Using unsigned char* or signed char* results in a deprecation warning, which is treated as an error. It needs to be casted to regular char* for it to work.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
std::call_once is guaranteed to execute the given callable object
exactly once. This guarantee holds even if the function is called
concurrently from several threads.
Given that, we can replace the mutex and boolean flag with
std::call_once and a std::once_flag to perform the same behavior.
Previously, every entry pair within the map would be copied. The reason
for this is subtle.
A std::map's internal entry type is defined as:
std::pair<const Key, Value>
but the loop was declaring it as:
std::pair<Key, Value>
These two types aren't synonymous with one another and so the compiler
is required to always perform a copy.
Using structured bindings avoids this (as would plain auto or correcting
the explicit type), while also allowing the use of more appropriate
names compared to first and second.
std::function is allowed to heap allocate in order to hold any necessary
bound data in order to execute properly (e.g. lambdas with captures), so
this avoids unnecessary reallocating.
