Re: [RFA 10/23] Remove make_cleanup_restore_current_language

Pedro Alves
2017-06-02T18:18:44Z

This is OK, but we may we want to take a closer look at
terminology -- we started with scoped_restore, and have added
other types called scoped_restore_whatever meanwhile.
But here we're calling it "save". It seems to me like it may be
better in the long run to pick one naming style for save/restore
types, and stick with it.

Thanks,
Pedro Alves

On 05/03/2017 11:46 PM, Tom Tromey wrote:
> This patch replaces make_cleanup_restore_current_language with an RAII
> class that saves the current language, and restores it when the object
> is destroyed.
>
> 2017-05-02 Tom Tromey <tom@tromey.com>
>
> * utils.h (make_cleanup_restore_current_language): Remove.
> * utils.c (do_restore_current_language)
> (make_cleanup_restore_current_language): Remove.
> * parse.c (parse_exp_in_context_1)
> (parse_expression_with_language): Use save_language.
> * mi/mi-main.c (mi_cmd_execute): Use save_language.
> * language.h (save_language): New class.
> ---
> gdb/ChangeLog | 10 ++++++++++
> gdb/language.h | 25 +++++++++++++++++++++++++
> gdb/mi/mi-main.c | 6 ++----
> gdb/parse.c | 22 +++++++---------------
> gdb/utils.c | 22 ----------------------
> gdb/utils.h | 2 --
> 6 files changed, 44 insertions(+), 43 deletions(-)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 50d8794..1c3b738 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,5 +1,15 @@
> 2017-05-02 Tom Tromey <tom@tromey.com>
>
> + * utils.h (make_cleanup_restore_current_language): Remove.
> + * utils.c (do_restore_current_language)
> + (make_cleanup_restore_current_language): Remove.
> + * parse.c (parse_exp_in_context_1)
> + (parse_expression_with_language): Use save_language.
> + * mi/mi-main.c (mi_cmd_execute): Use save_language.
> + * language.h (save_language): New class.
> +
> +2017-05-02 Tom Tromey <tom@tromey.com>
> +
> * source.c (get_filename_and_charpos, forward_search_command)
> (reverse_search_command): Use fd_closer.
> * procfs.c (load_syscalls, proc_get_LDT_entry)
> diff --git a/gdb/language.h b/gdb/language.h
> index 58bcbe8..f543da5 100644
> --- a/gdb/language.h
> +++ b/gdb/language.h
> @@ -609,4 +609,29 @@ void default_get_string (struct value *value, gdb_byte **buffer, int *length,
> void c_get_string (struct value *value, gdb_byte **buffer, int *length,
> struct type **char_type, const char **charset);
>
> +/* Save the current language and restore it upon destruction. */
> +
> +class save_language
> +{
> +public:
> +
> + explicit save_language (enum language new_lang)
> + : m_lang (current_language->la_language)
> + {
> + set_language (new_lang);
> + }
> +
> + ~save_language ()
> + {
> + set_language (m_lang);
> + }
> +
> + save_language (const save_language &) = delete;
> + save_language &operator= (const save_language &) = delete;
> +
> +private:
> +
> + enum language m_lang;
> +};
> +
> #endif /* defined (LANGUAGE_H) */
> diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> index cb68fd6..aa44876 100644
> --- a/gdb/mi/mi-main.c
> +++ b/gdb/mi/mi-main.c
> @@ -2242,11 +2242,9 @@ mi_cmd_execute (struct mi_parse *parse)
> error (_("Invalid frame id: %d"), frame);
> }
>
> + gdb::optional<save_language> lang_saver;
> if (parse->language != language_unknown)
> - {
> - make_cleanup_restore_current_language ();
> - set_language (parse->language);
> - }
> + lang_saver.emplace (parse->language);
>
> current_context = parse;
>
> diff --git a/gdb/parse.c b/gdb/parse.c
> index 3dd7075..84fce19 100644
> --- a/gdb/parse.c
> +++ b/gdb/parse.c
> @@ -50,6 +50,7 @@
> #include "objfiles.h"
> #include "user-regs.h"
> #include <algorithm>
> +#include "common/gdb_optional.h"
>
> /* Standard set of definitions for printing, dumping, prefixifying,
> * and evaluating expressions. */
> @@ -1136,7 +1137,7 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> const struct block *block,
> int comma, int void_context_p, int *out_subexp)
> {
> - struct cleanup *old_chain, *inner_chain;
> + struct cleanup *old_chain;
> const struct language_defn *lang = NULL;
> struct parser_state ps;
> int subexp;
> @@ -1214,8 +1215,8 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> to the value matching SELECTED_FRAME as set by get_current_arch. */
>
> initialize_expout (&ps, 10, lang, get_current_arch ());
> - inner_chain = make_cleanup_restore_current_language ();
> - set_language (lang->la_language);
> +
> + save_language lang_saver (lang->la_language);
>
> TRY
> {
> @@ -1250,7 +1251,6 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> if (expressiondebug)
> dump_prefix_expression (ps.expout, gdb_stdlog);
>
> - do_cleanups (inner_chain);
> discard_cleanups (old_chain);
>
> *stringptr = lexptr;
> @@ -1275,19 +1275,11 @@ parse_expression (const char *string)
> expression_up
> parse_expression_with_language (const char *string, enum language lang)
> {
> - struct cleanup *old_chain = NULL;
> -
> + gdb::optional<save_language> lang_saver;
> if (current_language->la_language != lang)
> - {
> - old_chain = make_cleanup_restore_current_language ();
> - set_language (lang);
> - }
> -
> - expression_up expr = parse_expression (string);
> + lang_saver.emplace (lang);
>
> - if (old_chain != NULL)
> - do_cleanups (old_chain);
> - return expr;
> + return parse_expression (string);
> }
>
> /* Parse STRING as an expression. If parsing ends in the middle of a
> diff --git a/gdb/utils.c b/gdb/utils.c
> index bffce78..1a66896 100644
> --- a/gdb/utils.c
> +++ b/gdb/utils.c
> @@ -307,28 +307,6 @@ make_cleanup_free_so (struct so_list *so)
> return make_cleanup (do_free_so, so);
> }
>
> -/* Helper for make_cleanup_restore_current_language. */
> -
> -static void
> -do_restore_current_language (void *p)
> -{
> - enum language saved_lang = (enum language) (uintptr_t) p;
> -
> - set_language (saved_lang);
> -}
> -
> -/* Remember the current value of CURRENT_LANGUAGE and make it restored when
> - the cleanup is run. */
> -
> -struct cleanup *
> -make_cleanup_restore_current_language (void)
> -{
> - enum language saved_lang = current_language->la_language;
> -
> - return make_cleanup (do_restore_current_language,
> - (void *) (uintptr_t) saved_lang);
> -}
> -
> /* Helper function for make_cleanup_clear_parser_state. */
>
> static void
> diff --git a/gdb/utils.h b/gdb/utils.h
> index 7afb3c5..1f01bdd 100644
> --- a/gdb/utils.h
> +++ b/gdb/utils.h
> @@ -91,8 +91,6 @@ extern struct cleanup *make_cleanup_value_free (struct value *);
> struct so_list;
> extern struct cleanup *make_cleanup_free_so (struct so_list *so);
>
> -extern struct cleanup *make_cleanup_restore_current_language (void);
> -
> /* A deleter for a hash table. */
> struct htab_deleter
> {
>