[PATCH 079/203] Introduce var_msym_value_operation

Tom Tromey
2021-01-01T21:48:22Z

This adds class var_msym_value_operation, which implements
OP_VAR_MSYM_VALUE.

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

* expop.h (class var_msym_value_operation): New.
* eval.c (eval_op_var_msym_value): No longer static.
(var_msym_value_operation::evaluate_for_address)
(var_msym_value_operation::evaluate_for_sizeof)
(var_msym_value_operation::evaluate_for_cast): New methods.
* ax-gdb.c (var_msym_value_operation::do_generate_ax): New
method.
---
gdb/ChangeLog | 10 ++++++++
gdb/ax-gdb.c | 17 +++++++++++++
gdb/eval.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++-
gdb/expop.h | 43 ++++++++++++++++++++++++++++++++
4 files changed, 138 insertions(+), 1 deletion(-)

diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 7640b1ba925..60281700703 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2324,6 +2324,23 @@ long_const_operation::do_generate_ax (struct expression *exp,
std::get<0> (m_storage));
}

+void
+var_msym_value_operation::do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+{
+ gen_msym_var_ref (ax, value, std::get<0> (m_storage),
+ std::get<1> (m_storage));
+
+ if (value->type->code () == TYPE_CODE_ERROR)
+ {
+ if (cast_type == nullptr)
+ error_unknown_type (std::get<0> (m_storage)->linkage_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 fe8698342db..38bbb3519ba 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -1216,7 +1216,7 @@ eval_op_var_entry_value (struct type *expect_type, struct expression *exp,
return SYMBOL_COMPUTED_OPS (sym)->read_variable_at_entry (sym, frame);
}

-static struct value *
+struct value *
eval_op_var_msym_value (struct type *expect_type, struct expression *exp,
enum noside noside,
minimal_symbol *msymbol, struct objfile *objfile)
@@ -3276,6 +3276,22 @@ scope_operation::evaluate_for_address (struct expression *exp,
return x;
}

+value *
+var_msym_value_operation::evaluate_for_address (struct expression *exp,
+ enum noside noside)
+{
+ value *val = evaluate_var_msym_value (noside,
+ std::get<1> (m_storage),
+ std::get<0> (m_storage));
+ if (noside == EVAL_AVOID_SIDE_EFFECTS)
+ {
+ struct type *type = lookup_pointer_type (value_type (val));
+ return value_zero (type, not_lval);
+ }
+ else
+ return value_addr (val);
+}
+
}

/* Evaluate like `evaluate_subexp' except coercing arrays to pointers.
@@ -3476,6 +3492,25 @@ operation::evaluate_for_sizeof (struct expression *exp, enum noside noside)
return evaluate_subexp_for_sizeof_base (exp, value_type (val));
}

+value *
+var_msym_value_operation::evaluate_for_sizeof (struct expression *exp,
+ enum noside noside)
+
+{
+ minimal_symbol *msymbol = std::get<0> (m_storage);
+ value *mval = evaluate_var_msym_value (noside,
+ std::get<1> (m_storage),
+ msymbol);
+
+ struct type *type = value_type (mval);
+ if (type->code () == TYPE_CODE_ERROR)
+ error_unknown_type (msymbol->print_name ());
+
+ /* FIXME: This should be size_t. */
+ struct type *size_type = builtin_type (exp->gdbarch)->builtin_int;
+ return value_from_longest (size_type, TYPE_LENGTH (type));
+}
+
}

/* Evaluate a subexpression of EXP, at index *POS, and return a value
@@ -3533,6 +3568,38 @@ evaluate_subexp_for_cast (expression *exp, int *pos,
return value_cast (to_type, val);
}

+namespace expr
+{
+
+value *
+var_msym_value_operation::evaluate_for_cast (struct type *to_type,
+ struct expression *exp,
+ enum noside noside)
+{
+ if (noside == EVAL_AVOID_SIDE_EFFECTS)
+ return value_zero (to_type, not_lval);
+
+ value *val = evaluate_var_msym_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). */

struct type *
diff --git a/gdb/expop.h b/gdb/expop.h
index ede075b44d8..caa4d329fef 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -45,6 +45,11 @@ extern struct value *eval_op_scope (struct type *expect_type,
struct expression *exp,
enum noside noside,
struct type *type, const char *string);
+extern struct value *eval_op_var_msym_value (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside,
+ minimal_symbol *msymbol,
+ struct objfile *objfile);

namespace expr
{
@@ -479,6 +484,44 @@ class long_const_operation
override;
};

+class var_msym_value_operation
+ : public maybe_constant_operation<minimal_symbol *, struct objfile *>
+{
+public:
+
+ using maybe_constant_operation::maybe_constant_operation;
+
+ value *evaluate (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override
+ {
+ return eval_op_var_msym_value (expect_type, exp, noside,
+ std::get<0> (m_storage),
+ std::get<1> (m_storage));
+ }
+
+ value *evaluate_for_sizeof (struct expression *exp, enum noside noside)
+ override;
+
+ value *evaluate_for_address (struct expression *exp, enum noside noside)
+ override;
+
+ value *evaluate_for_cast (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override;
+
+ enum exp_opcode opcode () const override
+ { return OP_VAR_MSYM_VALUE; }
+
+protected:
+
+ void do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+ override;
+};
+
} /* namespace expr */

#endif /* EXPOP_H */
--
2.26.2