Re: [RFA] Remove a cleanup from parse_expression_for_completion

Tom Tromey
2018-02-20T20:23:27Z

>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:

Tom> There is a case in here where the NULL/empty string distinction matters.
Tom> So I think we can't use std::string but must instead use
Tom> unique_xmalloc_ptr. I'll update the patch.

Here's the new version. Re-tested on the buildbot & I looked more
carefully at the results this time; also I tried all the
completion-related tests locally as well.

Tom

commit 3de98da217150149d26dadee2c0ca9825463adda
Author: Tom Tromey <tom@tromey.com>
Date: Thu Feb 15 22:41:03 2018 -0700

Remove a cleanup from parse_expression_for_completion

This removes a cleanup from parse_expression_for_completion, by
changing various expression-completion functions to use
gdb::unique_xmalloc_ptry rather than explicit malloc+free.

Regression tested by the buildbot.

gdb/ChangeLog
2018-02-19 Tom Tromey <tom@tromey.com>

* value.h: (extract_field_op): Update.
* eval.c (extract_field_op): Return a const char *.
* expression.h (parse_expression_for_completion): Update.
* completer.c (complete_expression): Update.
(add_struct_fields): Make fieldname const.
* parse.c (expout_completion_name): Now a unique_xmalloc_ptr.
(mark_completion_tag, parse_exp_in_context_1): Update.
(parse_expression_for_completion): Change "name" to
unique_xmalloc_ptr*.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index cd8ef6653d..ca660163fa 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2018-02-19 Tom Tromey <tom@tromey.com>
+
+ * value.h: (extract_field_op): Update.
+ * eval.c (extract_field_op): Return a const char *.
+ * expression.h (parse_expression_for_completion): Update.
+ * completer.c (complete_expression): Update.
+ (add_struct_fields): Make fieldname const.
+ * parse.c (expout_completion_name): Now a unique_xmalloc_ptr.
+ (mark_completion_tag, parse_exp_in_context_1): Update.
+ (parse_expression_for_completion): Change "name" to
+ unique_xmalloc_ptr*.
+
2018-02-19 Alan Hayward <alan.hayward@arm.com>

* Makefile.in: (COMMON_SFILES): Add common/*.c files.
diff --git a/gdb/completer.c b/gdb/completer.c
index a71bd368ff..4de1bcff32 100644
--- a/gdb/completer.c
+++ b/gdb/completer.c
@@ -962,7 +962,7 @@ location_completer_handle_brkchars (struct cmd_list_element *ignore,

static void
add_struct_fields (struct type *type, completion_list &output,
- char *fieldname, int namelen)
+ const char *fieldname, int namelen)
{
int i;
int computed_type_name = 0;
@@ -1016,12 +1016,11 @@ complete_expression (completion_tracker &tracker,
const char *text, const char *word)
{
struct type *type = NULL;
- char *fieldname;
+ gdb::unique_xmalloc_ptr<char> fieldname;
enum type_code code = TYPE_CODE_UNDEF;

/* Perform a tentative parse of the expression, to see whether a
field completion is required. */
- fieldname = NULL;
TRY
{
type = parse_expression_for_completion (text, &fieldname, &code);
@@ -1032,7 +1031,7 @@ complete_expression (completion_tracker &tracker,
}
END_CATCH

- if (fieldname && type)
+ if (fieldname != nullptr && type)
{
for (;;)
{
@@ -1045,25 +1044,20 @@ complete_expression (completion_tracker &tracker,
if (TYPE_CODE (type) == TYPE_CODE_UNION
|| TYPE_CODE (type) == TYPE_CODE_STRUCT)
{
- int flen = strlen (fieldname);
completion_list result;

- add_struct_fields (type, result, fieldname, flen);
- xfree (fieldname);
+ add_struct_fields (type, result, fieldname.get (),
+ strlen (fieldname.get ()));
tracker.add_completions (std::move (result));
return;
}
}
- else if (fieldname && code != TYPE_CODE_UNDEF)
+ else if (fieldname != nullptr && code != TYPE_CODE_UNDEF)
{
- struct cleanup *cleanup = make_cleanup (xfree, fieldname);
-
- collect_symbol_completion_matches_type (tracker, fieldname, fieldname,
- code);
- do_cleanups (cleanup);
+ collect_symbol_completion_matches_type (tracker, fieldname.get (),
+ fieldname.get (), code);
return;
}
- xfree (fieldname);

complete_files_symbols (tracker, text, word);
}
diff --git a/gdb/eval.c b/gdb/eval.c
index 6f74c41b9f..4899011a58 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -272,7 +272,7 @@ fetch_subexp_value (struct expression *exp, int *pc, struct value **valp,
subexpression of the left-hand-side of the dereference. This is
used when completing field names. */

-char *
+const char *
extract_field_op (struct expression *exp, int *subexp)
{
int tem;
diff --git a/gdb/expression.h b/gdb/expression.h
index 030f2f08e7..59a0898805 100644
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -101,7 +101,8 @@ extern expression_up parse_expression (const char *);
extern expression_up parse_expression_with_language (const char *string,
enum language lang);

-extern struct type *parse_expression_for_completion (const char *, char **,
+extern struct type *parse_expression_for_completion (const char *,
+ gdb::unique_xmalloc_ptr<char> *,
enum type_code *);

extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
diff --git a/gdb/parse.c b/gdb/parse.c
index e3f1306a17..3abb9d4219 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -88,7 +88,7 @@ static int expout_last_struct = -1;
static enum type_code expout_tag_completion_type = TYPE_CODE_UNDEF;

/* The token for tagged type name completion. */
-static char *expout_completion_name;
+static gdb::unique_xmalloc_ptr<char> expout_completion_name;

\f
static unsigned int expressiondebug = 0;
@@ -575,9 +575,7 @@ mark_completion_tag (enum type_code tag, const char *ptr, int length)
|| tag == TYPE_CODE_STRUCT
|| tag == TYPE_CODE_ENUM);
expout_tag_completion_type = tag;
- expout_completion_name = (char *) xmalloc (length + 1);
- memcpy (expout_completion_name, ptr, length);
- expout_completion_name[length] = '\0';
+ expout_completion_name.reset (xstrndup (ptr, length));
}

\f
@@ -1137,8 +1135,7 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
type_stack.depth = 0;
expout_last_struct = -1;
expout_tag_completion_type = TYPE_CODE_UNDEF;
- xfree (expout_completion_name);
- expout_completion_name = NULL;
+ expout_completion_name.reset ();

comma_terminates = comma;

@@ -1277,11 +1274,11 @@ parse_expression_with_language (const char *string, enum language lang)
reference; furthermore, if the parsing ends in the field name,
return the field name in *NAME. If the parsing ends in the middle
of a field reference, but the reference is somehow invalid, throw
- an exception. In all other cases, return NULL. Returned non-NULL
- *NAME must be freed by the caller. */
+ an exception. In all other cases, return NULL. */

struct type *
-parse_expression_for_completion (const char *string, char **name,
+parse_expression_for_completion (const char *string,
+ gdb::unique_xmalloc_ptr<char> *name,
enum type_code *code)
{
expression_up exp;
@@ -1306,23 +1303,24 @@ parse_expression_for_completion (const char *string, char **name,
if (expout_tag_completion_type != TYPE_CODE_UNDEF)
{
*code = expout_tag_completion_type;
- *name = expout_completion_name;
- expout_completion_name = NULL;
+ *name = std::move (expout_completion_name);
return NULL;
}

if (expout_last_struct == -1)
return NULL;

- *name = extract_field_op (exp.get (), &subexp);
- if (!*name)
- return NULL;
+ const char *fieldname = extract_field_op (exp.get (), &subexp);
+ if (fieldname == NULL)
+ {
+ name->reset ();
+ return NULL;
+ }

+ name->reset (xstrdup (fieldname));