diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 0c6cdc653f5..7f150295798 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -3519,8 +3519,8 @@ sort_choices (std::vector<struct block_symbol> &syms)
 	       if (!b.symbol->is_objfile_owned ())
 		 return true;
 
-	       const char *fna = a.symbol->symtab ()->filename;
-	       const char *fnb = b.symbol->symtab ()->filename;
+	       const char *fna = a.symbol->symtab ()->filename ();
+	       const char *fnb = b.symbol->symtab ()->filename ();
 
 	       /* First sort by basename.  This is done because,
 		  depending on how GNAT was invoked, different sources
@@ -11927,7 +11927,7 @@ is_known_support_routine (const frame_info_ptr &frame)
   for (i = 0; known_runtime_file_name_patterns[i] != NULL; i += 1)
     {
       re_comp (known_runtime_file_name_patterns[i]);
-      if (re_exec (lbasename (sal.symtab->filename)))
+      if (re_exec (lbasename (sal.symtab->filename ())))
 	return 1;
       if (sal.symtab->compunit ()->objfile () != NULL
 	  && re_exec (objfile_name (sal.symtab->compunit ()->objfile ())))
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 1374481cc99..6656f393580 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -2228,7 +2228,7 @@ cmp_symtabs (const symtab_and_line &sala, const symtab_and_line &salb)
 	return r;
     }
 
-  r = filename_cmp (sala.symtab->filename, salb.symtab->filename);
+  r = filename_cmp (sala.symtab->filename (), salb.symtab->filename ());
   if (r)
     return r;
 
diff --git a/gdb/compile/compile-c-symbols.c b/gdb/compile/compile-c-symbols.c
index 65789775fc4..a71f84be52c 100644
--- a/gdb/compile/compile-c-symbols.c
+++ b/gdb/compile/compile-c-symbols.c
@@ -56,7 +56,7 @@ convert_one_symbol (compile_c_instance *context,
 		    int is_local)
 {
   gcc_type sym_type;
-  const char *filename = sym.symbol->symtab ()->filename;
+  const char *filename = sym.symbol->symtab ()->filename ();
   unsigned int line = sym.symbol->line ();
 
   context->error_symbol_once (sym.symbol);
diff --git a/gdb/compile/compile-cplus-symbols.c b/gdb/compile/compile-cplus-symbols.c
index 96ebd84887a..5b43ba1cc51 100644
--- a/gdb/compile/compile-cplus-symbols.c
+++ b/gdb/compile/compile-cplus-symbols.c
@@ -48,7 +48,7 @@ convert_one_symbol (compile_cplus_instance *instance,
 {
   /* Squash compiler warning.  */
   gcc_type sym_type = 0;
-  const char *filename = sym.symbol->symtab ()->filename;
+  const char *filename = sym.symbol->symtab ()->filename ();
   unsigned int line = sym.symbol->line ();
 
   instance->error_symbol_once (sym.symbol);
diff --git a/gdb/compile/compile-cplus-types.c b/gdb/compile/compile-cplus-types.c
index cf70fe484d7..66e5ddd36fc 100644
--- a/gdb/compile/compile-cplus-types.c
+++ b/gdb/compile/compile-cplus-types.c
@@ -624,7 +624,7 @@ compile_cplus_convert_struct_or_union_members
 		       we can do but ignore this member.  */
 		    continue;
 		  }
-		const char *filename = sym.symbol->symtab ()->filename;
+		const char *filename = sym.symbol->symtab ()->filename ();
 		unsigned int line = sym.symbol->line ();
 
 		physaddr = sym.symbol->value_address ();
@@ -763,7 +763,7 @@ compile_cplus_convert_struct_or_union_methods (compile_cplus_instance *instance,
 	      continue;
 	    }
 
-	  const char *filename = sym.symbol->symtab ()->filename;
+	  const char *filename = sym.symbol->symtab ()->filename ();
 	  unsigned int line = sym.symbol->line ();
 	  CORE_ADDR address = sym.symbol->value_block()->start ();
 	  const char *kind;
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 824479dd75a..81764e6b1a2 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -4842,7 +4842,7 @@ set_step_info (thread_info *tp, const frame_info_ptr &frame,
 
   infrun_debug_printf
     ("symtab = %s, line = %d, step_frame_id = %s, step_stack_frame_id = %s",
-     tp->current_symtab != nullptr ? tp->current_symtab->filename : "<null>",
+     tp->current_symtab != nullptr ? tp->current_symtab->filename () : "<null>",
      tp->current_line,
      tp->control.step_frame_id.to_string ().c_str (),
      tp->control.step_stack_frame_id.to_string ().c_str ());
diff --git a/gdb/linespec.c b/gdb/linespec.c
index 08f7fdd0daa..277b45b4b7f 100644
--- a/gdb/linespec.c
+++ b/gdb/linespec.c
@@ -2005,7 +2005,7 @@ create_sals_line_offset (struct linespec_state *self,
       set_default_source_symtab_and_line ();
       initialize_defaults (&self->default_symtab, &self->default_line);
       ls->file_symtabs
-	= collect_symtabs_from_filename (self->default_symtab->filename,
+	= collect_symtabs_from_filename (self->default_symtab->filename (),
 					 self->search_pspace);
       use_default = true;
     }
@@ -2291,7 +2291,7 @@ convert_linespec_to_sals (struct linespec_state *state, linespec *ls)
 	/* Make sure we have a filename for canonicalization.  */
 	if (ls->explicit_loc.source_filename == NULL)
 	  {
-	    const char *filename = state->default_symtab->filename;
+	    const char *filename = state->default_symtab->filename ();
 
 	    /* It may be more appropriate to keep DEFAULT_SYMTAB in its symtab
 	       form so that displaying SOURCE_FILENAME can follow the current
diff --git a/gdb/macroscope.c b/gdb/macroscope.c
index 563ef9931b3..32499fe5d21 100644
--- a/gdb/macroscope.c
+++ b/gdb/macroscope.c
@@ -51,7 +51,8 @@ sal_macro_scope (struct symtab_and_line sal)
   macro_scope ms;
 
   main_file = macro_main (cust->macro_table ());
-  inclusion = macro_lookup_inclusion (main_file, sal.symtab->filename_for_id);
+  inclusion = macro_lookup_inclusion (main_file,
+				      sal.symtab->filename_for_id ());
 
   if (inclusion)
     {
diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
index 9fd1fd013d2..7eb4e41a507 100644
--- a/gdb/python/py-breakpoint.c
+++ b/gdb/python/py-breakpoint.c
@@ -1644,7 +1644,7 @@ bploc_filepath (struct symtab *bploc_symtab)
     {
     }
 
-  return host_string_to_python_string (bploc_symtab->filename);
+  return host_string_to_python_string (bploc_symtab->filename ());
 }
 
 /* Python function to get the source file name path and line number
@@ -1763,7 +1763,7 @@ bplocpy_repr (PyObject *py_self)
 			  paddress (self->bp_loc->owner->gdbarch,
 				    self->bp_loc->requested_address));
   if (self->bp_loc->symtab != nullptr)
-    str += string_printf (" source=%s:%d", self->bp_loc->symtab->filename,
+    str += string_printf (" source=%s:%d", self->bp_loc->symtab->filename (),
 			  self->bp_loc->line_number);
 
   const auto fn_name = self->bp_loc->function_name.get ();
diff --git a/gdb/skip.c b/gdb/skip.c
index a9ee223c277..a56b3555d17 100644
--- a/gdb/skip.c
+++ b/gdb/skip.c
@@ -488,20 +488,20 @@ skiplist_entry::do_skip_file_p (const symtab_and_line &function_sal) const
   if (debug_skip)
     gdb_printf (gdb_stdlog,
 		"skip: checking if file %s matches non-glob %s...",
-		function_sal.symtab->filename, m_file.c_str ());
+		function_sal.symtab->filename (), m_file.c_str ());
 
   bool result;
 
   /* Check first sole SYMTAB->FILENAME.  It may not be a substring of
      symtab_to_fullname as it may contain "./" etc.  */
-  if (compare_filenames_for_search (function_sal.symtab->filename,
+  if (compare_filenames_for_search (function_sal.symtab->filename (),
 				    m_file.c_str ()))
     result = true;
 
   /* Before we invoke realpath, which can get expensive when many
      files are involved, do a quick comparison of the basenames.  */
   else if (!basenames_may_differ
-	   && filename_cmp (lbasename (function_sal.symtab->filename),
+	   && filename_cmp (lbasename (function_sal.symtab->filename ()),
 			    lbasename (m_file.c_str ())) != 0)
     result = false;
   else
@@ -524,13 +524,13 @@ skiplist_entry::do_skip_gfile_p (const symtab_and_line &function_sal) const
   if (debug_skip)
     gdb_printf (gdb_stdlog,
 		"skip: checking if file %s matches glob %s...",
-		function_sal.symtab->filename, m_file.c_str ());
+		function_sal.symtab->filename (), m_file.c_str ());
 
   bool result;
 
   /* Check first sole SYMTAB->FILENAME.  It may not be a substring of
      symtab_to_fullname as it may contain "./" etc.  */
-  if (gdb_filename_fnmatch (m_file.c_str (), function_sal.symtab->filename,
+  if (gdb_filename_fnmatch (m_file.c_str (), function_sal.symtab->filename (),
 			    FNM_NOESCAPE) == 0)
     result = true;
 
@@ -541,7 +541,7 @@ skiplist_entry::do_skip_gfile_p (const symtab_and_line &function_sal) const
      isn't much of a win.  Oh well.  */
   else if (!basenames_may_differ
       && gdb_filename_fnmatch (lbasename (m_file.c_str ()),
-			       lbasename (function_sal.symtab->filename),
+			       lbasename (function_sal.symtab->filename ()),
 			       FNM_NOESCAPE) != 0)
     result = false;
   else
diff --git a/gdb/source.c b/gdb/source.c
index e56f2b5d736..a47176cd9a5 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -342,7 +342,7 @@ select_source_symtab ()
 	{
 	  for (symtab *symtab : cu.filetabs ())
 	    {
-	      const char *name = symtab->filename;
+	      const char *name = symtab->filename ();
 	      int len = strlen (name);
 
 	      if (!(len > 2 && (strcmp (&name[len - 2], ".h") == 0
@@ -683,7 +683,7 @@ info_source_command (const char *ignore, int from_tty)
     }
 
   cust = s->compunit ();
-  gdb_printf (_("Current source file is %s\n"), s->filename);
+  gdb_printf (_("Current source file is %s\n"), s->filename ());
   if (s->compunit ()->dirname () != NULL)
     gdb_printf (_("Compilation directory is %s\n"), s->compunit ()->dirname ());
   if (s->fullname () != nullptr)
@@ -1119,7 +1119,8 @@ open_source_file (struct symtab *s)
     return scoped_fd (-EINVAL);
 
   gdb::unique_xmalloc_ptr<char> fullname = s->release_fullname ();
-  scoped_fd fd = find_and_open_source (s->filename, s->compunit ()->dirname (),
+  scoped_fd fd = find_and_open_source (s->filename (),
+				       s->compunit ()->dirname (),
 				       &fullname);
 
   if (fd.get () < 0)
@@ -1129,13 +1130,13 @@ open_source_file (struct symtab *s)
 	  const objfile *ofp = s->compunit ()->objfile ();
 
 	  std::string srcpath;
-	  if (IS_ABSOLUTE_PATH (s->filename))
-	    srcpath = s->filename;
+	  if (IS_ABSOLUTE_PATH (s->filename ()))
+	    srcpath = s->filename ();
 	  else if (s->compunit ()->dirname () != nullptr)
 	    {
 	      srcpath = s->compunit ()->dirname ();
 	      srcpath += SLASH_STRING;
-	      srcpath += s->filename;
+	      srcpath += s->filename ();
 	    }
 
 	  const struct bfd_build_id *build_id
@@ -1220,11 +1221,11 @@ symtab_to_fullname (struct symtab *s)
 	     should report the pathname where GDB tried to find the file.  */
 
 	  if (s->compunit ()->dirname () == nullptr
-	      || IS_ABSOLUTE_PATH (s->filename))
-	    fullname.reset (xstrdup (s->filename));
+	      || IS_ABSOLUTE_PATH (s->filename ()))
+	    fullname.reset (xstrdup (s->filename ()));
 	  else
 	    fullname.reset (concat (s->compunit ()->dirname (), SLASH_STRING,
-				    s->filename, (char *) NULL));
+				    s->filename (), (char *) NULL));
 
 	  s->set_fullname (rewrite_source_path (fullname.get ()));
 	  if (s->fullname () == nullptr)
@@ -1241,11 +1242,11 @@ const char *
 symtab_to_filename_for_display (struct symtab *symtab)
 {
   if (filename_display_string == filename_display_basename)
-    return lbasename (symtab->filename);
+    return lbasename (symtab->filename ());
   else if (filename_display_string == filename_display_absolute)
     return symtab_to_fullname (symtab);
   else if (filename_display_string == filename_display_relative)
-    return symtab->filename;
+    return symtab->filename ();
   else
     internal_error (_("invalid filename_display_string"));
 }
diff --git a/gdb/symfile-debug.c b/gdb/symfile-debug.c
index b402a87b7a7..e5ea7264997 100644
--- a/gdb/symfile-debug.c
+++ b/gdb/symfile-debug.c
@@ -184,7 +184,7 @@ iterate_over_one_compunit_symtab (const char *name,
 
   for (symtab *s : cust->filetabs ())
     {
-      if (compare_filenames_for_search (s->filename, name))
+      if (compare_filenames_for_search (s->filename (), name))
 	{
 	  if (callback (s))
 	    return true;
@@ -194,7 +194,7 @@ iterate_over_one_compunit_symtab (const char *name,
       /* Before we invoke realpath, which can get expensive when many
 	 files are involved, do a quick comparison of the basenames.  */
       if (! basenames_may_differ
-	  && FILENAME_CMP (base_name, lbasename (s->filename)) != 0)
+	  && FILENAME_CMP (base_name, lbasename (s->filename ())) != 0)
 	continue;
 
       if (compare_filenames_for_search (symtab_to_fullname (s), name))
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 806547d9d6f..85827cf3d49 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2830,11 +2830,11 @@ allocate_symtab (struct compunit_symtab *cust, const char *filename,
 {
   struct objfile *objfile = cust->objfile ();
   struct symtab *symtab
-    = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct symtab);
-
-  symtab->filename = objfile->intern (filename);
-  symtab->filename_for_id = objfile->intern (filename_for_id);
-  symtab->set_language (deduce_language_from_filename (filename));
+    = obstack_new<struct symtab> (&objfile->objfile_obstack,
+				  cust,
+				  objfile->intern (filename),
+				  objfile->intern (filename_for_id),
+				  deduce_language_from_filename (filename));
 
   /* This can be very verbose with lots of headers.
      Only print at higher debug levels.  */
@@ -2860,9 +2860,6 @@ allocate_symtab (struct compunit_symtab *cust, const char *filename,
   /* Add it to CUST's list of symtabs.  */
   cust->add_filetab (symtab);
 
-  /* Backlink to the containing compunit symtab.  */
-  symtab->set_compunit (cust);
-
   return symtab;
 }
 
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 3b0687c0750..3195cd2e2ae 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -3309,7 +3309,7 @@ find_line_symtab (symtab *sym_tab, int line, int *index)
 		  const struct linetable *l;
 		  int ind;
 
-		  if (FILENAME_CMP (sym_tab->filename, s->filename) != 0)
+		  if (FILENAME_CMP (sym_tab->filename (), s->filename ()) != 0)
 		    continue;
 		  if (FILENAME_CMP (symtab_to_fullname (sym_tab),
 				    symtab_to_fullname (s)) != 0)
@@ -4627,8 +4627,8 @@ symbol_search::compare_search_syms (const symbol_search &sym_a,
 {
   int c;
 
-  c = FILENAME_CMP (sym_a.symbol->symtab ()->filename,
-		    sym_b.symbol->symtab ()->filename);
+  c = FILENAME_CMP (sym_a.symbol->symtab ()->filename (),
+		    sym_b.symbol->symtab ()->filename ());
   if (c != 0)
     return c;
 
@@ -4802,9 +4802,9 @@ global_symbol_searcher::add_matching_symbols
 	      /* Check first sole REAL_SYMTAB->FILENAME.  It does
 		 not need to be a substring of symtab_to_fullname as
 		 it may contain "./" etc.  */
-	      if (!(file_matches (real_symtab->filename, m_filenames, false)
+	      if (!(file_matches (real_symtab->filename (), m_filenames, false)
 		    || ((basenames_may_differ
-			 || file_matches (lbasename (real_symtab->filename),
+			 || file_matches (lbasename (real_symtab->filename ()),
 					  m_filenames, true))
 			&& file_matches (symtab_to_fullname (real_symtab),
 					 m_filenames, false))))
@@ -6220,14 +6220,14 @@ make_source_files_completion_list (const char *text)
 	{
 	  for (symtab *s : cu.filetabs ())
 	    {
-	      if (not_interesting_fname (s->filename))
+	      if (not_interesting_fname (s->filename ()))
 		continue;
-	      if (!filenames_seen.seen (s->filename)
-		  && filename_ncmp (s->filename, text, text_len) == 0)
+	      if (!filenames_seen.seen (s->filename ())
+		  && filename_ncmp (s->filename (), text, text_len) == 0)
 		{
 		  /* This file matches for a completion; add it to the current
 		     list of matches.  */
-		  add_filename_to_list (s->filename, text, text, &list);
+		  add_filename_to_list (s->filename (), text, text, &list);
 		}
 	      else
 		{
@@ -6235,8 +6235,8 @@ make_source_files_completion_list (const char *text)
 		     debug info records leading directories, but not the other
 		     way around.  This is what subroutines of breakpoint
 		     command do when they parse file names.  */
-		  base_name = lbasename (s->filename);
-		  if (base_name != s->filename
+		  base_name = lbasename (s->filename ());
+		  if (base_name != s->filename ()
 		      && !filenames_seen.seen (base_name)
 		      && filename_ncmp (base_name, text, text_len) == 0)
 		    add_filename_to_list (base_name, text, text, &list);
diff --git a/gdb/symtab.h b/gdb/symtab.h
index e47033efd01..486b99d123a 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -1698,16 +1698,23 @@ typedef std::vector<CORE_ADDR> section_offsets;
 
 struct symtab
 {
+  symtab (struct compunit_symtab *cust, const char *filename,
+	  const char *filename_for_id, enum language language)
+    : m_filename (filename),
+      m_filename_for_id (filename_for_id),
+      m_compunit (cust),
+      m_language (language)
+  {
+    gdb_assert (m_filename != nullptr);
+    gdb_assert (m_filename_for_id != nullptr);
+    gdb_assert (m_compunit != nullptr);
+  }
+
   struct compunit_symtab *compunit () const
   {
     return m_compunit;
   }
 
-  void set_compunit (struct compunit_symtab *compunit)
-  {
-    m_compunit = compunit;
-  }
-
   const struct linetable *linetable () const
   {
     return m_linetable;
@@ -1749,16 +1756,24 @@ struct symtab
     m_fullname = name.release ();
   }
 
+  const char *filename () const
+  { return m_filename; }
+
+  const char *filename_for_id () const
+  { return m_filename_for_id; }
+
   /* Unordered chain of all filetabs in the compunit,  with the exception
      that the "main" source file is the first entry in the list.  */
 
-  struct symtab *next;
+  struct symtab *next = nullptr;
+
+private:
 
   /* Name of this source file, in a form appropriate to print to the user.
 
-     This pointer is never nullptr.  */
+     This pointer is never nullptr and is set from the constructor.  */
 
-  const char *filename;
+  const char *m_filename;
 
   /* Filename for this source file, used as an identifier to link with
      related objects such as associated macro_source_file objects.  It must
@@ -1767,28 +1782,29 @@ struct symtab
      follow that rule, or another form of the same file name, this is up to
      the specific debug info reader.
 
-     This pointer is never nullptr.*/
-  const char *filename_for_id;
+     This pointer is never nullptr, and is set from the constructor.  */
+  const char *m_filename_for_id;
 
-private:
+  /* Backlink to containing compunit symtab.
 
-  /* Backlink to containing compunit symtab.  */
+     This pointer is never nullptr, and is set from the constructor.  */
 
   struct compunit_symtab *m_compunit;
 
   /* Table mapping core addresses to line numbers for this file.
      Can be NULL if none.  Never shared between different symtabs.  */
 
-  const struct linetable *m_linetable;
+  const struct linetable *m_linetable = nullptr;
 
-  /* Language of this source file.  */
+  /* Language of this source file.  This is set in the object
+     constructor.  */
 
   enum language m_language;
 
   /* Full name of file as found by searching the source path.
      NULL if not yet known.  */
 
-  char *m_fullname;
+  char *m_fullname = nullptr;
 };
 
 /* A range adapter to allowing iterating over all the file tables in a list.  */