Using Boost

Note

Changes to this document must be approved by the System Architect (RFC-24). To request changes to these policies, please file an RFC.

A Boost library may be used only if:

  1. the desired effect cannot be accomplished with a C++17 standard language feature, and

  2. a C++ standard library equivalent is either unavailable or unusable with our minimum required compiler version.

In particular, the following Boost libraries are no longer accepted as they have standard equivalents in gcc 6.3.1 and above:

any

use <any>

array

use <array>

bind

prefer C++14 lambda functions instead, but use std::bind from <functional> if you must

cstdint

use <cstdint>

filesystem

use <filesystem>

lambda

use C++14 lambda functions

lexical_cast

use std::to_string, std::stoi, std::stod etc.

math

use <cmath> wherever possible

noncopyable

use = delete on the copy constructor and assignment operator

random

use <random>

ref

use std::forward and universal / forwarding references (or std::ref if you must)

smart_ptr

use std::shared_ptr and std::unique_ptr (and its array specialization) from <memory> instead of boost::shared_ptr, boost::scoped_ptr and boost::scoped_array

static_assert

use C++14 static_assert

tuple

use <tuple>

type_traits

use <type_traits>

unordered_map

use <unordered_map>

variant

use <variant>

Certain Boost libraries are recommended: they should be used whenever applicable in preference to any other method of accomplishing the same effect. Among others, this category includes:

  • current_function

  • format

  • test

Additional Boost libraries are considered safe: they may be used freely where applicable.

  • GIL

  • iterator

  • MPI

  • multi_index

  • numeric

  • tokenizer

Most other Boost libraries may be used after appropriate design review. Particular caution should be used when the library involves substantial template metaprogramming or requires linking. Among others, the following libraries fall into the extra-caution category:

  • Fusion

  • MPL

  • regex

  • serialization

Certain Boost libraries conflict with LSST-standard ways of doing things, are inappropriate for LSST code, are insufficiently developed or well-maintained, or have been found to be excessively complicated. These are not allowed without special permission.

  • config

  • preprocessor

  • python

  • throw_exception