The LPCXpresso IDE is provided with two different C libraries - Redlib and Newlib, each of which is supplied in a number of library variants. LPCXpresso v7 also introduced a further library, Newlib-Nano, a space optimized version of Newlib.
Normally the library and library variant used by a project are set up when the project is first created using the New Project Wizard. However it is quite simple to switch the selected C library from Redlib <-> Newlib, and switching the library variant in use from Semihost <-> Nohost <-> None. To switch go to:
Quickstart -> Quick Settings -> Set library/header type
and select the required library and variant.
Alternatively, you can make the required changes to your project properties manually as follows...
Repeat the above sequence for all Build Configurations (typically Debug and Release).
Again repeat the above sequence for all Build Configurations (typically Debug and Release). Note the Redlb is not available for C++ projects
Note that if you are providing your own linker script (you are not using the "Manage linker script" option), you will need to add appropriate entries to the linker script detailing the library/variants to use. For more details, please see the FAQ: Using your own linker scripts.