[1/3] gdb: store internalvars in an std::vector
Commit Message
Change the storage of internalvars to an std::vector of unique pointers
to internalval. This helps automate memory management, and will help
keep internalvars sorted in a subsequent patch.
I initially tried to use an std::vector<internalval> initially, but some
parts of the code need for the addresses of internalvars to be stable.
Change-Id: I1fca7e7877cc984a3a3432c7639d45e68d437241
---
gdb/value.c | 32 +++++++++++++-------------------
1 file changed, 13 insertions(+), 19 deletions(-)
Comments
On Mon, Feb 13, 2023 at 11:21:37PM -0500, Simon Marchi via Gdb-patches wrote:
> Change the storage of internalvars to an std::vector of unique pointers
> to internalval. This helps automate memory management, and will help
> keep internalvars sorted in a subsequent patch.
>
> I initially tried to use an std::vector<internalval> initially, but some
> parts of the code need for the addresses of internalvars to be stable.
>
Hi Simon,
As the end-goal is to have an order, did you consider using a container
which enforces it like a std::map? For small number of objects (for
some definition of small…) vector is usually more efficient but as here
you hold pointers, I am not sure the vector brings a huge benefit.
You could use a std::map<std::string, internalvar> as the internalvar’s
address will remain stable. No need to have a unique_ptr.
One downside of the std::map is that you might end up with the name
stored twice (once as key, and maybe still once in the internalvar
object). std::set can also be used, but with other downsides.
The main difference with vector can come if we had 2 internal variables
with the same name. The current code does not prevent this AFAICT, but
as one of the vars would effectively shadow the other, I am not sure
this is a case we want to support anyway.
Best,
Lancelot.
> Change-Id: I1fca7e7877cc984a3a3432c7639d45e68d437241
> ---
> gdb/value.c | 32 +++++++++++++-------------------
> 1 file changed, 13 insertions(+), 19 deletions(-)
>
> diff --git a/gdb/value.c b/gdb/value.c
> index 7873aeb9558e..e884913abe5a 100644
> --- a/gdb/value.c
> +++ b/gdb/value.c
> @@ -1829,7 +1829,6 @@ union internalvar_data
>
> struct internalvar
> {
> - struct internalvar *next;
> char *name;
>
> /* We support various different kinds of content of an internal variable.
> @@ -1841,7 +1840,9 @@ struct internalvar
> union internalvar_data u;
> };
>
> -static struct internalvar *internalvars;
> +using internalvar_up = std::unique_ptr<internalvar>;
> +
> +static std::vector<internalvar_up> internalvars;
>
> /* If the variable does not already exist create it and give it the
> value given. If no value is given then the default is zero. */
> @@ -1891,11 +1892,9 @@ init_if_undefined_command (const char* args, int from_tty)
> struct internalvar *
> lookup_only_internalvar (const char *name)
> {
> - struct internalvar *var;
> -
> - for (var = internalvars; var; var = var->next)
> + for (internalvar_up &var : internalvars)
> if (strcmp (var->name, name) == 0)
> - return var;
> + return var.get ();
>
> return NULL;
> }
> @@ -1906,12 +1905,11 @@ lookup_only_internalvar (const char *name)
> void
> complete_internalvar (completion_tracker &tracker, const char *name)
> {
> - struct internalvar *var;
> int len;
>
> len = strlen (name);
>
> - for (var = internalvars; var; var = var->next)
> + for (internalvar_up &var : internalvars)
> if (strncmp (var->name, name, len) == 0)
> tracker.add_completion (make_unique_xstrdup (var->name));
> }
> @@ -1922,12 +1920,12 @@ complete_internalvar (completion_tracker &tracker, const char *name)
> struct internalvar *
> create_internalvar (const char *name)
> {
> - struct internalvar *var = XNEW (struct internalvar);
> + internalvars.emplace_back (new internalvar);
> + internalvar *var = internalvars.back ().get ();
>
> var->name = xstrdup (name);
> var->kind = INTERNALVAR_VOID;
> - var->next = internalvars;
> - internalvars = var;
> +
> return var;
> }
>
> @@ -2412,8 +2410,6 @@ preserve_one_varobj (struct varobj *varobj, struct objfile *objfile,
> void
> preserve_values (struct objfile *objfile)
> {
> - struct internalvar *var;
> -
> /* Create the hash table. We allocate on the objfile's obstack, since
> it is soon to be deleted. */
> htab_up copied_types = create_copied_types_hash ();
> @@ -2421,8 +2417,8 @@ preserve_values (struct objfile *objfile)
> for (const value_ref_ptr &item : value_history)
> item->preserve (objfile, copied_types.get ());
>
> - for (var = internalvars; var; var = var->next)
> - preserve_one_internalvar (var, objfile, copied_types.get ());
> + for (internalvar_up &var : internalvars)
> + preserve_one_internalvar (var.get (), objfile, copied_types.get ());
>
> /* For the remaining varobj, check that none has type owned by OBJFILE. */
> all_root_varobjs ([&copied_types, objfile] (struct varobj *varobj)
> @@ -2438,14 +2434,12 @@ static void
> show_convenience (const char *ignore, int from_tty)
> {
> struct gdbarch *gdbarch = get_current_arch ();
> - struct internalvar *var;
> int varseen = 0;
> struct value_print_options opts;
>
> get_user_print_options (&opts);
> - for (var = internalvars; var; var = var->next)
> + for (internalvar_up &var : internalvars)
> {
> -
> if (!varseen)
> {
> varseen = 1;
> @@ -2456,7 +2450,7 @@ show_convenience (const char *ignore, int from_tty)
> {
> struct value *val;
>
> - val = value_of_internalvar (gdbarch, var);
> + val = value_of_internalvar (gdbarch, var.get ());
> value_print (val, gdb_stdout, &opts);
> }
> catch (const gdb_exception_error &ex)
> --
> 2.39.1
>
On 2/14/23 05:54, Lancelot SIX via Gdb-patches wrote:
> On Mon, Feb 13, 2023 at 11:21:37PM -0500, Simon Marchi via Gdb-patches wrote:
>> Change the storage of internalvars to an std::vector of unique pointers
>> to internalval. This helps automate memory management, and will help
>> keep internalvars sorted in a subsequent patch.
>>
>> I initially tried to use an std::vector<internalval> initially, but some
>> parts of the code need for the addresses of internalvars to be stable.
>>
>
> Hi Simon,
>
> As the end-goal is to have an order, did you consider using a container
> which enforces it like a std::map? For small number of objects (for
> some definition of small…) vector is usually more efficient but as here
> you hold pointers, I am not sure the vector brings a huge benefit.
>
> You could use a std::map<std::string, internalvar> as the internalvar’s
> address will remain stable. No need to have a unique_ptr.
>
> One downside of the std::map is that you might end up with the name
> stored twice (once as key, and maybe still once in the internalvar
> object). std::set can also be used, but with other downsides.
I had not thought of that, but I think it's a good idea. Having the
name stored twice is not an issue, I think.
> The main difference with vector can come if we had 2 internal variables
> with the same name. The current code does not prevent this AFAICT, but
> as one of the vars would effectively shadow the other, I am not sure
> this is a case we want to support anyway.
I don't think it can really happen today anyway.
create_internalvar_type_lazy is only used to create variable known in
advance, for which we know there are no clashes. And through
lookup_internalvar, create_internalvar is only called after seeing that
there is no variable by that name. So, I think we'll be fine with a
map.
Simon
@@ -1829,7 +1829,6 @@ union internalvar_data
struct internalvar
{
- struct internalvar *next;
char *name;
/* We support various different kinds of content of an internal variable.
@@ -1841,7 +1840,9 @@ struct internalvar
union internalvar_data u;
};
-static struct internalvar *internalvars;
+using internalvar_up = std::unique_ptr<internalvar>;
+
+static std::vector<internalvar_up> internalvars;
/* If the variable does not already exist create it and give it the
value given. If no value is given then the default is zero. */
@@ -1891,11 +1892,9 @@ init_if_undefined_command (const char* args, int from_tty)
struct internalvar *
lookup_only_internalvar (const char *name)
{
- struct internalvar *var;
-
- for (var = internalvars; var; var = var->next)
+ for (internalvar_up &var : internalvars)
if (strcmp (var->name, name) == 0)
- return var;
+ return var.get ();
return NULL;
}
@@ -1906,12 +1905,11 @@ lookup_only_internalvar (const char *name)
void
complete_internalvar (completion_tracker &tracker, const char *name)
{
- struct internalvar *var;
int len;
len = strlen (name);
- for (var = internalvars; var; var = var->next)
+ for (internalvar_up &var : internalvars)
if (strncmp (var->name, name, len) == 0)
tracker.add_completion (make_unique_xstrdup (var->name));
}
@@ -1922,12 +1920,12 @@ complete_internalvar (completion_tracker &tracker, const char *name)
struct internalvar *
create_internalvar (const char *name)
{
- struct internalvar *var = XNEW (struct internalvar);
+ internalvars.emplace_back (new internalvar);
+ internalvar *var = internalvars.back ().get ();
var->name = xstrdup (name);
var->kind = INTERNALVAR_VOID;
- var->next = internalvars;
- internalvars = var;
+
return var;
}
@@ -2412,8 +2410,6 @@ preserve_one_varobj (struct varobj *varobj, struct objfile *objfile,
void
preserve_values (struct objfile *objfile)
{
- struct internalvar *var;
-
/* Create the hash table. We allocate on the objfile's obstack, since
it is soon to be deleted. */
htab_up copied_types = create_copied_types_hash ();
@@ -2421,8 +2417,8 @@ preserve_values (struct objfile *objfile)
for (const value_ref_ptr &item : value_history)
item->preserve (objfile, copied_types.get ());
- for (var = internalvars; var; var = var->next)
- preserve_one_internalvar (var, objfile, copied_types.get ());
+ for (internalvar_up &var : internalvars)
+ preserve_one_internalvar (var.get (), objfile, copied_types.get ());
/* For the remaining varobj, check that none has type owned by OBJFILE. */
all_root_varobjs ([&copied_types, objfile] (struct varobj *varobj)
@@ -2438,14 +2434,12 @@ static void
show_convenience (const char *ignore, int from_tty)
{
struct gdbarch *gdbarch = get_current_arch ();
- struct internalvar *var;
int varseen = 0;
struct value_print_options opts;
get_user_print_options (&opts);
- for (var = internalvars; var; var = var->next)
+ for (internalvar_up &var : internalvars)
{
-
if (!varseen)
{
varseen = 1;
@@ -2456,7 +2450,7 @@ show_convenience (const char *ignore, int from_tty)
{
struct value *val;
- val = value_of_internalvar (gdbarch, var);
+ val = value_of_internalvar (gdbarch, var.get ());
value_print (val, gdb_stdout, &opts);
}
catch (const gdb_exception_error &ex)