[gcc r12-4432] Always default to DWARF2_DEBUG if not specified, warn about deprecated STABS

[gcc r12-4432] Always default to DWARF2_DEBUG if not specified, warn about deprecated STABS

[Richard Biener]

https://gcc.gnu.org/g:7bfe7d634f60b0a9ba1a456be59a1ee88abf112e

commit r12-4432-g7bfe7d634f60b0a9ba1a456be59a1ee88abf112e
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Sep 10 11:25:21 2021 +0200

    Always default to DWARF2_DEBUG if not specified, warn about deprecated STABS
    
    This makes defaults.h choose DWARF2_DEBUG if PREFERRED_DEBUGGING_TYPE
    is not specified by the target and errors out if DWARF DWARF is not supported.
    
    It also makes us warn when STABS is enabled but not the preferred
    debugging type and removes the corresponding diagnostic from the Ada frontend.
    The warnings are pruned from the testsuite output via prune_gcc_output.
    
    The following target configurations now explicitely default to STABS:
     pdp11-*-*   pdp11 is a.out, dwarf support is difficult
     hppa[12]*-*-hpux10*  does not support DWARF
     hppa[12]*-*-hpux11*  likewise
    note that the hppa configs have been deprecated.
    
    Targets with DWARF support will now see
    > ./cc1 -quiet t.c -gstabs
    t.c: warning: STABS debugging information is obsolete and not supported anymore
    
    that is, -gstabs will still generate STABS but use will be diagnosed
    on targets where DWARF is available.
    
    I have built all targets from contrib/config-list.mk to make sure we
    don't run into the #error and the following makes the STABS usage
    explicit for pdp11 and hppa with SOM.
    
    This completes the series of deprecating STABS for GCC 12.
    
    2021-09-21  Richard Biener  <rguenther@suse.de>
    
    gcc/
            * defaults.h (PREFERRED_DEBUGGING_TYPE): Choose DWARF2_DEBUG
            when not set.
            * toplev.c (process_options): Warn when STABS debugging is
            enabled but not the preferred format.
            * config/pa/som.h (PREFERRED_DEBUGGING_TYPE): Define to
            DBX_DEBUG.
            * config/pdp11/pdp11.h (PREFERRED_DEBUGGING_TYPE): Likewise.
    
    gcc/ada/
            * gcc-interface/misc.c (gnat_post_options): Do not warn
            about DBX_DEBUG use here.
    
    gcc/testsuite/
            * lib/prune.exp: Prune STABS obsoletion message.

Diff:
---
 gcc/ada/gcc-interface/misc.c |  6 ------
 gcc/config/pa/som.h          |  4 ++++
 gcc/config/pdp11/pdp11.h     |  3 +++
 gcc/defaults.h               | 29 +++++------------------------
 gcc/testsuite/lib/prune.exp  |  3 +++
 gcc/toplev.c                 |  5 +++++
 6 files changed, 20 insertions(+), 30 deletions(-)

diff --git a/gcc/ada/gcc-interface/misc.c b/gcc/ada/gcc-interface/misc.c
index d0735708670..2caa83ff8cf 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 (!OPTION_SET_P (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 04d9bb12329..bb68d0d1a79 100644
--- a/gcc/defaults.h
+++ b/gcc/defaults.h
@@ -899,33 +899,14 @@ 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 4f574a5aad3..cb4f8c470f0 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1435,6 +1435,11 @@ process_options (bool no_backend)
       && 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)