### 2.7 Compiler, Tools and Run-Time libraries Options

The following environment variables can be used to override configure's guess at what compilers to use:

- `CC`: the C compiler
- `ADA`: the Ada compiler (e.g. gcc, gnatgcc or adagcc)
- `CXXCPP`, `CXXCPPFLAGS`: the preprocessor used by the IDL-to-Ada compiler (only when setting up the CORBA application personality). CORBA specifications require this preprocessor to be compatible with the preprocessing rules defined in the C++ programming language specifications.

For example, if you have two versions of GNAT installed and available in your `PATH`, and configure picks the wrong one, you can indicate what compiler should be used with the following (assuming Bourne shell syntax):

           $ ADA=/path/to/good/compiler/gcc ./configure [options]

PolyORB will be compiled with GNAT build host's configuration, including run-time library. You may override this setting using `ADA_INCLUDE_PATH` and `ADA_OBJECTS_PATH` environment variables. See GNAT User's Guide for more details.

You can add specific build options to GNAT using the `EXTRA_GNATMAKE_FLAGS` variable:

           $ EXTRA_GNATMAKE_FLAGS=--RTS=rts-sjlj ./configure [options]

You can also pass compiler-only flags using the `ADAFLAGS` variable.

NOTE: Developers building PolyORB from the version control repository will need to rebuild the configure script and other files. To do so, from the top-level source directory, run the support/reconfig script after each update from the repository. In addition to the requirements above, developers will need autoconf 2.57 or newer, automake 1.6.3 or newer, and libtool 1.5.8 or newer.