[PATCH 112/203] Introduce unop_sizeof_operation

Tom Tromey
2021-01-01T21:48:50Z

This adds class unop_sizeof_operation, which implements UNOP_SIZEOF.

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

* expop.h (class unop_sizeof_operation): New.
* ax-gdb.c (unop_sizeof_operation::do_generate_ax): New method.
---
gdb/ChangeLog | 5 +++++
gdb/ax-gdb.c | 23 +++++++++++++++++++++++
gdb/expop.h | 29 +++++++++++++++++++++++++++++
3 files changed, 57 insertions(+)

diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 64710887534..756f4d7969a 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2491,6 +2491,29 @@ comma_operation::do_generate_ax (struct expression *exp,
/* It's the consumer's responsibility to trace the right operand. */
}

+void
+unop_sizeof_operation::do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+{
+ /* We don't care about the value of the operand expression; we only
+ care about its type. However, in the current arrangement, the
+ only way to find an expression's type is to generate code for it.
+ So we generate code for the operand, and then throw it away,
+ replacing it with code that simply pushes its size. */
+ int start = ax->len;
+
+ std::get<0> (m_storage)->generate_ax (exp, ax, value);
+
+ /* Throw away the code we just generated. */
+ ax->len = start;
+
+ ax_const_l (ax, TYPE_LENGTH (value->type));
+ value->kind = axs_rvalue;
+ value->type = builtin_type (ax->gdbarch)->builtin_int;
+}
+
}

/* This handles the middle-to-right-side of code generation for binary
diff --git a/gdb/expop.h b/gdb/expop.h
index 8ddc26d329a..22af0c824e2 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -1571,6 +1571,35 @@ class unop_addr_operation
}
};

+/* Implement 'sizeof'. */
+class unop_sizeof_operation
+ : public maybe_constant_operation<operation_up>
+{
+public:
+
+ using maybe_constant_operation::maybe_constant_operation;
+
+ value *evaluate (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override
+ {
+ if (noside == EVAL_SKIP)
+ return eval_skip_value (exp);
+ return std::get<0> (m_storage)->evaluate_for_sizeof (exp, noside);
+ }
+
+ enum exp_opcode opcode () const override
+ { return UNOP_SIZEOF; }
+
+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