BOOST libraries in multithreading-aware mode

Question

There is a possibility to compile BOOST libraries in the so-called thread-aware mode. If so you will see "...-mt..." appeared in the library name. I can't understand what it gives me and when do I need to use such mode? Does it give me any benefits?

More than that I'm really confused by having BOOST Threads library compiled in NO-thread-aware regime (with no -mt in the name). It does not make any sense for me. Looks self-contradictory :/

Thanks a lot for any help!

Answer 1

Because you did not specify how you have built, and on what platform, I'll explain the whole story. Both on Linux and Windows, Boost.Thread library is built in MT mode. On Windows, by default, you get -mt suffix for it. On Linux, by default in 1.42, you get no suffix. The reason you get no suffix on Linux is that pretty much no other library uses such convention, and it's much less important on Linux anyway.

Does this clarify things?

Answer 2

There is an option to put "-mt" suffix back (bjam --layout=tagged)

--layout=<layout>     Determines whether to choose library names                       and header locations such that multiple                       versions of Boost or multiple compilers can                       be used on the same system.                            versioned - Names of boost binaries                           include the Boost version number, name and                           version of the compiler and encoded build                           properties.  Boost headers are installed in a                           subdirectory of <HDRDIR> whose name contains                           the Boost version number.                            tagged -- Names of boost binaries include the                           encoded build properties such as variant and                           threading, but do not including compiler name                           and version, or Boost version. This option is                           useful if you build several variants of Boost,                           using the same compiler.                            system - Binaries names do not include the                           Boost version number or the name and version                           number of the compiler.  Boost headers are                           installed directly into <HDRDIR>.  This option                           is intended for system integrators who are                           building distribution packages.                        The default value is 'versioned' on Windows, and                       'system' on Unix. 

Answer 3

MT enables multithreaded support in the boost libraries meaning you are safe to use them in your multithreaded programs (at least from the library's internal code point of view).

And indeed building the threads library in the "no threads" mode does not make any sense but I was under the impression that that specific build target is disabled.

Check these out

http://sodium.resophonic.com/boost-cmake/current-docs/build_variants.html

http://www.boost.org/doc/libs/1_41_0/more/getting_started/windows.html#library-naming

Answer 4

You can build Boost with multi-threading support or not (threading=multi|single). Boost.Thread force the build of the library by setting threading=multi in its Jamfile (the bjam equivalent of a Makefile).

So independently of whether you request threading support or not, Boost.Thread always provide it. Hence you can find both names.

Answer 5

Since, under Linux, the -mt version is aliased/bound to the regular version, it makes no difference. In a vanilla modern system, both are simply included for ease of compilation.