bslstl_systemerror

Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Adding Annotation to an Error

Purpose

Provide a standard compliant system_error class.

Classes

• bsl::system_error: a standard compliant system_error class

Canonical header: bsl_system_error.h

Description

This component defines class bsl::system_error, a class used for annotated exception objects about errno-style errors. In C++11 mode, the vendor-supplied <system_error> implementation is used instead, and the corresponding names from std are imported into bsl.

Usage

In this section we show intended use of this component.

Example 1: Adding Annotation to an Error

Suppose we want to add an informative message when a system error occurs and include that as part of an exception that we throw when reporting the error. We can use bsl::system_error to do that.

First, reset errno to avoid detecting old problems.

errno = 0;

Then, do something that will fail and set errno.

strtod("1e2000", 0);

Next, check that errno was actually set.

assert(ERANGE == errno);

Finally, prepare an annotated exception and verify the annotation and the error code stored within it.

bsl::system_error annotated(errno, generic_category(), "1e2000");
assert(strstr(annotated.what(), "1e2000"));
assert(static_cast<int>(bsl::errc::result_out_of_range) ==
       annotated.code().value());
assert(&generic_category() == &annotated.code().category());