On Fri, Jul 9, 2021 at 12:23 AM Indu Bhagat via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hello,
>
> It was brought up when discussing PR debug/101283 (Several tests fail on
> Darwin with -gctf/gbtf) that it will be good to provide means for targets to
> opt out of CTF/BTF support.
>
> By and large, it seems to me that CTF/BTF debug formats can be safely enabled
> for all ELF-based targets by default in GCC.
>
> So, at a high level:
> - By default, CTF/BTF formats can be enabled for all ELF-based targets.
> - By default, CTF/BTF formats can be disabled for all non ELF-based targets.
> - If the user passed a -gctf but CTF is not enabled for the target, GCC
> issues an error to the user (as is done currently with other debug formats)
> -
> "target system does not support the 'ctf' debug format".
>
> This is a makeshift patch which fulfills the above requirements and is based
> on
> the approach taken for DWARF via DWARF2_DEBUGGING_INFO (I still have to see if
> I need some specific handling in common_handle_option in opts.c). On minimal
> testing, the patch works as desired on x86_64-pc-linux-gnu and a darwin-based
> target.
>
> My question is - Looking around in config.gcc etc., it seems defining in
> elfos.h
> gives targets/platforms means to override it by virtue of the recommended
> order
> of # includes in $tm_file. What I cannot say for certain is if this is true in
> practice ? On first look, I believe this could work fine. What do you think ?
>
> If you think this approach could work, I will continue on this track and
> test/refine the patch.
I think it looks reasonable. Note that target macros need to be documented
in tm.texi - I think while we generally do not want new target macros but
hooks this case can be an exception for consistency purposes (unless
somebody else strongly disagrees).
Thanks,
Richard.
> Thanks
> Indu
>
> -------------
>
> gcc/ChangeLog:
>
> * config/elfos.h (CTF_DEBUGGING_INFO): New definition.
> (BTF_DEBUGGING_INFO): Likewise.
> * toplev.c: Guard initialization of debug hooks.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/debug/btf/btf.exp: Do not run BTF testsuite if target does
> not
> support BTF format.
> * gcc.dg/debug/ctf/ctf.exp: Do not run CTF testsuite if target does
> not
> support CTF format.
> ---
> gcc/config/elfos.h | 8 ++++++++
> gcc/testsuite/gcc.dg/debug/btf/btf.exp | 11 +++++++++--
> gcc/testsuite/gcc.dg/debug/ctf/ctf.exp | 11 +++++++++--
> gcc/toplev.c | 11 +++++++++--
> 4 files changed, 35 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/config/elfos.h b/gcc/config/elfos.h
> index 7a736cc..e5cb487 100644
> --- a/gcc/config/elfos.h
> +++ b/gcc/config/elfos.h
> @@ -68,6 +68,14 @@ see the files COPYING3 and COPYING.RUNTIME respectively.
> If not, see
>
> #define DWARF2_DEBUGGING_INFO 1
>
> +/* All ELF targets can support CTF. */
> +
> +#define CTF_DEBUGGING_INFO 1
> +
> +/* All ELF targets can support BTF. */
> +
> +#define BTF_DEBUGGING_INFO 1
> +
> /* The GNU tools operate better with dwarf2, and it is required by some
> psABI's. Since we don't have any native tools to be compatible with,
> default to dwarf2. */
> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf.exp
> b/gcc/testsuite/gcc.dg/debug/btf/btf.exp
> index e173515..a3e680c 100644
> --- a/gcc/testsuite/gcc.dg/debug/btf/btf.exp
> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf.exp
> @@ -39,8 +39,15 @@ if ![info exists DEFAULT_CFLAGS] then {
> dg-init
>
> # Main loop.
> -dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\] ]] \
> - "" $DEFAULT_CFLAGS
> +set comp_output [gcc_target_compile \
> + "$srcdir/$subdir/../trivial.c" "trivial.S" assembly \
> + "additional_flags=-gbtf"]
> +if { ! [string match "*: target system does not support the * debug format*"
> \
> + $comp_output] } {
> + remove-build-file "trivial.S"
> + dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\] ]] \
> + "" $DEFAULT_CFLAGS
> +}
>
> # All done.
> dg-finish
> diff --git a/gcc/testsuite/gcc.dg/debug/ctf/ctf.exp
> b/gcc/testsuite/gcc.dg/debug/ctf/ctf.exp
> index 0b650ed..c53cd8b 100644
> --- a/gcc/testsuite/gcc.dg/debug/ctf/ctf.exp
> +++ b/gcc/testsuite/gcc.dg/debug/ctf/ctf.exp
> @@ -39,8 +39,15 @@ if ![info exists DEFAULT_CFLAGS] then {
> dg-init
>
> # Main loop.
> -dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\] ]] \
> - "" $DEFAULT_CFLAGS
> +set comp_output [gcc_target_compile \
> + "$srcdir/$subdir/../trivial.c" "trivial.S" assembly \
> + "additional_flags=-gctf"]
> +if { ! [string match "*: target system does not support the * debug format*"
> \
> + $comp_output] } {
> + remove-build-file "trivial.S"
> + dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\] ]] \
> + "" $DEFAULT_CFLAGS
> +}
>
> # All done.
> dg-finish
> diff --git a/gcc/toplev.c b/gcc/toplev.c
> index 43f1f7d..8103812 100644
> --- a/gcc/toplev.c
> +++ b/gcc/toplev.c
> @@ -1463,8 +1463,15 @@ process_options (void)
> debug_hooks = &xcoff_debug_hooks;
> #endif
> #ifdef DWARF2_DEBUGGING_INFO
> - else if (dwarf_debuginfo_p ()
> - || dwarf_based_debuginfo_p ())
> + else if (dwarf_debuginfo_p ())
> + debug_hooks = &dwarf2_debug_hooks;
> +#endif
> +#ifdef CTF_DEBUGGING_INFO
> + else if (write_symbols & CTF_DEBUG)
> + debug_hooks = &dwarf2_debug_hooks;
> +#endif
> +#ifdef BTF_DEBUGGING_INFO
> + else if (btf_debuginfo_p ())
> debug_hooks = &dwarf2_debug_hooks;
> #endif
> #ifdef VMS_DEBUGGING_INFO
> --
> 1.8.3.1
>
