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## Building and Installing the Library

When you extract the library from its zip file, you must preserve its internal directory structure (for example by using the -d option when extracting). If you didn't do that when extracting, then you'd better stop reading this, delete the files you just extracted, and try again!

This library should not need configuring before use; most popular compilers/standard libraries/platforms are already supported "as is". If you do experience configuration problems, or just want to test the configuration with your compiler, then the process is the same as for all of boost; see the configuration library documentation.

The library will encase all code inside namespace boost.

Unlike some other template libraries, this library consists of a mixture of template code (in the headers) and static code and data (in cpp files). Consequently it is necessary to build the library's support code into a library or archive file before you can use it, instructions for specific platforms are as follows:

##### Building with bjam

This is now the preferred method for building and installing this library, please refer to the getting started guide for more information.

##### Building With Unicode and ICU Support

Boost.Regex is now capable of performing a configuration check to test whether ICU is already installed in your compiler's search paths. When you build you should see a message like this:

    Performing configuration checks

        - has_icu builds           : yes

Which means that ICU has been found, and support for it will be enabled in the library build.

| Tip
If you don't want the regex library to use ICU then build with the "--disable-icu" command line option.

If instead you see:

    Performing configuration checks

        - has_icu builds           : no

Then ICU was not found and support for it will not be compiled into the library. If you think that it should have been found, then you will need to take a look at the contents of the file boost-root/bin.v2/config.log for the actual error messages obtained when the build carried out the configuration check. You will then need to fix these errors by ensuring your compiler gets invoked with the correct options, for example:

    bjam include=some-include-path --toolset=toolset-name install

will add "some-include-path" to your compilers header include path, or if ICU has been built with non-standard names for it's binaries, then:

    bjam -sICU_LINK="linker-options-for-icu" --toolset=toolset-name install

Will use "linker-options-for-icu" when linking the library rather than the default ICU binary names.

You might also need to use the options "cxxflags=-option" and "linkflags=-option" to set compiler and linker specific options.

| Important
Configuration results are cached - if you try rebuilding with different compiler options then add an "-a" to the bjam command line to force all targets to be rebuilt.

If ICU is not already in your compiler's path, but instead headers, libraries and binaries are located at path-to-icu/include, path-to-icu/lib and path-to-icu/bin respectively then you need to set the environment variable `ICU_PATH` to point to the root directory of your ICU installation: this typically happens if you're building with MSVC. For example if ICU was installed to `c:\download\icu` you might use:

    bjam -sICU_PATH=c:\download\icu --toolset=toolset-name install

| Important
ICU is a C++ library just like Boost is, as such your copy of ICU must have been built with the same C++ compiler (and compiler version) that you are using to build Boost. Boost.Regex will not work correctly unless you ensure that this is the case: it is up to you to ensure that the version of ICU you are using is binary compatible with the toolset you use to build Boost.

And finally, if you want to build/test with multiple compiler versions, all with different ICU builds, then the only way to achieve that currently is to modify your user-config.jam so that each toolset has the necessary compiler/linker options set so that ICU is found automatically by the configuration step (providing the ICU binaries use the standard names, all you have to add is the appropriate header-include and linker-search paths).

##### Building from Source

The Regex library is "just a bunch of source files": nothing special is required to build them.

You can either build the files under boost-path/libs/regex/src/*.cpp as a library, or add them directly to your project. This is particularly useful if you need to use specific compiler options not supported by the default Boost build.

There are two #defines you should be aware of:

- BOOST_HAS_ICU should be defined if you want ICU support compiled in.
- BOOST_REGEX_DYN_LINK should be defined if you are building a DLL on Windows.