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RealView Libraries and Floating Point Support Guide
Preface Introduction The C and C++ Libraries About the C and C++ libraries
Features of the C and C++ libraries Namespaces Writing reentrant and thread‑safe code Introduction to reentrancy and thread‑safety Use of static data in the C libraries The __user_libspace static data area Managing locks in multithreaded applications Using the ARM C libraries with a multithreaded app Thread‑safety in the ARM C libraries Thread‑safety in the ARM C++ libraries Building an application with the C library Using the libraries with an application Building an application for a semihosted environme Building an application for a non semihosting envi Building an application without the C library Integer and FP helper functions Bare machine integer C Bare machine C with floating‑point Exploiting the C library The standalone C library functions Tailoring the C library to a new execution environ How C and C++ programs use the library functions __rt_entry Exiting from the program __rt_exit() __rt_lib_init() __rt_lib_shutdown() Tailoring static data access Tailoring locale and CTYPE using assembler macros Selecting locale at link time Selecting locale at runtime Defining a locale block LC_CTYPE data block LC_COLLATE data block LC_MONETARY data block LC_NUMERIC data block LC_TIME data block _get_lconv() localeconv() setlocale() _findlocale() The lconv structure Tailoring locale and CTYPE using C macros Selecting locale at link time Selecting locale at runtime Macros and utility functions _get_lc_ctype() _get_lc_collate() _get_lc_monetary() _get_lc_numeric() _get_lc_time() _get_lconv() localeconv() setlocale() _findlocale() __LC_CTYPE_DEF __LC_COLLATE_DEF __LC_TIME_DEF __LC_NUMERIC_DEF __LC_MONETARY_DEF __LC_INDEX_END The lconv structure Tailoring error signaling, error handling, and pro _sys_exit() errno __rt_errno_addr() __raise() __rt_raise() __default_signal_handler() _ttywrch() __rt_fp_status_addr() Tailoring storage management Avoiding the ARM‑supplied heap and heap‑using Support for malloc Tailoring the runtime memory model The memory models Controlling the runtime memory model Writing your own memory model __user_initial_stackheap() __user_setup_stackheap() __user_heap_extend() __user_heap_extent() __user_stack_cleanup_space() __rt_heap_extend() __rt_stack_postlongjmp() Tailoring the input/output functions Dependencies on low‑level functions Target‑dependent input/output support functions _sys_open() _sys_close() _sys_read() _sys_write() _sys_ensure() _sys_flen() _sys_seek() _sys_istty() _sys_tmpnam() _sys_command_string() #pragma import(_main_redirection) Tailoring other C library functions clock() _clock_init() time() remove() rename() system() getenv() _getenv_init() Selecting real‑time division ISO implementation definition ISO C library implementation definition Standard C++ library implementation definition C library extensions atoll() strtoll() strtoull() printf() snprintf() vsnprintf() lldiv() llabs() wcstombs() alloca() strlcpy() strlcat() _fisatty() __heapstats() __heapvalid() Library naming conventions Placing ARM libraries Helper libraries Identifying library variants The C Micro-library Floating‑point SupportTailoring static data access
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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, such as
malloc(),rand(), andstrtok()functions that do not manage a static state, but use static data in a way that is specific to the implementation in the ARM compiler, 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 2.6. They do not use semihosting.
Table 2.6. C library callouts
| Function | Description |
|---|---|
__rt_errno_addr() | Called to get the address of the variable errno. See __rt_errno_addr(). |
__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(). |
locale functions | The function __user_libspace() creates a block of private static data for the library. See Tailoring locale and CTYPE using assembler macros, and Writing reentrant and thread‑safe code. |
See also Tailoring the runtime memory model 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. However, if you are writing an operating system or a process switcher, you must re‑implement this function (see Writing reentrant and thread‑safe code).
Note
Exactly which functions use static data in their definitions might change in future releases.
| Copyright © 2007 ARM Limited. All rights reserved. | ARM DUI 0378A |
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