Using AFIO really slows down my compile times. Can't you do something about that?

You'll find a huge amount depends on your compiler. Here are some build time benchmarks for my developer workstation:

Table 1.17. Single thread build times for AFIO v1.3 for various compilers and options on a 3.5Ghz Intel Core i7 3770K

Build flags	Microsoft Windows 8.1 x64 with Visual Studio 2013	Ubuntu 14.04 LTS Linux x64 with GCC 4.9 and gold linker	Ubuntu 14.04 LTS Linux x64 with clang 3.4 and gold linker
`--link-test --fast-build debug`	0m55s	3m53s	asio failure
`--link-test debug`	2m10s	10m26s	5m46s
`--link-test --lto debug`	5m37s	GCC ICE	5m42s
`--link-test pch=off debug`	7m17s	12m0s	5m45s
`--link-test --fast-build release`	1m10s	3m22s	asio failure
`--link-test release`	2m58s	9m57s	8m10s
`--link-test --lto release`	7m30s	13m0s	8m11s
standalone alltests release	0m20s	0m51s	0m42s
standalone multiabi alltests release	0m39s	1m34s	1m13s

Table 1.18. Single thread build times for AFIO v1.2 for various compilers and options on a 3.5Ghz Intel Core i7 3770K

Build flags	Microsoft Windows 8 x64 with Visual Studio 2013	Ubuntu 12.04 LTS Linux x64 with GCC 4.8 and gold linker	Ubuntu 12.04 LTS Linux x64 with clang 3.4 and gold linker
`--link-test --fast-build debug`	01m43s	03m31s^[a]	fails
`--link-test debug`	02m40s	06m15s	04m24s
`--link-test --lto debug`	09m36s	06m23s	04m32s
`--link-test pch=off debug`	06m12s	08m01s	04m26s
`--link-test --fast-build release`	02m01s	03m15s^[b]	fails
`--link-test release`	03m09s	06m28s	06m06s
`--link-test --lto release`	10m24s	07m08s	06m14s
^[a] ASIO has a link error without `link=static` ^[b] ASIO has a link error without `link=static`

You'll note that v1.3 is substantially faster than v1.2 to build on MSVC for some odd reason, despite considerably more metaprogramming, code, and tests. The rises in times like with GCC and clang make more sense.

The benefit of --fast-build grows exponentially the less powerful the CPU: on my Intel Atom 220 netbook --fast-build gets total build times under five minutes which is impressive compared to the twenty or so minutes without that flag.

--fast-build works by defining BOOST_AFIO_HEADERS_ONLY to 0 for each compiland, and linking to the AFIO shared library instead. It also does the same for ASIO by defining BOOST_ASIO_SEPARATE_COMPILATION and BOOST_ASIO_DYN_LINK for each compiland, and links to the ASIO shared library instead (which is built via boost/asio/impl/src.hpp, see ASIO's docs).