Specifications

CAVR-4

Part 1. Using the compiler

The DLIB runtime environment

Environment interaction

According to the C standard, your application can interact with the environment using

the functions getenv and system.

Note: The

putenv function is not required by the standard, and the library does not

provide an implementation of it.

The

getenv function searches the string, pointed to by the global variable __environ,

for the key that was passed as argument. If the key is found, the value of it is returned,

otherwise 0 (zero) is returned. By default, the string is empty.

To create or edit keys in the string, you must create a sequence of null terminated strings

where each string has the format:

key=value\0

The last string must be empty. Assign the created sequence of strings to the __environ

variable.

For example:

const char MyEnv[] = ”Key=Value\0Key2=Value2\0”;

__environ = MyEnv;

If you need a more sophisticated environment variable handling, you should implement

your own getenv, and possibly putenv function. This does not require that you rebuild

the library. You can find source templates in the files getenv.c and environ.c in the

avr\src\lib directory. For information about overriding default library modules, see

Overriding library modules, page 61.

If you need to use the

system function, you need to implement it yourself. The system

function available in the library simply returns -1.

If you decide to rebuild the library, you can find source templates in the library project

template. For further information, see Building and using a customized library, page 62.

Note: If you link your application with support for I/O debugging, the functions

getenv and system will be replaced by C-SPY variants. For further information, see

Debug support in the runtime library, page 56.

Signal and raise

There are default implementations of the functions signal and raise available. If

these functions do not provide the functionality that you need, you can implement your

own versions.