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Re: [RFA] C++-ify parser_state
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Tom Tromey <tom at tromey dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Mon, 27 Nov 2017 09:16:55 -0500
- Subject: Re: [RFA] C++-ify parser_state
- Authentication-results: sourceware.org; auth=none
- References: <20171126174047.23943-1-tom@tromey.com>
On Sunday, November 26 2017, Tom Tromey wrote:
> This mildly C++-ifies parser_state and stap_parse_info -- just enough
> to remove some cleanups.
Thanks for the patch, Tom.
This was on my TODO list for a while now. I looked it over and it seems
good to me.
> Regression tested by the buildbot.
>
> ChangeLog
> 2017-11-26 Tom Tromey <tom@tromey.com>
>
> * stap-probe.h (struct stap_parse_info): Add constructor,
> destructor.
> * stap-probe.c (stap_parse_argument): Update.
> * rust-exp.y (rust_lex_tests): Update.
> * parser-defs.h (struct parser_state): Add constructor,
> destructor, release method.
> (initialize_expout, reallocate_expout): Remove.
> * parse.c (parser_state::parser_state): Rename from
> initialize_expout.
> (parser_state::~parser_state): New.
> (parser_state::release): Rename from reallocate_expout.
> (parse_exp_in_context_1): Update.
> * dtrace-probe.c (dtrace_probe::build_arg_exprs): Update.
> ---
> gdb/ChangeLog | 16 ++++++++++++++
> gdb/dtrace-probe.c | 11 ++--------
> gdb/parse.c | 63 ++++++++++++++++++++++++++++++------------------------
> gdb/parser-defs.h | 32 +++++++++++++--------------
> gdb/rust-exp.y | 3 +--
> gdb/stap-probe.c | 15 ++-----------
> gdb/stap-probe.h | 17 +++++++++++++++
> 7 files changed, 88 insertions(+), 69 deletions(-)
>
> diff --git a/gdb/dtrace-probe.c b/gdb/dtrace-probe.c
> index 1c88f89054..c0134dcac5 100644
> --- a/gdb/dtrace-probe.c
> +++ b/gdb/dtrace-probe.c
> @@ -626,21 +626,15 @@ dtrace_probe::build_arg_exprs (struct gdbarch *gdbarch)
> value of the argument when executed at the PC of the probe. */
> for (dtrace_probe_arg &arg : m_args)
> {
> - struct cleanup *back_to;
> - struct parser_state pstate;
> -
> /* Initialize the expression buffer in the parser state. The
> language does not matter, since we are using our own
> parser. */
> - initialize_expout (&pstate, 10, current_language, gdbarch);
> - back_to = make_cleanup (free_current_contents, &pstate.expout);
> + parser_state pstate (10, current_language, gdbarch);
>
> /* The argument value, which is ABI dependent and casted to
> `long int'. */
> gdbarch_dtrace_parse_probe_argument (gdbarch, &pstate, argc);
>
> - discard_cleanups (back_to);
> -
> /* Casting to the expected type, but only if the type was
> recognized at probe load time. Otherwise the argument will
> be evaluated as the long integer passed to the probe. */
> @@ -651,8 +645,7 @@ dtrace_probe::build_arg_exprs (struct gdbarch *gdbarch)
> write_exp_elt_opcode (&pstate, UNOP_CAST);
> }
>
> - reallocate_expout (&pstate);
> - arg.expr = expression_up (pstate.expout);
> + arg.expr = pstate.release ();
> prefixify_expression (arg.expr.get ());
> ++argc;
> }
> diff --git a/gdb/parse.c b/gdb/parse.c
> index 506efa38fb..3a7b7af4e1 100644
> --- a/gdb/parse.c
> +++ b/gdb/parse.c
> @@ -152,34 +152,43 @@ end_arglist (void)
>
> /* See definition in parser-defs.h. */
>
> -void
> -initialize_expout (struct parser_state *ps, size_t initial_size,
> - const struct language_defn *lang,
> - struct gdbarch *gdbarch)
> +parser_state::parser_state (size_t initial_size,
> + const struct language_defn *lang,
> + struct gdbarch *gdbarch)
> + : expout_size (initial_size),
> + expout_ptr (0)
> {
> - ps->expout_size = initial_size;
> - ps->expout_ptr = 0;
> - ps->expout
> + expout
> = (struct expression *) xmalloc (sizeof (struct expression)
> - + EXP_ELEM_TO_BYTES (ps->expout_size));
> - ps->expout->language_defn = lang;
> - ps->expout->gdbarch = gdbarch;
> + + EXP_ELEM_TO_BYTES (expout_size));
> + expout->language_defn = lang;
> + expout->gdbarch = gdbarch;
> }
>
> /* See definition in parser-defs.h. */
>
> -void
> -reallocate_expout (struct parser_state *ps)
> +parser_state::~parser_state ()
> +{
> + xfree (expout);
> +}
> +
> +expression_up
> +parser_state::release ()
> {
> /* Record the actual number of expression elements, and then
> reallocate the expression memory so that we free up any
> excess elements. */
>
> - ps->expout->nelts = ps->expout_ptr;
> - ps->expout = (struct expression *)
> - xrealloc (ps->expout,
> + expout->nelts = expout_ptr;
> + expout = (struct expression *)
> + xrealloc (expout,
> sizeof (struct expression)
> - + EXP_ELEM_TO_BYTES (ps->expout_ptr));
> + + EXP_ELEM_TO_BYTES (expout_ptr));
> +
> + expression_up result (expout);
> + /* Ensure that we don't free it in the destructor. */
> + expout = nullptr;
> + return result;
> }
>
> /* This page contains the functions for adding data to the struct expression
> @@ -1118,7 +1127,6 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> int comma, int void_context_p, int *out_subexp)
> {
> const struct language_defn *lang = NULL;
> - struct parser_state ps;
> int subexp;
>
> lexptr = *stringptr;
> @@ -1194,7 +1202,7 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> and others called from *.y) ensure CURRENT_LANGUAGE gets restored
> to the value matching SELECTED_FRAME as set by get_current_arch. */
>
> - initialize_expout (&ps, 10, lang, get_current_arch ());
> + parser_state ps (10, lang, get_current_arch ());
>
> scoped_restore_current_language lang_saver;
> set_language (lang->la_language);
> @@ -1207,33 +1215,32 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
> CATCH (except, RETURN_MASK_ALL)
> {
> if (! parse_completion)
> - {
> - xfree (ps.expout);
> - throw_exception (except);
> - }
> + throw_exception (except);
> }
> END_CATCH
>
> - reallocate_expout (&ps);
> + /* We have to operate on an "expression *", due to la_post_parser,
> + which explains this funny-looking double release. */
> + struct expression *result = ps.release ().release ();
>
> /* Convert expression from postfix form as generated by yacc
> parser, to a prefix form. */
>
> if (expressiondebug)
> - dump_raw_expression (ps.expout, gdb_stdlog,
> + dump_raw_expression (result, gdb_stdlog,
> "before conversion to prefix form");
>
> - subexp = prefixify_expression (ps.expout);
> + subexp = prefixify_expression (result);
> if (out_subexp)
> *out_subexp = subexp;
>
> - lang->la_post_parser (&ps.expout, void_context_p);
> + lang->la_post_parser (&result, void_context_p);
>
> if (expressiondebug)
> - dump_prefix_expression (ps.expout, gdb_stdlog);
> + dump_prefix_expression (result, gdb_stdlog);
>
> *stringptr = lexptr;
> - return expression_up (ps.expout);
> + return expression_up (result);
> }
>
> /* Parse STRING as an expression, and complain if this fails
> diff --git a/gdb/parser-defs.h b/gdb/parser-defs.h
> index f43fb75df2..262b81b056 100644
> --- a/gdb/parser-defs.h
> +++ b/gdb/parser-defs.h
> @@ -37,6 +37,21 @@ extern int parser_debug;
>
> struct parser_state
> {
> + /* Constructor. INITIAL_SIZE is the initial size of the expout
> + array. LANG is the language used to parse the expression. And
> + GDBARCH is the gdbarch to use during parsing. */
> +
> + parser_state (size_t initial_size, const struct language_defn *lang,
> + struct gdbarch *gdbarch);
> + ~parser_state ();
> +
> + DISABLE_COPY_AND_ASSIGN (parser_state);
> +
> + /* Resize the allocated expression to the correct size, and return
> + it as an expression_up -- passing ownership to the caller. */
> + expression_up release ();
> +
> +
> /* The expression related to this parser state. */
>
> struct expression *expout;
> @@ -156,23 +171,6 @@ struct type_stack
> int size;
> };
>
> -/* Helper function to initialize the expout, expout_size, expout_ptr
> - trio inside PS before it is used to store expression elements created
> - during the parsing of an expression. INITIAL_SIZE is the initial size of
> - the expout array. LANG is the language used to parse the expression.
> - And GDBARCH is the gdbarch to use during parsing. */
> -
> -extern void initialize_expout (struct parser_state *ps,
> - size_t initial_size,
> - const struct language_defn *lang,
> - struct gdbarch *gdbarch);
> -
> -/* Helper function that reallocates the EXPOUT inside PS in order to
> - eliminate any unused space. It is generally used when the expression
> - has just been parsed and created. */
> -
> -extern void reallocate_expout (struct parser_state *ps);
> -
> /* Reverse an expression from suffix form (in which it is constructed)
> to prefix form (in which we can conveniently print or execute it).
> Ordinarily this always returns -1. However, if EXPOUT_LAST_STRUCT
> diff --git a/gdb/rust-exp.y b/gdb/rust-exp.y
> index e372a6ea1e..8f1455bbf0 100644
> --- a/gdb/rust-exp.y
> +++ b/gdb/rust-exp.y
> @@ -2670,8 +2670,7 @@ rust_lex_tests (void)
> &test_obstack);
>
> // Set up dummy "parser", so that rust_type works.
> - struct parser_state ps;
> - initialize_expout (&ps, 0, &rust_language_defn, target_gdbarch ());
> + struct parser_state ps (0, &rust_language_defn, target_gdbarch ());
> rust_parser parser (&ps);
>
> rust_lex_test_one ("", 0);
> diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
> index 9f4e00845a..d8a67c750a 100644
> --- a/gdb/stap-probe.c
> +++ b/gdb/stap-probe.c
> @@ -1146,25 +1146,17 @@ static expression_up
> stap_parse_argument (const char **arg, struct type *atype,
> struct gdbarch *gdbarch)
> {
> - struct stap_parse_info p;
> - struct cleanup *back_to;
> -
> /* We need to initialize the expression buffer, in order to begin
> our parsing efforts. We use language_c here because we may need
> to do pointer arithmetics. */
> - initialize_expout (&p.pstate, 10, language_def (language_c), gdbarch);
> - back_to = make_cleanup (free_current_contents, &p.pstate.expout);
> + struct stap_parse_info p (10, language_def (language_c), gdbarch);
>
> p.saved_arg = *arg;
> p.arg = *arg;
> p.arg_type = atype;
> - p.gdbarch = gdbarch;
> - p.inside_paren_p = 0;
>
> stap_parse_argument_1 (&p, 0, STAP_OPERAND_PREC_NONE);
>
> - discard_cleanups (back_to);
> -
> gdb_assert (p.inside_paren_p == 0);
>
> /* Casting the final expression to the appropriate type. */
> @@ -1172,13 +1164,10 @@ stap_parse_argument (const char **arg, struct type *atype,
> write_exp_elt_type (&p.pstate, atype);
> write_exp_elt_opcode (&p.pstate, UNOP_CAST);
>
> - reallocate_expout (&p.pstate);
> -
> p.arg = skip_spaces (p.arg);
> *arg = p.arg;
>
> - /* We can safely return EXPOUT here. */
> - return expression_up (p.pstate.expout);
> + return p.pstate.release ();
> }
>
> /* Implementation of 'parse_arguments' method. */
> diff --git a/gdb/stap-probe.h b/gdb/stap-probe.h
> index c3327e6999..af24a380e0 100644
> --- a/gdb/stap-probe.h
> +++ b/gdb/stap-probe.h
> @@ -28,6 +28,23 @@
>
> struct stap_parse_info
> {
> + /* Constructor. Arguments are passed to the parser_state
> + constructor. */
> + stap_parse_info (size_t initial_size, const struct language_defn *lang,
> + struct gdbarch *gdbarch)
> + : arg (nullptr),
> + pstate (initial_size, lang, gdbarch),
> + saved_arg (nullptr),
> + arg_type (nullptr),
> + gdbarch (gdbarch),
> + inside_paren_p (0)
> + {
> + }
> +
> + ~stap_parse_info () = default;
> +
> + DISABLE_COPY_AND_ASSIGN (stap_parse_info);
> +
> /* The probe's argument in a string format. */
> const char *arg;
>
> --
> 2.13.6
--
Sergio
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