Re: [PATCH] Always default to DWARF2_DEBUG if not specified, warn about deprecated STABS

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Sep 21, 2021 at 4:26 PM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> 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 t.c: warning: STABS debugging information is obsolete and not supported anymore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.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> OK for trunk?

Ping.

> Thanks,
> Richard.
>
> 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.
> ---
>  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 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)
> --
> 2.31.1