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:

the desired effect cannot be accomplished with a C++11 standard language feature, and
a C++ standard library equivalent is either unavailable or unusable with our minimum supported compiler version (i.e. gcc version 4.8).

In particular, the following Boost libraries are no longer accepted as they have standard equivalents in gcc 4.8 and above:

array: use <array>
bind: prefer C++11 lambda functions instead, but use std::bind from <functional> if you must
cstdint: use <cstdint>
filesystem: use <filesystem>
lambda: use C++11 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++11 static_assert
tuple: use <tuple>
type_traits: use <type_traits>
unordered_map: use <unordered_map>

Certain Boost libraries are recommended: they should be used whenever applicable in preference to any other method of accomplishing the same effect. In general, any library that is tagged with “Standard .... {something}” in the Boost library listing falls into this category (unless its use conflicts with the above rules on the availability of standard library / language equivalents). Among others, this category includes:

current_function
format
regex
test

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

any
GIL
iterator
MPI
multi_index
numeric
tokenizer
variant

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 (is not listed on the above page as “Build & Link .... Header-only”). Among others, the following libraries fall into the extra-caution category:

Fusion
MPL
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