Component bslstl_errc [Package bslstl]

Provide a standard compliant version of errc. More...

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Descriptive System Error Value Names

Purpose:

Provide a standard compliant version of errc.

Classes:

bsl::errc	namespace for errc enumeration type
bsl::ErrcEnum	typedef for bsl::errc::Enum or std::errc

Canonical Header:

bsl_system_error.h

Description:

This component defines an enumeration bsl::errc::Enum, and marks it eligible to participate as an error condition in 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 the type alias bsl::ErrcEnum that can be used as the type of the errc enumeration in both C++03 and C++11 mode. Because errc is defined in C++11 as an enum class, we cannot emulate use of std::errc in C++03 mode - that tag can either be used to qualify the enumeration literals or name the type, but not both. This component chooses to have bsl::errc be the literal qualifier and bsl::ErrcEnum be the type so to use this component portably, one would, for example, write

  bsl::ErrcEnum error_value = bsl::errc::io_error;

Usage:

In this section we show intended use of this component.

Example 1: Descriptive System Error Value Names:

Suppose we would like to have more descriptive and non-macro names for errno system error values. We can use the errc from the system_error facility of the C++ standard for this.

First, we do something that will set an error value.

  strtod("1e2000", 0);

Finally, we check for that error using the descriptive name.

  bsl::ErrcEnum expected = bsl::errc::result_out_of_range;
  assert(static_cast<int>(expected) == errno);