This program appears to use heap allocation, at least indirectly through its use of std::string.
On a more general note, libraries that perform zero dynamic allocation (and instead require the library user to pass in memory) can be very convenient for systems programming where portability is a concern. For example, I use Intel XED instruction encoder/decoder, which is a library that performs no dynamic memory allocation. This allows me to use it in user space and kernel space without hijacking the malloc symbol.
On a more general note, libraries that perform zero dynamic allocation (and instead require the library user to pass in memory) can be very convenient for systems programming where portability is a concern. For example, I use Intel XED instruction encoder/decoder, which is a library that performs no dynamic memory allocation. This allows me to use it in user space and kernel space without hijacking the malloc symbol.