.com>
 
 	* dwarf2/read.h (struct dwz_file): Move to dwz.h.

gdb/Makefile.in

@@ -1003,6 +1003,7 @@ COMMON_SFILES = \
 	dwarf2/abbrev.c \
 	dwarf2/attribute.c \
 	dwarf2/comp-unit.c \
+	dwarf2/dwz.c \
 	dwarf2/expr.c \
 	dwarf2/frame-tailcall.c \
 	dwarf2/frame.c \

gdb/dwarf2/dwz.c

@@ -0,0 +1,40 @@
+/* DWARF DWZ handling for GDB.
+
+   Copyright (C) 2003-2020 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "dwarf2/dwz.h"
+
+const char *
+dwz_file::read_string (struct objfile *objfile, LONGEST str_offset)
+{
+  str.read (objfile);
+
+  if (str.buffer == NULL)
+    error (_("DW_FORM_GNU_strp_alt used without .debug_str "
+	     "section [in module %s]"),
+	   bfd_get_filename (dwz_bfd.get ()));
+  if (str_offset >= str.size)
+    error (_("DW_FORM_GNU_strp_alt pointing outside of "
+	     ".debug_str section [in module %s]"),
+	   bfd_get_filename (dwz_bfd.get ()));
+  gdb_assert (HOST_CHAR_BIT == 8);
+  if (str.buffer[str_offset] == '\0')
+    return NULL;
+  return (const char *) (str.buffer + str_offset);
+}

gdb/dwarf2/dwz.h

@@ -53,6 +53,13 @@ struct dwz_file
   /* If we loaded the index from an external file, this contains the
      resources associated to the open file, memory mapping, etc.  */
   std::unique_ptr<index_cache_resource> index_cache_res;
+
+  /* Read a string at offset STR_OFFSET in the .debug_str section from
+     this dwz file.  Throw an error if the offset is too large.  If
+     the string consists of a single NUL byte, return NULL; otherwise
+     return a pointer to the string.  */
+
+  const char *read_string (struct objfile *objfile, LONGEST str_offset);
 };
 
 #endif /* GDB_DWARF2_DWZ_H */

gdb/dwarf2/read.c

@@ -1259,9 +1259,6 @@ static const char *read_indirect_string_at_offset
   (struct dwarf2_per_objfile *dwarf2_per_objfile, bfd *abfd,
    LONGEST str_offset);
 
-static const char *read_indirect_string_from_dwz
-  (struct objfile *objfile, struct dwz_file *, LONGEST);
-
 static CORE_ADDR read_addr_index_from_leb128 (struct dwarf2_cu *,
 					      const gdb_byte *,
 					      unsigned int *);
@@ -18585,8 +18582,7 @@ read_attribute_value (const struct die_reader_specs *reader,
 	LONGEST str_offset = cu_header->read_offset (abfd, info_ptr,
 						     &bytes_read);
 
-	DW_STRING (attr) = read_indirect_string_from_dwz (objfile,
-							  dwz, str_offset);
+	DW_STRING (attr) = dwz->read_string (objfile, str_offset);
 	DW_STRING_IS_CANONICAL (attr) = 0;
 	info_ptr += bytes_read;
       }
@@ -18831,31 +18827,6 @@ read_indirect_line_string_at_offset (struct dwarf2_per_objfile *dwarf2_per_objfi
 					      ".debug_line_str");
 }
 
-/* Read a string at offset STR_OFFSET in the .debug_str section from
-   the .dwz file DWZ.  Throw an error if the offset is too large.  If
-   the string consists of a single NUL byte, return NULL; otherwise
-   return a pointer to the string.  */
-
-static const char *
-read_indirect_string_from_dwz (struct objfile *objfile, struct dwz_file *dwz,
-			       LONGEST str_offset)
-{
-  dwz->str.read (objfile);
-
-  if (dwz->str.buffer == NULL)
-    error (_("DW_FORM_GNU_strp_alt used without .debug_str "
-	     "section [in module %s]"),
-	   bfd_get_filename (dwz->dwz_bfd.get ()));
-  if (str_offset >= dwz->str.size)
-    error (_("DW_FORM_GNU_strp_alt pointing outside of "
-	     ".debug_str section [in module %s]"),
-	   bfd_get_filename (dwz->dwz_bfd.get ()));
-  gdb_assert (HOST_CHAR_BIT == 8);
-  if (dwz->str.buffer[str_offset] == '\0')
-    return NULL;
-  return (const char *) (dwz->str.buffer + str_offset);
-}
-
 /* Return pointer to string at .debug_str offset as read from BUF.
    BUF is assumed to be in a compilation unit described by CU_HEADER.
    Return *BYTES_READ_PTR count of bytes read from BUF.  */
@@ -23584,8 +23555,7 @@ dwarf_decode_macro_bytes (struct dwarf2_cu *cu,
 		    struct dwz_file *dwz
 		      = dwarf2_get_dwz_file (dwarf2_per_objfile);
 
-		    body = read_indirect_string_from_dwz (objfile,
-							  dwz, str_offset);
+		    body = dwz->read_string (objfile, str_offset);
 		  }
 		else
 		  body = read_indirect_string_at_offset (dwarf2_per_objfile,