Datasheet

The C and C++ Libraries

4.2 Building an application with the C library

This section covers creating an application that links with functions from the C or C++

libraries. Functions in the C library are responsible for:

• Creating an environment in which a C or C++ program can execute. This includes

— creating a stack

— creating a heap, if required

— initializing the parts of the library the program uses.

• Starting execution by calling

main()

• Supporting use of ISO-defined functions by the program.

• Catching runtime errors and signals and, if required, terminating execution on

error or program exit.

There are three major ways to use the libraries with an application:

• Build a semihosted application that can be debugged in a semihosted environment

such as with ARMulator, Angel, or Multi-ICE. See Building an application for a

semihosted environment.

• Build a nonhosted application that can, for example, be embedded into ROM. See

Building an application for a nonsemihosted environment on page 4-8.

• Build an application that does not use

main()

and does not initialize the library.

This application will have, unless you re-implement some functions, restricted

library functionality. See Building an application without the C library on

page 4-13.

4.2.1 Building an application for a semihosted environment

If you are developing an application to run in a semihosted environment for debugging,

you must have an execution environment that supports the ARM (and typically also

Thumb) semihosting SWIs, and has sufficient memory.

The execution environment can be provided by either:

• using the standard semihosting functionality that is present by default in, for

example, ARMulator, Angel, and Multi-ICE

• implementing your own SWI handler for the semihosting SWI (see ADS Debug

Targe t Gu id e).

A list of functions that require semihosting is given in Overview of semihosting

dependencies on page 4-9.

You are not required to write any new functions or include files if you are using the

default semihosting functionality of the library.