Fix file-name handling regression with DWARF index

When run with the gdb-index or debug-names target boards, dup-psym.exp
fails.  This came up for me because my new DWARF scanner reuses this
part of the existing index code, and so it registers as a regression.
This is PR symtab/25834.

Looking into this, I found that the DWARF index code here is fairly
different from the psymtab code.  I don't think there's a deep reason
for this, and in fact, it seemed to me that the index code could
simply mimic what the psymtab code already does.

That is what this patch implements.  The DW_AT_name and DW_AT_comp_dir
are now stored in the quick file names table.  This may require
allocating a quick file names table even when DW_AT_stmt_list does not
exist.  Then, the functions that work with this data are changed to
use find_source_or_rewrite, just as the psymbol code does.  Finally,
line_header::file_full_name is removed, as it is no longer needed.

Currently, the index maintains a hash table of "quick file names".
The hash table uses a deletion function to free the "real name"
components when necessary.  There's also a second such function to
implement the forget_cached_source_info method.

This bug fix patch will create a quick file name object even when
there is no DW_AT_stmt_list, meaning that the object won't be entered
in the hash table.  So, this patch changes the memory management
approach so that the entries are cleared when the per-BFD object is
destroyed.  (A dwarf2_per_cu_data destructor is not introduced,
because we have been avoiding adding a vtable to that class.)

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=25834

gdb/dwarf2/line-header.c

@@ -96,25 +96,6 @@ line_header::file_file_name (int file) const
     }
 }
 
-gdb::unique_xmalloc_ptr<char>
-line_header::file_full_name (int file, const char *comp_dir) const
-{
-  /* Is the file number a valid index into the line header's file name
-     table?  Remember that file numbers start with one, not zero.  */
-  if (is_valid_file_index (file))
-    {
-      gdb::unique_xmalloc_ptr<char> relative = file_file_name (file);
-
-      if (IS_ABSOLUTE_PATH (relative.get ()) || comp_dir == NULL)
-	return relative;
-      return gdb::unique_xmalloc_ptr<char> (concat (comp_dir, SLASH_STRING,
-						    relative.get (),
-						    (char *) NULL));
-    }
-  else
-    return file_file_name (file);
-}
-
 static void
 dwarf2_statement_list_fits_in_line_number_section_complaint (void)
 {

gdb/dwarf2/line-header.h

@@ -162,13 +162,6 @@ struct line_header
      header.  These point into dwarf2_per_objfile->line_buffer.  */
   const gdb_byte *statement_program_start {}, *statement_program_end {};
 
-  /* Return the full name of file number I in this object's file name
-     table.  Use COMP_DIR as the name of the current directory of the
-     compilation.  The result is allocated using xmalloc; the caller
-     is responsible for freeing it.  */
-  gdb::unique_xmalloc_ptr<char> file_full_name (int file,
-						const char *comp_dir) const;
-
   /* Return file name relative to the compilation directory of file
      number I in this object's file name table.  The result is
      allocated using xmalloc; the caller is responsible for freeing

gdb/dwarf2/read.c

@@ -1542,6 +1542,12 @@ struct file_and_directory
 static file_and_directory find_file_and_directory (struct die_info *die,
 						   struct dwarf2_cu *cu);
 
+static const char *compute_include_file_name
+     (const struct line_header *lh,
+      const file_entry &fe,
+      const file_and_directory &cu_info,
+      gdb::unique_xmalloc_ptr<char> *name_holder);
+
 static htab_up allocate_signatured_type_table ();
 
 static htab_up allocate_dwo_unit_table ();
@@ -1654,7 +1660,10 @@ dwarf2_per_bfd::dwarf2_per_bfd (bfd *obfd, const dwarf2_debug_sections *names,
 dwarf2_per_bfd::~dwarf2_per_bfd ()
 {
   for (auto &per_cu : all_comp_units)
-    per_cu->imported_symtabs_free ();
+    {
+      per_cu->imported_symtabs_free ();
+      per_cu->free_cached_file_names ();
+    }
 
   /* Everything else should be on this->obstack.  */
 }
@@ -1966,6 +1975,10 @@ struct quick_file_names
   /* The number of entries in file_names, real_names.  */
   unsigned int num_file_names;
 
+  /* The CU directory, as given by DW_AT_comp_dir.  May be
+     nullptr.  */
+  const char *comp_dir;
+
   /* The file names from the line table, after being run through
      file_full_name.  */
   const char **file_names;
@@ -2162,25 +2175,6 @@ eq_file_name_entry (const void *a, const void *b)
   return eq_stmt_list_entry (&ea->hash, &eb->hash);
 }
 
-/* Delete function for a quick_file_names.  */
-
-static void
-delete_file_name_entry (void *e)
-{
-  struct quick_file_names *file_data = (struct quick_file_names *) e;
-  int i;
-
-  for (i = 0; i < file_data->num_file_names; ++i)
-    {
-      xfree ((void*) file_data->file_names[i]);
-      if (file_data->real_names)
-	xfree ((void*) file_data->real_names[i]);
-    }
-
-  /* The space for the struct itself lives on the obstack, so we don't
-     free it here.  */
-}
-
 /* Create a quick_file_names hash table.  */
 
 static htab_up
@@ -2188,7 +2182,7 @@ create_quick_file_names_table (unsigned int nr_initial_entries)
 {
   return htab_up (htab_create_alloc (nr_initial_entries,
 				     hash_file_name_entry, eq_file_name_entry,
-				     delete_file_name_entry, xcalloc, xfree));
+				     nullptr, xcalloc, xfree));
 }
 
 /* Read in CU (dwarf2_cu object) for PER_CU in the context of PER_OBJFILE.  This
@@ -2930,30 +2924,50 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
 
       lh = dwarf_decode_line_header (line_offset, cu);
     }
-  if (lh == NULL)
-    return;
-
-  qfn = XOBNEW (&per_objfile->per_bfd->obstack, struct quick_file_names);
-  qfn->hash.dwo_unit = cu->dwo_unit;
-  qfn->hash.line_sect_off = line_offset;
-  gdb_assert (slot != NULL);
-  *slot = qfn;
 
   file_and_directory fnd = find_file_and_directory (comp_unit_die, cu);
 
   int offset = 0;
   if (strcmp (fnd.name, "<unknown>") != 0)
     ++offset;
+  else if (lh == nullptr)
+    return;
 
-  qfn->num_file_names = offset + lh->file_names_size ();
+  qfn = XOBNEW (&per_objfile->per_bfd->obstack, struct quick_file_names);
+  qfn->hash.dwo_unit = cu->dwo_unit;
+  qfn->hash.line_sect_off = line_offset;
+  /* There may not be a DW_AT_stmt_list.  */
+  if (slot != nullptr)
+    *slot = qfn;
+
+  std::vector<const char *> include_names;
+  if (lh != nullptr)
+    {
+      for (const auto &entry : lh->file_names ())
+	{
+	  gdb::unique_xmalloc_ptr<char> name_holder;
+	  const char *include_name =
+	    compute_include_file_name (lh.get (), entry, fnd, &name_holder);
+	  if (include_name != nullptr)
+	    {
+	      include_name = per_objfile->objfile->intern (include_name);
+	      include_names.push_back (include_name);
+	    }
+	}
+    }
+
+  qfn->num_file_names = offset + include_names.size ();
+  qfn->comp_dir = fnd.comp_dir;
   qfn->file_names =
     XOBNEWVEC (&per_objfile->per_bfd->obstack, const char *,
 	       qfn->num_file_names);
   if (offset != 0)
     qfn->file_names[0] = xstrdup (fnd.name);
-  for (int i = 0; i < lh->file_names_size (); ++i)
-    qfn->file_names[i + offset] = lh->file_full_name (i + 1,
-						      fnd.comp_dir).release ();
+
+  if (!include_names.empty ())
+    memcpy (&qfn->file_names[offset], include_names.data (),
+	    include_names.size () * sizeof (const char *));
+
   qfn->real_names = NULL;
 
   lh_cu->v.quick->file_names = qfn;
@@ -2993,7 +3007,17 @@ dw2_get_real_path (dwarf2_per_objfile *per_objfile,
 				      qfn->num_file_names, const char *);
 
   if (qfn->real_names[index] == NULL)
-    qfn->real_names[index] = gdb_realpath (qfn->file_names[index]).release ();
+    {
+      const char *dirname = nullptr;
+
+      if (!IS_ABSOLUTE_PATH (qfn->file_names[index]))
+	dirname = qfn->comp_dir;
+
+      gdb::unique_xmalloc_ptr<char> fullname;
+      fullname = find_source_or_rewrite (qfn->file_names[index], dirname);
+
+      qfn->real_names[index] = fullname.release ();
+    }
 
   return qfn->real_names[index];
 }
@@ -3012,25 +3036,23 @@ dwarf2_base_index_functions::find_last_source_symtab (struct objfile *objfile)
   return compunit_primary_filetab (cust);
 }
 
-/* Traversal function for dw2_forget_cached_source_info.  */
+/* See read.h.  */
 
-static int
-dw2_free_cached_file_names (void **slot, void *info)
+void
+dwarf2_per_cu_data::free_cached_file_names ()
 {
-  struct quick_file_names *file_data = (struct quick_file_names *) *slot;
+  if (per_bfd == nullptr || !per_bfd->using_index || v.quick == nullptr)
+    return;
 
-  if (file_data->real_names)
+  struct quick_file_names *file_data = v.quick->file_names;
+  if (file_data != nullptr && file_data->real_names != nullptr)
     {
-      int i;
-
-      for (i = 0; i < file_data->num_file_names; ++i)
+      for (int i = 0; i < file_data->num_file_names; ++i)
 	{
-	  xfree ((void*) file_data->real_names[i]);
-	  file_data->real_names[i] = NULL;
+	  xfree ((void *) file_data->real_names[i]);
+	  file_data->real_names[i] = nullptr;
 	}
     }
-
-  return 1;
 }
 
 void
@@ -3039,8 +3061,8 @@ dwarf2_base_index_functions::forget_cached_source_info
 {
   dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
 
-  htab_traverse_noresize (per_objfile->per_bfd->quick_file_names_table.get (),
-			  dw2_free_cached_file_names, NULL);
+  for (auto &per_cu : per_objfile->per_bfd->all_comp_units)
+    per_cu->free_cached_file_names ();
 }
 
 /* Struct used to manage iterating over all CUs looking for a symbol.  */
@@ -4444,18 +4466,19 @@ dwarf2_base_index_functions::map_symbol_filenames
       for (int j = 0; j < file_data->num_file_names; ++j)
 	{
 	  const char *filename = file_data->file_names[j];
-	  filenames_cache.seen (filename);
+	  const char *key = filename;
+	  const char *fullname = nullptr;
+
+	  if (need_fullname)
+	    {
+	      fullname = dw2_get_real_path (per_objfile, file_data, j);
+	      key = fullname;
+	    }
+
+	  if (!filenames_cache.seen (key))
+	    fun (filename, fullname);
 	}
     }
-
-  filenames_cache.traverse ([&] (const char *filename)
-    {
-      gdb::unique_xmalloc_ptr<char> this_real_name;
-
-      if (need_fullname)
-	this_real_name = gdb_realpath (filename);
-      fun (filename, this_real_name.get ());
-    });
 }
 
 bool

gdb/dwarf2/read.h

@@ -275,6 +275,9 @@ struct dwarf2_per_cu_data
   {
     return section == nullptr;
   }
+
+  /* Free any cached file names.  */
+  void free_cached_file_names ();
 };
 
 /* Entry in the signatured_types hash table.  */