Avoid crash when global symbol table is empty with -fdump-fortran-global.

This just avoids a crash with -fdump-fortran-global when the
global symbol table is empty.  This is strictly a developer's
option, no user impact.

gcc/fortran/ChangeLog:

2020-06-14  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/42122
	* dump-parse-tree.c (gfc_dump_global_symbols):  If the symroot is
	empty, just output "empty".

diff --git a/gcc/fortran/dump-parse-tree.c b/gcc/fortran/dump-parse-tree.c
index f32330685e7a3f9e95d9110a4e3b4196641cbc07..f44648879f56fb6ab52222adeb7cc13a035edbfa 100644 (file)
--- a/gcc/fortran/dump-parse-tree.c
+++ b/gcc/fortran/dump-parse-tree.c
@@ -3595,5 +3595,8 @@ show_global_symbol (gfc_gsymbol *gsym, void *f_data)
 void
 gfc_dump_global_symbols (FILE *f)
 {
-  gfc_traverse_gsymbol (gfc_gsym_root, show_global_symbol, (void *) f);
+  if (gfc_gsym_root == NULL)
+    fprintf (f, "empty\n");
+  else
+    gfc_traverse_gsymbol (gfc_gsym_root, show_global_symbol, (void *) f);
 }