gdb: Setting setter return a bool to tell if the value changed
GDB can notify observers when a parameter is changed.
To do that, do_set_command (in gdb/cli/cli-setshow.c) compares the new
value against the old one before updating it, and based on that notifies
observers. This looks like something like:
int valuechanged = 0;
switch (cmd->var.type ())
{
case var_integer:
{
LONGEST new_val = parse_and_eval_long (arg)
if (new_val != cmd->var.get<int> ())
{
cmd->var.get<int> (new_val);
value_changes = 1;
}
}
break;
case var_string:
{
std::string val = std::string (arg);
if (new_val != cmd->var.get<std::string> ())
{
cmd->var.get<std::string> (new_val);
value_changes = 1;
}
}
break;
case...
/* And so on for all possible var_types. */
}
This comparison is done for each possible var_type, which leads to
unnecessary code duplication.
In this patch I propose to move all those checks in one place within the
setting setter method. This limits the code duplication and simplifies
the do_set_command implementation.
This patch also changes slightly the way a value change is detected.
Instead of comparing the user provided value against the current value
of the setting, we compare the value of the setting before and after the
set operation. This is meant to handle edge cases where trying to set
an unrecognized value would be equivalent to a noop (the actual value
remains unchanged).
There should be no user visible change introduced by this commit.
Tested on x86_64 GNU/Linux.
[1] https://review.lttng.org/c/binutils-gdb/+/5831/41
Change-Id: If064b9cede3eb56275aacd2b286f74eceb1aed11
diff --git a/gdb/cli/cli-setshow.c b/gdb/cli/cli-setshow.c
index 0f87b92..f06c927 100644
--- a/gdb/cli/cli-setshow.c
+++ b/gdb/cli/cli-setshow.c
@@ -360,26 +360,12 @@
*q++ = '\0';
newobj = (char *) xrealloc (newobj, q - newobj);
- const std::string cur_val = c->var->get<std::string> ();
- if (cur_val != std::string (newobj))
- {
- c->var->set<std::string> (std::string (newobj));
-
- option_changed = true;
- }
+ option_changed = c->var->set<std::string> (std::string (newobj));
xfree (newobj);
}
break;
case var_string_noescape:
- {
- const std::string cur_val = c->var->get<std::string> ();
- if (cur_val != arg)
- {
- c->var->set<std::string> (std::string (arg));
-
- option_changed = true;
- }
- }
+ option_changed = c->var->set<std::string> (std::string (arg));
break;
case var_filename:
if (*arg == '\0')
@@ -405,13 +391,8 @@
else
val = xstrdup ("");
- const std::string cur_val = c->var->get<std::string> ();
- if (cur_val != std::string (val))
- {
- c->var->set<std::string> (std::string (val));
-
- option_changed = true;
- }
+ option_changed
+ = c->var->set<std::string> (std::string (val));
xfree (val);
}
break;
@@ -421,39 +402,18 @@
if (val < 0)
error (_("\"on\" or \"off\" expected."));
- if (val != c->var->get<bool> ())
- {
- c->var->set<bool> (val);
- option_changed = true;
- }
+ option_changed = c->var->set<bool> (val);
}
break;
case var_auto_boolean:
- {
- enum auto_boolean val = parse_auto_binary_operation (arg);
-
- if (c->var->get<enum auto_boolean> () != val)
- {
- c->var->set<enum auto_boolean> (val);
-
- option_changed = true;
- }
- }
+ option_changed = c->var->set<enum auto_boolean> (parse_auto_binary_operation (arg));
break;
case var_uinteger:
case var_zuinteger:
- {
- unsigned int val
- = parse_cli_var_uinteger (c->var->type (), &arg, true);
-
- if (c->var->get<unsigned int> () != val)
- {
- c->var->set<unsigned int> (val);
-
- option_changed = true;
- }
- }
+ option_changed
+ = c->var->set<unsigned int> (parse_cli_var_uinteger (c->var->type (),
+ &arg, true));
break;
case var_integer:
case var_zinteger:
@@ -483,12 +443,7 @@
|| (c->var->type () == var_zinteger && val > INT_MAX))
error (_("integer %s out of range"), plongest (val));
- if (c->var->get<int> () != val)
- {
- c->var->set<int> (val);
-
- option_changed = true;
- }
+ option_changed = c->var->set<int> (val);
}
break;
case var_enum:
@@ -501,24 +456,12 @@
if (*after != '\0')
error (_("Junk after item \"%.*s\": %s"), len, arg, after);
- if (c->var->get<const char *> () != match)
- {
- c->var->set<const char *> (match);
-
- option_changed = true;
- }
+ option_changed = c->var->set<const char *> (match);
}
break;
case var_zuinteger_unlimited:
- {
- int val = parse_cli_var_zuinteger_unlimited (&arg, true);
-
- if (c->var->get<int> () != val)
- {
- c->var->set<int> (val);
- option_changed = true;
- }
- }
+ option_changed = c->var->set<int>
+ (parse_cli_var_zuinteger_unlimited (&arg, true));
break;
default:
error (_("gdb internal error: bad var_type in do_setshow_command"));
diff --git a/gdb/command.h b/gdb/command.h
index 1262629..2c21e68 100644
--- a/gdb/command.h
+++ b/gdb/command.h
@@ -286,12 +286,14 @@
The var_type of the setting must match T. */
template<typename T>
- void set (T v)
+ bool set (T v)
{
/* Check that the current instance is of one of the supported types for
this instantiation. */
gdb_assert (var_type_uses<T> (this->m_var_type));
+ const T old_value = this->get<T> ();
+
if (m_setter != nullptr)
{
auto setter = reinterpret_cast<setting_setter_ftype<T>> (m_setter);
@@ -302,6 +304,8 @@
gdb_assert (this->m_var != nullptr);
*static_cast<T *> (this->m_var) = v;
}
+
+ return old_value != this->get<T> ();
}
protected:
