diff --git a/gcc/ada/gcc-interface/misc.c b/gcc/ada/gcc-interface/misc.c
index 96199bd4b63..87a4c8662cb 100644
--- a/gcc/ada/gcc-interface/misc.c
+++ b/gcc/ada/gcc-interface/misc.c
@@ -274,12 +274,6 @@ gnat_post_options (const char **pfilename ATTRIBUTE_UNUSED)
   if (!global_options_set.x_flag_diagnostics_show_caret)
     global_dc->show_caret = false;
 
-  /* Warn only if STABS is not the default: we don't want to emit a warning if
-     the user did not use a -gstabs option.  */
-  if (PREFERRED_DEBUGGING_TYPE != DBX_DEBUG && write_symbols == DBX_DEBUG)
-    warning (0, "STABS debugging information for Ada is obsolete and not "
-		"supported anymore");
-
   /* Copy global settings to local versions.  */
   gnat_encodings = global_options.x_gnat_encodings;
   optimize = global_options.x_optimize;
diff --git a/gcc/config/pa/som.h b/gcc/config/pa/som.h
index 05cc315b9f9..36a1122b132 100644
--- a/gcc/config/pa/som.h
+++ b/gcc/config/pa/som.h
@@ -21,6 +21,10 @@ along with GCC; see the file COPYING3.  If not see
 #undef TARGET_SOM
 #define TARGET_SOM 1
 
+/* With SOM we can only do STABS.  */
+#undef PREFERRED_DEBUGGING_TYPE
+#define PREFERRED_DEBUGGING_TYPE DBX_DEBUG
+
 /* We do not use BINCL stabs in SOM.
    ??? If it does not hurt, we probably should to avoid useless divergence
    from other embedded stabs implementations.  */
diff --git a/gcc/config/pdp11/pdp11.h b/gcc/config/pdp11/pdp11.h
index 9bc5e089f49..91a8ce70751 100644
--- a/gcc/config/pdp11/pdp11.h
+++ b/gcc/config/pdp11/pdp11.h
@@ -54,6 +54,9 @@ along with GCC; see the file COPYING3.  If not see
 
 #define DBX_DEBUGGING_INFO
 
+#undef PREFERRED_DEBUGGING_TYPE
+#define PREFERRED_DEBUGGING_TYPE DBX_DEBUG
+
 #define TARGET_40_PLUS		(TARGET_40 || TARGET_45)
 #define TARGET_10		(! TARGET_40_PLUS)
 
diff --git a/gcc/defaults.h b/gcc/defaults.h
index ba79a8e48ed..d7f2546f2cc 100644
--- a/gcc/defaults.h
+++ b/gcc/defaults.h
@@ -900,33 +900,14 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define DEFAULT_GDB_EXTENSIONS 1
 #endif
 
-/* If more than one debugging type is supported, you must define
-   PREFERRED_DEBUGGING_TYPE to choose the default.  */
-
-#if 1 < (defined (DBX_DEBUGGING_INFO) \
-         + defined (DWARF2_DEBUGGING_INFO) + defined (XCOFF_DEBUGGING_INFO) \
-         + defined (VMS_DEBUGGING_INFO))
+/* Default to DWARF2_DEBUGGING_INFO.  Legacy targets can choose different
+   by defining PREFERRED_DEBUGGING_TYPE.  */
 #ifndef PREFERRED_DEBUGGING_TYPE
-#error You must define PREFERRED_DEBUGGING_TYPE
-#endif /* no PREFERRED_DEBUGGING_TYPE */
-
-/* If only one debugging format is supported, define PREFERRED_DEBUGGING_TYPE
-   here so other code needn't care.  */
-#elif defined DBX_DEBUGGING_INFO
-#define PREFERRED_DEBUGGING_TYPE DBX_DEBUG
-
-#elif defined DWARF2_DEBUGGING_INFO || defined DWARF2_LINENO_DEBUGGING_INFO
+#if defined DWARF2_DEBUGGING_INFO || defined DWARF2_LINENO_DEBUGGING_INFO
 #define PREFERRED_DEBUGGING_TYPE DWARF2_DEBUG
-
-#elif defined VMS_DEBUGGING_INFO
-#define PREFERRED_DEBUGGING_TYPE VMS_AND_DWARF2_DEBUG
-
-#elif defined XCOFF_DEBUGGING_INFO
-#define PREFERRED_DEBUGGING_TYPE XCOFF_DEBUG
-
 #else
-/* No debugging format is supported by this target.  */
-#define PREFERRED_DEBUGGING_TYPE NO_DEBUG
+#error You must define PREFERRED_DEBUGGING_TYPE if DWARF is not supported
+#endif
 #endif
 
 #ifndef FLOAT_LIB_COMPARE_RETURNS_BOOL
diff --git a/gcc/testsuite/lib/prune.exp b/gcc/testsuite/lib/prune.exp
index fac212ecf60..131424861d5 100644
--- a/gcc/testsuite/lib/prune.exp
+++ b/gcc/testsuite/lib/prune.exp
@@ -93,6 +93,9 @@ proc prune_gcc_output { text } {
     # Ignore dsymutil warning (tool bug is actually linker)
     regsub -all "(^|\n)\[^\n\]*could not find object file symbol for symbol\[^\n\]*" $text "" text
 
+    # Ignore stabs obsoletion warnings
+    regsub -all "(^|\n)\[^\n\]*\[Ww\]arning: STABS debugging information is obsolete and not supported anymore\[^\n\]*" $text "" text
+
     # If dg-enable-nn-line-numbers was provided, then obscure source-margin
     # line numbers by converting them to "NN" form.
     set text [maybe-handle-nn-line-numbers $text]
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 14d1335e79e..8de8a92f2c6 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1452,6 +1452,11 @@ process_options (void)
       && ctf_debug_info_level == CTFINFO_LEVEL_NONE)
     write_symbols = NO_DEBUG;
 
+  /* Warn if STABS debug gets enabled and is not the default.  */
+  if (PREFERRED_DEBUGGING_TYPE != DBX_DEBUG && (write_symbols & DBX_DEBUG))
+    warning (0, "STABS debugging information is obsolete and not "
+	     "supported anymore");
+
   if (write_symbols == NO_DEBUG)
     ;
 #if defined(DBX_DEBUGGING_INFO)
