[PATCH 122/203] Introduce var_value_operation

Tom Tromey
2021-01-01T21:48:57Z

This adds class var_value_operation, which implements OP_VAR_VALUE.

gdb/ChangeLog
2021-01-01 Tom Tromey <tom@tromey.com>

* expop.h (class var_value_operation): New.
* eval.c (var_value_operation::evaluate)
(var_value_operation::evaluate_for_address)
(var_value_operation::evaluate_with_coercion)
(var_value_operation::evaluate_for_sizeof)
(var_value_operation::evaluate_for_cast): New methods.
* ax-gdb.c (var_value_operation::do_generate_ax): New method.
---
gdb/ChangeLog | 10 +++++
gdb/ax-gdb.c | 20 +++++++++
gdb/eval.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++
gdb/expop.h | 45 +++++++++++++++++++++
4 files changed, 185 insertions(+)

diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index e0970e87d68..bdf4a6dc39a 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2673,6 +2673,26 @@ unop_cast_type_operation::do_generate_ax (struct expression *exp,
std::get<1> (m_storage)->generate_ax (exp, ax, value, value_type (val));
}

+void
+var_value_operation::do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+{
+ gen_var_ref (ax, value, std::get<0> (m_storage));
+
+ if (value->optimized_out)
+ error (_("`%s' has been optimized out, cannot use"),
+ std::get<0> (m_storage)->print_name ());
+
+ if (value->type->code () == TYPE_CODE_ERROR)
+ {
+ if (cast_type == nullptr)
+ error_unknown_type (std::get<0> (m_storage)->print_name ());
+ value->type = cast_type;
+ }
+}
+
}

/* This handles the middle-to-right-side of code generation for binary
diff --git a/gdb/eval.c b/gdb/eval.c
index 51a737ac5a5..4b12875f00c 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -683,6 +683,23 @@ evaluate_var_value (enum noside noside, const block *blk, symbol *var)
return ret;
}

+namespace expr
+
+{
+
+value *
+var_value_operation::evaluate (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside)
+{
+ symbol *var = std::get<0> (m_storage);
+ if (SYMBOL_TYPE (var)->code () == TYPE_CODE_ERROR)
+ error_unknown_type (var->print_name ());
+ return evaluate_var_value (noside, std::get<1> (m_storage), var);
+}
+
+} /* namespace expr */
+
/* Helper for evaluating an OP_VAR_MSYM_VALUE. */

value *
@@ -3392,6 +3409,54 @@ evaluate_subexp_with_coercion (struct expression *exp,
}
}

+namespace expr
+{
+
+value *
+var_value_operation::evaluate_for_address (struct expression *exp,
+ enum noside noside)
+{
+ symbol *var = std::get<0> (m_storage);
+
+ /* C++: The "address" of a reference should yield the address
+ * of the object pointed to. Let value_addr() deal with it. */
+ if (TYPE_IS_REFERENCE (SYMBOL_TYPE (var)))
+ return operation::evaluate_for_address (exp, noside);
+
+ if (noside == EVAL_AVOID_SIDE_EFFECTS)
+ {
+ struct type *type = lookup_pointer_type (SYMBOL_TYPE (var));
+ enum address_class sym_class = SYMBOL_CLASS (var);
+
+ if (sym_class == LOC_CONST
+ || sym_class == LOC_CONST_BYTES
+ || sym_class == LOC_REGISTER)
+ error (_("Attempt to take address of register or constant."));
+
+ return value_zero (type, not_lval);
+ }
+ else
+ return address_of_variable (var, std::get<1> (m_storage));
+}
+
+value *
+var_value_operation::evaluate_with_coercion (struct expression *exp,
+ enum noside noside)
+{
+ struct symbol *var = std::get<0> (m_storage);
+ struct type *type = check_typedef (SYMBOL_TYPE (var));
+ if (type->code () == TYPE_CODE_ARRAY
+ && !type->is_vector ()
+ && CAST_IS_CONVERSION (exp->language_defn))
+ {
+ struct value *val = address_of_variable (var, std::get<1> (m_storage));
+ return value_cast (lookup_pointer_type (TYPE_TARGET_TYPE (type)), val);
+ }
+ return evaluate (nullptr, exp, noside);
+}
+
+}
+
/* Helper function for evaluating the size of a type. */

static value *
@@ -3632,6 +3697,27 @@ unop_memval_type_operation::evaluate_for_sizeof (struct expression *exp,
return evaluate_subexp_for_sizeof_base (exp, value_type (typeval));
}

+value *
+var_value_operation::evaluate_for_sizeof (struct expression *exp,
+ enum noside noside)
+{
+ struct type *type = SYMBOL_TYPE (std::get<0> (m_storage));
+ if (is_dynamic_type (type))
+ {
+ value *val = evaluate (nullptr, exp, EVAL_NORMAL);
+ type = value_type (val);
+ if (type->code () == TYPE_CODE_ARRAY
+ && is_dynamic_type (type->index_type ())
+ && type->bounds ()->high.kind () == PROP_UNDEFINED)
+ {
+ /* FIXME: This should be size_t. */
+ struct type *size_type = builtin_type (exp->gdbarch)->builtin_int;
+ return allocate_optimized_out_value (size_type);
+ }
+ }
+ return evaluate_subexp_for_sizeof_base (exp, type);
+}
+
}

/* Evaluate a subexpression of EXP, at index *POS, and return a value
@@ -3719,6 +3805,30 @@ var_msym_value_operation::evaluate_for_cast (struct type *to_type,
return val;
}

+value *
+var_value_operation::evaluate_for_cast (struct type *to_type,
+ struct expression *exp,
+ enum noside noside)
+{
+ value *val = evaluate_var_value (noside,
+ std::get<1> (m_storage),
+ std::get<0> (m_storage));
+
+ if (noside == EVAL_SKIP)
+ return eval_skip_value (exp);
+
+ val = value_cast (to_type, val);
+
+ /* Don't allow e.g. '&(int)var_with_no_debug_info'. */
+ if (VALUE_LVAL (val) == lval_memory)
+ {
+ if (value_lazy (val))
+ value_fetch_lazy (val);
+ VALUE_LVAL (val) = not_lval;
+ }
+ return val;
+}
+
}

/* Parse a type expression in the string [P..P+LENGTH). */
diff --git a/gdb/expop.h b/gdb/expop.h
index 53ff93c4b83..0c489c77450 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -606,6 +606,51 @@ class scope_operation
override;
};

+/* Compute the value of a variable. */
+class var_value_operation
+ : public tuple_holding_operation<symbol *, const block *>
+{
+public:
+
+ using tuple_holding_operation::tuple_holding_operation;
+
+ value *evaluate (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override;
+
+ value *evaluate_with_coercion (struct expression *exp,
+ enum noside noside) override;
+
+ value *evaluate_for_sizeof (struct expression *exp, enum noside noside)
+ override;
+
+ value *evaluate_for_cast (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override;
+
+ value *evaluate_for_address (struct expression *exp, enum noside noside)
+ override;
+
+ enum exp_opcode opcode () const override
+ { return OP_VAR_VALUE; }
+
+ bool constant_p () const override
+ {
+ symbol *sym = std::get<0> (m_storage);
+ return (SYMBOL_CLASS (sym) == LOC_CONST
+ || SYMBOL_CLASS (sym) == LOC_CONST_BYTES
+ || SYMBOL_CLASS (sym) == LOC_LABEL);
+ }
+
+protected:
+
+ void do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+ override;
+};
+
class long_const_operation
: public tuple_holding_operation<struct type *, LONGEST>
{
--
2.26.2