# Building GEOS on CentOS

It should be simple, but I ran into a number of errors.

First I got stuck on `libtool: line 990: g++: command not found`. It turns out I needed to install `g++` using:

`yum install gcc-c++`

Then I got stuck on this one:

```platform.h:110:2: error: #error "Can not compile without isnan function or macro
[...]
"Coordinate.inl:38: error: ‘ISNAN’ was not declared in this scope```

The author of this page faced the problem, but the real insight came from this bug report on an unrelated project:

In these versions of g++ `isnan` is defined as a macro in unless is included, in which case `std::isnan()` is defined instead.

And so I tried replacing `#include <math.h>` with `#include <cmath>` in `include/geos/platform.h`. Amazingly, that worked.