Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
The library declares the boost::log namespace
which should be used in client code to access library components. However,
internally the library uses another nested namespace for actual implementation.
The namespace name is configuration and platform dependent, it can change
between different releases of the library, so it should never be used in
the user side code. This is done in order to make the library configuration
synchronized with the application as much as possible and eliminate problems
caused by configuration mismatch.
Most of the time users won't even notice the existence of this internal namespace, but it often appears in compiler and linker errors and in some cases it is useful to know how to decode its name. Currently, the namespace name is composed from the following elements:
<version><linkage>_<threading>_<system>
<version> component describes the library major
version. It is currently v2.
<linkage> component tells whether the library
is linked statically or dynamically. It is s
if the library is linked statically and empty otherwise.
<threading> component is st
for single-threaded builds and mt
for multi-threaded ones.
<system> component describes the underlying
OS API used by the library. Currently, it is only specified for multi-threaded
builds. Depending on the target platform and configuration, it can be
posix, nt5 or nt6.
As a couple quick examples, v2s_st
corresponds to v2 static single-threaded build of the library and v2_mt_posix - to v2 dynamic multi-threaded
build for POSIX system API.
Namespace mangling may lead to linking errors if the application is misconfigured.
One common mistake is to build dynamic version of the library and not define
BOOST_LOG_DYN_LINK or BOOST_ALL_DYN_LINK when building the application,
so that the library assumes static linking by default. Whenever such linking
errors appear, one can decode the namespace name in the missing symbols and
the exported symbols of Boost.Log library and adjust library or application
configuration accordingly.