ARM VERSION 1.2 Arkusz Danych Pobierz pdf (Strona 105)

The C and C++ Libraries

Program design

The functions you must re-implement depend on how much of the library functionality

you require as follows:

• If you want only the compiler support functions for division, structure copy, and

FP arithmetic, you must provide

__rt_raise()

. This also enables very simple

library functions such as those in

errno.h

setjmp.h

, and most of

string.h

to work.

• If you call

setlocale()

explicitly, locale-dependent functions start to work. This

enables you to use the

atoi

family,

sprintf()

sscanf()

, and the functions in

ctype.h

• Programs that use floating-point must call

_fp_init()

. If you select software

floating-point, the program must also provide

__rt_fp_status_addr()

. (The

default action is this function is not reimplemented is to create a user libspace

area.

• Implementing high-level input/output support is necessary for functions that use

fprintf()

fputs()

. The high-level output functions depend on

fputc()

and

ferror()

. The high-level input functions depend on

fgetc()

and

__backspace()

• Implementing the above functions and the heap enables you to use almost the

entire library.

Using low-level functions

If you are using the libraries in an application that does not have a

main()

function, you

must re-implement some functions in the library. See The standalone C library

functions on page 4-16 for a detailed list of functions that are not available, functions

that are available without modification, and functions that are available after other

lower-level functions are re-implemented.

__rt_raise()

is essential. It is required by all FP functions, by integer division so that

divide-by-zero can be reported, and by some other library routines. You probably cannot

write a nontrivial program without doing something that requires

__rt_raise()

Note

rand()

is called,

srand()

must be called first. This is done automatically during library

initialization but not when you avoid the library initialization.

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