GAS: Do not create an entry for the default directory if the directory table is empty. Improve readelf's decoding of empty directory and file name tables.

PR 25917
	* dwarf.c (display_debug_lines_decoded): Warn if encountering a
	supicious number of entries for DWARF-5 format directory and file
	name tables.  Do not display file name table header if the table
	is empty.  Do not allocate space for empty tables.

binutils/ChangeLog

@@ -1,3 +1,11 @@
+2020-05-04  Nick Clifton  <nickc@redhat.com>
+
+	PR 25917
+	* dwarf.c (display_debug_lines_decoded): Warn if encountering a
+	supicious number of entries for DWARF-5 format directory and file
+	name tables.  Do not display file name table header if the table
+	is empty.  Do not allocate space for empty tables.
+
 2020-05-04  Alan Modra  <amodra@gmail.com>
 
 	* readelf.c (process_nds32_specific): Check size of .nds32_e_flags

binutils/dwarf.c

@@ -4343,6 +4343,8 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 
 	      /* Skip directories format.  */
 	      SAFE_BYTE_GET_AND_INC (format_count, data, 1, end);
+	      if (format_count > 1)
+		warn ("Unexpectedly large number of columns in the directory name table (%u)\n", format_count);
 	      format_start = data;
 	      for (formati = 0; formati < format_count; formati++)
 		{
@@ -4357,8 +4359,11 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 		  break;
 		}
 
-	      directory_table = (unsigned char **)
-		xmalloc (n_directories * sizeof (unsigned char *));
+	      if (n_directories == 0)
+		directory_table = NULL;
+	      else
+		directory_table = (unsigned char **)
+		  xmalloc (n_directories * sizeof (unsigned char *));
 
 	      for (entryi = 0; entryi < n_directories; entryi++)
 		{
@@ -4411,6 +4416,9 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 
 	      /* Skip files format.  */
 	      SAFE_BYTE_GET_AND_INC (format_count, data, 1, end);
+	      if (format_count > 5)
+		warn ("Unexpectedly large number of columns in the file name table (%u)\n", format_count);
+	      format_count = 2;
 	      format_start = data;
 	      for (formati = 0; formati < format_count; formati++)
 		{
@@ -4419,14 +4427,17 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 		}
 
 	      READ_ULEB (n_files, data, end);
-	      if (data == end)
+	      if (data == end && n_files > 0)
 		{
 		  warn (_("Corrupt file name list\n"));
 		  break;
 		}
 
-	      file_table = (File_Entry *) xcalloc (1, n_files
-						      * sizeof (File_Entry));
+	      if (n_files == 0)
+		file_table = NULL;
+	      else
+		file_table = (File_Entry *) xcalloc (1, n_files
+						     * sizeof (File_Entry));
 
 	      for (entryi = 0; entryi < n_files; entryi++)
 		{
@@ -4582,7 +4593,7 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 
 	  /* Print the Compilation Unit's name and a header.  */
 	  if (file_table == NULL)
-	    ;
+	    printf (_("CU: No directory table\n"));
 	  else if (directory_table == NULL)
 	    printf (_("CU: %s:\n"), file_table[0].name);
 	  else
@@ -4610,7 +4621,10 @@ display_debug_lines_decoded (struct dwarf_section *  section,
 		printf ("%s:\n", file_table[0].name);
 	    }
 
-	  printf (_("File name                            Line number    Starting address    View    Stmt\n"));
+	  if (n_files > 0)
+	    printf (_("File name                            Line number    Starting address    View    Stmt\n"));
+	  else
+	    printf (_("CU: Empty file name table\n"));
 	  saved_linfo = linfo;
 	}
 

gas/ChangeLog

@@ -1,3 +1,5 @@
+2020-05-04  Nick Clifton  <nickc@redhat.com>
+
 2020-05-04  Andre Vieira  <andre.simoesdiasvieira@arm.com>
 
 	PR gas/25863
@@ -10,6 +12,9 @@
 	PR 25917
 	* dwarf2dbg.c (out_dir_and_file_list): Check for the directory
 	table's existence before looking at its entries.
+	Also do not emit a default directory entry if there are no
+	directories in use.
+
 	* testsuite/gas/elf/pr25917.s: New test source file.
 	* testsuite/gas/elf/pr25917.d: New test driver.
 	* testsuite/gas/elf/elf.exp (run_elf_list_test): Run the new test.

gas/dwarf2dbg.c

@@ -1981,7 +1981,6 @@ out_dir_and_file_list (void)
   bfd_boolean emit_filesize = TRUE;
 
   /* Output the Directory Table.  */
-
   if (DWARF2_LINE_VERSION >= 5)
     {
       out_byte (1);
@@ -1993,7 +1992,7 @@ out_dir_and_file_list (void)
     }
       
   /* Emit directory list.  */
-  if (DWARF2_LINE_VERSION >= 5)
+  if (DWARF2_LINE_VERSION >= 5 && dirs_in_use > 0)
     {
       if (dirs == NULL || dirs[0] == NULL)
 	dir = remap_debug_filename (".");
@@ -2017,7 +2016,6 @@ out_dir_and_file_list (void)
     out_byte ('\0');
 
   /* Output the File Name Table.  */
-
   if (DWARF2_LINE_VERSION >= 5)
     {
       unsigned int columns = 4;
@@ -2045,7 +2043,6 @@ out_dir_and_file_list (void)
       
       /* The number of format entries to follow.  */
       out_byte (columns);
-
       /* The format of the file name.  */
       out_uleb128 (DW_LNCT_path);
       /* FIXME: it would be better to store these strings in