ARM VERSION 1.2 Datový list stáhnout pdf (Strana 115)

The C and C++ Libraries

4.5 Tailoring static data access

This section describes using callouts from the C library to access static data. C library

functions that use static data can be categorized as follows:

• functions that do not use any static data of any kind, for example

fprintf()

• functions that manage a static state, for example

malloc()

rand()

, and

strtok()

• functions that do not manage a static state, but use static data in a way that is

specific to their ARM implementation, for example

isalpha()

When the C library does something that requires implicit static data, it uses a callout to

a function you can replace. These functions are shown in Table 4-5.

The functions above do not use semihosting.

See also Tailoring the runtime memory model on page 4-67 for more information about

memory use.

The default implementation of

__user_libspace()

creates a 96-byte block in the ZI

segment. Even if your application does not have a

main()

function, the

__user_libspace()

function does not normally have to be redefined. (If you are writing

an operating system or a process switcher, however, you must retarget this function.)

Caution

The number of functions that use static data in their definitions might change in future

versions of ADS.

Table 4-5 Callouts

Function Description

__rt_errno_addr()

Called to get the address of the variable

errno

. See

__rt_errno_addr() on page 4-53.

__rt_fp_status_addr()

Called by the floating-point support code to get the

address of the floating-point status word. See

__rt_fp_status_addr() on page 4-56.

The

locale

functions The function

__user_libspace()

creates a block of private

static data for the library. See Tailoring locale and CTYPE

on page 4-26.

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