bslstl_iserrorconditionenum

Macros
#define	BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE   std

Detailed Description

Outline

• Purpose
• Classes
• Macros
• Description
  • Usage
    • Example 1: Dedicated Error Values

Purpose

Provide a compliant standard is_error_condition_enum trait.

Classes

• bsl::is_error_condition_enum: standard complaint is_error_condition_enum

Macros

• BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE: namespace to specialize the triat

Canonical header: bsl_system_error.h

Description

This component defines a class template, bsl::is_error_condition_enum, intended to be specialized for enumeration types that are designated as error conditions for the <system_error> facility. In C++11 mode, the vendor-supplied <system_error> implementation is used instead, and the corresponding names from std are imported into bsl. This component also defines a macro, BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE, to be used as the namespace in which to write specializations of is_error_condition_enum.

Usage

In this section we show intended use of this component.

Example 1: Dedicated Error Values

Suppose we have a dedicated system with a set of possible errors, and we want to be able to throw descriptive exceptions when an error occurs. We need to work with the <system_error> facility to support this, starting by marking the enumeration type that defines the error literals as eligible to participate. We can use bsl::is_error_condition to do this.

First, we define the set of error values for our system.

struct CarError {
    // TYPES
    enum Enum {
        k_CAR_WHEELS_CAME_OFF = 1,
        k_CAR_ENGINE_FELL_OUT = 2
    };
};

Then, we enable the trait marking this as an error condition.

namespace BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE {
template <> struct is_error_condition_enum<CarError::Enum>
: public true_type { };
}  // close namespace BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE

Finally, we verify that the trait marks our type as eligible.

assert(is_error_condition_enum<CarError::Enum>::value);

Macro Definition Documentation

BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE

#define BSL_IS_ERROR_CONDITION_ENUM_NAMESPACE   std