Re: [PATCH 1/2] gdb, gdbserver, gdbsupport: use [[maybe_unused]] instead of ATTRIBUTE_UNUSED

[Tom de Vries <tdevries@suse.de>]

On 6/18/26 7:50 PM, simon.marchi@polymtl.ca wrote:
> From: Simon Marchi <simon.marchi@polymtl.ca>
> 
> Since we require C++17, replace the uses of the ATTRIBUTE_UNUSED macro
> (which expands to __attribute__ ((__unused__))) with the standard
> [[maybe_unused]] attribute.
> 
> I think that some of these attribute uses are not necessary, but I did
> not make an attempt to remove them, that would be for another patch.
> 

Hi,

these both look fine to me.

Reviewed-By: Tom de Vries <tdevries@suse.de>

Thanks,
- Tom

> Change-Id: I62529d94153c65e2b3c49ff5330292e60c8a0f9e
> ---
>   gdb/inferior.c                       | 4 ++--
>   gdb/inflow.c                         | 2 +-
>   gdb/linux-fork.c                     | 2 +-
>   gdb/mi/mi-interp.c                   | 2 +-
>   gdb/python/py-utils.c                | 2 +-
>   gdb/remote.c                         | 2 +-
>   gdb/source-cache.c                   | 6 +++---
>   gdb/thread.c                         | 4 ++--
>   gdb/typeprint.c                      | 4 ++--
>   gdb/unittests/enum-flags-selftests.c | 4 ++--
>   gdb/valprint.c                       | 4 ++--
>   gdbserver/linux-aarch64-low.cc       | 6 +++---
>   gdbserver/x86-tdesc.h                | 4 ++--
>   gdbsupport/safe-strerror.cc          | 4 ++--
>   gdbsupport/thread-pool.cc            | 6 +++---
>   15 files changed, 28 insertions(+), 28 deletions(-)
> 
> diff --git a/gdb/inferior.c b/gdb/inferior.c
> index 1481f46cdd18..7d54845f28ac 100644
> --- a/gdb/inferior.c
> +++ b/gdb/inferior.c
> @@ -432,7 +432,7 @@ find_inferior_for_program_space (struct program_space *pspace)
>   int
>   have_inferiors (void)
>   {
> -  for (inferior *inf ATTRIBUTE_UNUSED : all_non_exited_inferiors ())
> +  for ([[maybe_unused]] inferior *inf : all_non_exited_inferiors ())
>       return 1;
>   
>     return 0;
> @@ -449,7 +449,7 @@ number_of_live_inferiors (process_stratum_target *proc_target)
>   
>     for (inferior *inf : all_non_exited_inferiors (proc_target))
>       if (inf->has_execution ())
> -      for (thread_info &tp ATTRIBUTE_UNUSED : inf->non_exited_threads ())
> +      for ([[maybe_unused]] thread_info &tp : inf->non_exited_threads ())
>   	{
>   	  /* Found a live thread in this inferior, go to the next
>   	     inferior.  */
> diff --git a/gdb/inflow.c b/gdb/inflow.c
> index c40ad2cf5294..e3a080dbd657 100644
> --- a/gdb/inflow.c
> +++ b/gdb/inflow.c
> @@ -493,7 +493,7 @@ child_terminal_ours_1 (target_terminal_state desired_state)
>   
>     if (gdb_tty_state != desired_state)
>       {
> -      int result ATTRIBUTE_UNUSED;
> +      [[maybe_unused]] int result;
>   
>         /* Ignore SIGTTOU since it will happen when we try to set the
>   	 terminal's pgrp.  */
> diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
> index 92afa4dde6db..fac35e13afb8 100644
> --- a/gdb/linux-fork.c
> +++ b/gdb/linux-fork.c
> @@ -963,7 +963,7 @@ inf_has_multiple_threads ()
>   
>     /* Return true as soon as we see the second thread of the current
>        inferior.  */
> -  for (thread_info &tp ATTRIBUTE_UNUSED : current_inferior ()->threads ())
> +  for ([[maybe_unused]] thread_info &tp : current_inferior ()->threads ())
>       if (++count > 1)
>         return true;
>   
> diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
> index 1a0d34106ed1..998409563e97 100644
> --- a/gdb/mi/mi-interp.c
> +++ b/gdb/mi/mi-interp.c
> @@ -637,7 +637,7 @@ static bool
>   multiple_inferiors_p ()
>   {
>     int count = 0;
> -  for (inferior *inf ATTRIBUTE_UNUSED : all_non_exited_inferiors ())
> +  for ([[maybe_unused]] inferior *inf : all_non_exited_inferiors ())
>       {
>         count++;
>         if (count > 1)
> diff --git a/gdb/python/py-utils.c b/gdb/python/py-utils.c
> index a831b96eb387..3979343acde9 100644
> --- a/gdb/python/py-utils.c
> +++ b/gdb/python/py-utils.c
> @@ -314,7 +314,7 @@ gdb_py_int_as_long (PyObject *obj, long *result)
>   
>   PyObject *
>   gdb_py_generic_dict_getter (PyObject *self,
> -			    void *closure ATTRIBUTE_UNUSED)
> +			    [[maybe_unused]] void *closure)
>   {
>     PyObject **py_dict_ptr = gdbpy_dict_wrapper::compute_addr (self);
>     PyObject *py_dict = *py_dict_ptr;
> diff --git a/gdb/remote.c b/gdb/remote.c
> index f8c7383cb037..43df087b83b3 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -4546,7 +4546,7 @@ static bool
>   has_single_non_exited_thread (inferior *inf)
>   {
>     int count = 0;
> -  for (thread_info &tp ATTRIBUTE_UNUSED : inf->non_exited_threads ())
> +  for ([[maybe_unused]] thread_info &tp : inf->non_exited_threads ())
>       if (++count > 1)
>         break;
>     return count == 1;
> diff --git a/gdb/source-cache.c b/gdb/source-cache.c
> index 6e8acab35044..0a64745ee585 100644
> --- a/gdb/source-cache.c
> +++ b/gdb/source-cache.c
> @@ -199,9 +199,9 @@ get_language_name (enum language lang)
>      succeeded.  */
>   
>   static bool
> -try_source_highlight (std::string &contents ATTRIBUTE_UNUSED,
> -		      enum language lang ATTRIBUTE_UNUSED,
> -		      const std::string &fullname ATTRIBUTE_UNUSED)
> +try_source_highlight ([[maybe_unused]] std::string &contents,
> +		      [[maybe_unused]] enum language lang,
> +		      [[maybe_unused]] const std::string &fullname)
>   {
>   #ifdef HAVE_SOURCE_HIGHLIGHT
>     if (!use_gnu_source_highlight)
> diff --git a/gdb/thread.c b/gdb/thread.c
> index 96c733e0629b..ffb980546b93 100644
> --- a/gdb/thread.c
> +++ b/gdb/thread.c
> @@ -476,7 +476,7 @@ thread_step_over_chain_length (const thread_step_over_list &l)
>   {
>     int num = 0;
>   
> -  for (const thread_info &thread ATTRIBUTE_UNUSED : l)
> +  for ([[maybe_unused]] const thread_info &thread : l)
>       ++num;
>   
>     return num;
> @@ -626,7 +626,7 @@ find_thread (find_thread_callback_ftype callback)
>   bool
>   any_thread_p ()
>   {
> -  for (thread_info &tp ATTRIBUTE_UNUSED : all_threads ())
> +  for ([[maybe_unused]] thread_info &tp : all_threads ())
>       return true;
>     return false;
>   }
> diff --git a/gdb/typeprint.c b/gdb/typeprint.c
> index 31a9c1814a31..01c6c218a5d5 100644
> --- a/gdb/typeprint.c
> +++ b/gdb/typeprint.c
> @@ -516,11 +516,11 @@ ptype_command (const char *type_name, int from_tty)
>   }
>   
>   /* Meant to be used in debug sessions, so don't export it in a header file.  */
> -extern void ATTRIBUTE_UNUSED debug_type (struct type *type);
> +[[maybe_unused]] extern void debug_type (struct type *type);
>   
>   /* Print TYPE.  */
>   
> -void ATTRIBUTE_UNUSED
> +[[maybe_unused]] void
>   debug_type (struct type *type)
>   {
>     type_print (type, "", gdb_stdlog, 1);
> diff --git a/gdb/unittests/enum-flags-selftests.c b/gdb/unittests/enum-flags-selftests.c
> index bf748e873035..ca404bfa3ebe 100644
> --- a/gdb/unittests/enum-flags-selftests.c
> +++ b/gdb/unittests/enum-flags-selftests.c
> @@ -70,8 +70,8 @@ static_assert (std::is_trivially_copyable<EnumFlag>::value);
>      below.  Their names (and types) match the uppercase type names
>      exposed by CHECK_VALID just to make the expressions easier to
>      follow.  */
> -static RawEnum re ATTRIBUTE_UNUSED;
> -static EnumFlag ef ATTRIBUTE_UNUSED;
> +[[maybe_unused]] static RawEnum re;
> +[[maybe_unused]] static EnumFlag ef;
>   
>   /* First, compile-time tests that:
>   
> diff --git a/gdb/valprint.c b/gdb/valprint.c
> index 50a4663ca3b5..67bfbf589301 100644
> --- a/gdb/valprint.c
> +++ b/gdb/valprint.c
> @@ -1232,11 +1232,11 @@ value_print (struct value *val, struct ui_file *stream,
>   }
>   
>   /* Meant to be used in debug sessions, so don't export it in a header file.  */
> -extern void ATTRIBUTE_UNUSED debug_val (struct value *val);
> +[[maybe_unused]] extern void debug_val (struct value *val);
>   
>   /* Print VAL.  */
>   
> -void ATTRIBUTE_UNUSED
> +[[maybe_unused]] void
>   debug_val (struct value *val)
>   {
>     value_print (val, gdb_stdlog, &user_print_options);
> diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
> index a2588a6e2a9c..b68d39e1b803 100644
> --- a/gdbserver/linux-aarch64-low.cc
> +++ b/gdbserver/linux-aarch64-low.cc
> @@ -741,7 +741,7 @@ aarch64_target::low_new_fork (process_info *parent,
>   
>   static void
>   aarch64_sve_regs_copy_to_regcache (struct regcache *regcache,
> -				   ATTRIBUTE_UNUSED const void *buf)
> +				   [[maybe_unused]] const void *buf)
>   {
>     /* BUF is unused here since we collect the data straight from a ptrace
>        request in aarch64_sve_regs_copy_to_reg_buf, therefore bypassing
> @@ -776,7 +776,7 @@ aarch64_sve_regs_copy_from_regcache (struct regcache *regcache, void *buf)
>   
>   static void
>   aarch64_za_regs_copy_to_regcache (struct regcache *regcache,
> -				  ATTRIBUTE_UNUSED const void *buf)
> +				  [[maybe_unused]] const void *buf)
>   {
>     /* BUF is unused here since we collect the data straight from a ptrace
>        request, therefore bypassing gdbserver's own call to ptrace.  */
> @@ -822,7 +822,7 @@ aarch64_za_regs_copy_from_regcache (struct regcache *regcache, void *buf)
>   
>   static void
>   aarch64_zt_regs_copy_to_regcache (struct regcache *regcache,
> -				  ATTRIBUTE_UNUSED const void *buf)
> +				  [[maybe_unused]] const void *buf)
>   {
>     /* BUF is unused here since we collect the data straight from a ptrace
>        request, therefore bypassing gdbserver's own call to ptrace.  */
> diff --git a/gdbserver/x86-tdesc.h b/gdbserver/x86-tdesc.h
> index 4ed6d6635bbb..ce0c6c1be90d 100644
> --- a/gdbserver/x86-tdesc.h
> +++ b/gdbserver/x86-tdesc.h
> @@ -20,8 +20,8 @@
>   
>   /* The "expedite" registers for x86 targets.  Since whether the
>      variable is used depends on host/configuration, we mark it
> -   ATTRIBUTE_UNUSED to keep it simple here.  */
> -static const char *i386_expedite_regs[] ATTRIBUTE_UNUSED
> +   [[maybe_unused]] to keep it simple here.  */
> +[[maybe_unused]] static const char *i386_expedite_regs[]
>       = {"ebp", "esp", "eip", NULL};
>   
>   #ifdef __x86_64__
> diff --git a/gdbsupport/safe-strerror.cc b/gdbsupport/safe-strerror.cc
> index d53cf84511fd..ad25cfc3d765 100644
> --- a/gdbsupport/safe-strerror.cc
> +++ b/gdbsupport/safe-strerror.cc
> @@ -26,14 +26,14 @@
>      function.  */
>   
>   /* Called if we have a XSI-compliant strerror_r.  */
> -ATTRIBUTE_UNUSED static char *
> +[[maybe_unused]] static char *
>   select_strerror_r (int res, char *buf)
>   {
>     return res == 0 ? buf : nullptr;
>   }
>   
>   /* Called if we have a GNU strerror_r.  */
> -ATTRIBUTE_UNUSED static char *
> +[[maybe_unused]] static char *
>   select_strerror_r (char *res, char *)
>   {
>     return res;
> diff --git a/gdbsupport/thread-pool.cc b/gdbsupport/thread-pool.cc
> index 4dc72e566428..12329ea98831 100644
> --- a/gdbsupport/thread-pool.cc
> +++ b/gdbsupport/thread-pool.cc
> @@ -44,14 +44,14 @@
>      takes a printf-style format and an argument.  This wrapper handles the
>      difference.  */
>   
> -ATTRIBUTE_UNUSED static void
> +[[maybe_unused]] static void
>   do_set_thread_name (int (*set_name) (pthread_t, const char *, void *),
>   		    const char *name)
>   {
>     set_name (pthread_self (), "%s", const_cast<char *> (name));
>   }
>   
> -ATTRIBUTE_UNUSED static void
> +[[maybe_unused]] static void
>   do_set_thread_name (int (*set_name) (pthread_t, const char *),
>   		    const char *name)
>   {
> @@ -60,7 +60,7 @@ do_set_thread_name (int (*set_name) (pthread_t, const char *),
>   
>   /* The macOS man page says that pthread_setname_np returns "void", but
>      the headers actually declare it returning "int".  */
> -ATTRIBUTE_UNUSED static void
> +[[maybe_unused]] static void
>   do_set_thread_name (int (*set_name) (const char *), const char *name)
>   {
>     set_name (name);
> 
> base-commit: cdfda31c0d6b85cfff7fddeabffa570176161548