Add support for a ".file 0" directive if supporting DWARF 5 or higher.

PR 25614
	* dwarf2dbg.c (dwarf2_directive_filename): Allow a file number of
	0 if the dwarf_level is 5 or more.  Complain if a filename follows
	a file 0.
	* testsuite/gas/elf/dwarf-5-file0.s: New test.
	* testsuite/gas/elf/dwarf-5-file0.d: New test driver.
	* testsuite/gas/elf/elf.exp: Run the new test.

	PR 25612
	* config/tc-ia64.h (DWARF2_VERISION): Fix typo.
	* doc/as.texi: Fix another typo.

gas/ChangeLog

@@ -1,3 +1,17 @@
+2020-03-06  Nick Clifton  <nickc@redhat.com>
+
+	PR 25614
+	* dwarf2dbg.c (dwarf2_directive_filename): Allow a file number of
+	0 if the dwarf_level is 5 or more.  Complain if a filename follows
+	a file 0.
+	* testsuite/gas/elf/dwarf-5-file0.s: New test.
+	* testsuite/gas/elf/dwarf-5-file0.d: New test driver.
+	* testsuite/gas/elf/elf.exp: Run the new test.
+
+	PR 25612
+	* config/tc-ia64.h (DWARF2_VERISION): Fix typo.
+	* doc/as.texi: Fix another typo.
+
 2020-03-06  Nick Clifton  <nickc@redhat.com>
 
 	PR 25612

gas/config/tc-ia64.h

@@ -325,5 +325,5 @@ typedef struct unwind_record
 
 /* VMS backtraces expect dwarf version 3.  */
 #ifdef TE_VMS
-#define DWARF2_VERSION      (dwarf_level < 3 ? 3  : debug_level)
+#define DWARF2_VERSION      (dwarf_level < 3 ? 3  : dwarf_level)
 #endif

gas/doc/as.texi

@@ -780,7 +780,7 @@ per target basis.
 @item --gdwarf-5
 This option is the same as the @option{--gdwarf-2} option, except that it
 allows for the possibility of the generation of extra debug information as per
-version 4 of the DWARF specification.  Note - enabling this option does not
+version 5 of the DWARF specification.  Note - enabling this option does not
 guarantee the generation of any extra infortmation, the choice to do so is on a
 per target basis.
 

gas/dwarf2dbg.c

@@ -794,17 +794,27 @@ dwarf2_directive_filename (void)
     }
 
   num = get_absolute_expression ();
-  filename = demand_copy_C_string (&filename_len);
-  if (filename == NULL)
-    return NULL;
-  demand_empty_rest_of_line ();
 
-  if ((offsetT) num < 1)
+  if ((offsetT) num < 1 && dwarf_level < 5)
     {
       as_bad (_("file number less than one"));
+      ignore_rest_of_line ();
       return NULL;
     }
 
+  if (num == 0)
+    {
+      demand_empty_rest_of_line ();
+      return NULL;
+    }
+
+  filename = demand_copy_C_string (&filename_len);
+  if (filename == NULL)
+    /* demand_copy_C_string will have already generated an error message.  */
+    return NULL;
+
+  demand_empty_rest_of_line ();
+
   /* A .file directive implies compiler generated debug information is
      being supplied.  Turn off gas generated debug info.  */
   debug_type = DEBUG_NONE;
@@ -821,7 +831,7 @@ dwarf2_directive_filename (void)
       return NULL;
     }
 
-  get_filenum (filename, (unsigned int) num);
+  (void) get_filenum (filename, (unsigned int) num);
 
   return filename;
 }

gas/testsuite/gas/elf/dwarf-5-file0.d

@@ -0,0 +1,6 @@
+#as: --gdwarf-5
+#name: DWARF5 .line 0
+#readelf: -wl
+
+#pass
+

gas/testsuite/gas/elf/dwarf-5-file0.s

@@ -0,0 +1,18 @@
+	.text
+
+.file 0
+.line 1
+	.long 3
+
+.file 1 "asdf"
+.line 2
+	.long 5
+
+.file 0
+.line 4
+	.long 3
+
+.file 2 "def"
+.line 5
+	.long 3
+

gas/testsuite/gas/elf/elf.exp

@@ -272,6 +272,7 @@ if { [is_elf_format] } then {
     run_dump_test "dwarf2-17" $dump_opts
     run_dump_test "dwarf2-18" $dump_opts
     run_dump_test "dwarf2-19" $dump_opts
+    run_dump_test "dwarf-5-file0" $dump_opts
     run_dump_test "bss"
     run_dump_test "bad-bss"
     run_dump_test "bad-section-flag"