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Libraries and Floating Point Support Guide

Preface The ARM C and C++ Libraries Mandatory linkage with the C library C and C++ runtime libraries Summary of the C and C++ runtime libraries Compliance with the Application Binary Interface ( Increasing portability of object files to other CL ARM C and C++ library directory structure Selection of ARM C and C++ library variants based Thumb C libraries C and C++ library features C++ and C libraries and the std namespace Multithreaded support in ARM C libraries ARM C libraries and multithreading ARM C libraries and reentrant functions ARM C libraries and thread-safe functions Use of static data in the C libraries Use of the __user_libspace static data area by the C library functions to access subsections of the _ Re-implementation of legacy function __user_libspa Management of locks in multithreaded applications How to ensure re-implemented mutex functions are c Using the ARM C library in a multithreaded environ Thread safety in the ARM C library Thread safety in the ARM C++ library The floating-point status word in a multithreaded Support for building an application with the C lib Using the C library with an application Using the C and C++ libraries with an application Using $Sub$$ to mix semihosted and nonsemihosted I Using the libraries in a nonsemihosting environmen C++ exceptions in a non-semihosting environment Direct semihosting C library function dependencies Indirect semihosting C library function dependenci C library API definitions for targeting a differen Support for building an application without the C Building an application without the C library Creating an application as bare machine C without Integer and floating-point compiler functions and Bare machine integer C Bare machine C with floating-point processing Customized C library startup code and access to C Using low-level functions when exploiting the C li Using high-level functions when exploiting the C l Using malloc() when exploiting the C library Tailoring the C library to a new execution environ Initialization of the execution environment and ex C++ initialization, construction and destruction Exceptions system initialization Emergency buffer memory for exceptions Library functions called from main() Program exit and the assert macro Assembler macros that tailor locale functions in t Link time selection of the locale subsystem in the Runtime selection of the locale subsystem in the C Definition of locale data blocks in the C library LC_CTYPE data block LC_COLLATE data block LC_MONETARY data block LC_NUMERIC data block LC_TIME data block Modification of C library functions for error sign Stack and heap memory allocation and the ARM C and Library heap usage requirements of the ARM C and C Choosing a heap implementation for memory allocati Stack pointer initialization and heap bounds Legacy support for __user_initial_stackheap() Avoiding the heap and heap-using library functions Tailoring input/output functions in the C and C++ Target dependencies on low-level functions in the The C library printf family of functions The C library scanf family of functions Redefining low-level library functions to enable d The C library functions fread(), fgets() and gets( Re-implementing __backspace() in the C library Re-implementing __backspacewc() in the C library Redefining target-dependent system I/O functions i Tailoring non-input/output C library functions Real-time integer division in the ARM libraries ISO C library implementation definition How the ARM C library fulfills ISO C specification mathlib error handling ISO-compliant implementation of signals supported ISO-compliant C library input/output characteristi Standard C++ library implementation definition C library functions and extensions Compiler generated and library-resident helper fun C and C++ library naming conventions Using macro__ARM_WCHAR_NO_IO to disable FILE decla Using library functions with execute-only memory The ARM C Micro-library Floating-point Support The C and C++ Library Functions reference Floating-point Support Functions Reference

Target dependencies on low-level functions in the C and C++ libraries

1.13 Target dependencies on low-level functions in the C and C++ libraries

Higher-level C and C++ library input/output functions are built upon lower-level functions. If you define your own versions of the lower-level functions, you can use the library versions of the higher-level functions directly.

The following table shows the dependencies of the higher-level functions on lower-level functions.
fgetc() uses __FILE, but fputc() uses __FILE and ferror().


  • You must provide definitions of __stdin and __stdout if you use any of their associated high-level functions. This applies even if your re-implementations of other functions, such as fgetc() and fputc(), do not reference any data stored in __stdin and __stdout.
  • When targeting the strict ANSI C standard, you must provide your own implementation of the __FILE structure. For example:
    struct __FILE { int handle; /* Add whatever you need here */ };
  • If you choose to re-implement fgetc(), fputc(), and __backspace(), be aware that fopen() and related functions use the ARM layout for the __FILE structure. You might also have to re-implement fopen() and related functions if you define your own version of __FILE.
Table key:
  1. __FILE, the file structure.
  2. __stdin, the standard input object of type __FILE.
  3. __stdout, the standard output object of type __FILE.
  4. fputc(), outputs a character to a file.
  5. ferror(), returns the error status accumulated during file I/O.
  6. fgetc(), gets a character from a file.
  7. fgetwc()
  8. fputwc()
  9. __backspace(), moves the file pointer to the previous character.
  10. __backspacewc().

Table 1-9 Input/output dependencies

High-level function Low-level object  
  1 2 3 4 5 6 7 8 9 10
fgets x - - - x x - - - -
fgetws x - - - - - x - - -
fprintf x - - x x - - - - -
fputs x - - x - - - - - -
fputws x - - - - - - x - -
fread x - - - - x - - - -
fscanf x - - - - x - - x -
fwprintf x - - - x - - x - -
fwrite x - - x - - - - - -
fwscanf x - - - - - x - - x
getchar x x - - - x - - - -
gets x x - - x x - - - -
getwchar x x - - - - x - - -
perror x - x x - - - - - -
printf x - x x x - - - - -
putchar x - x x - - - - - -
puts x - x x - - - - - -
putwchar x - x - - - - x - -
scanf x x - - - x - - x -
vfprintf x - - x x - - - - -
vfscanf x - - - - x - - x -
vfwprintf x - - - x - - x - -
vfwscanf x - - - - - x - - x
vprintf x - x x x - - - - -
vscanf x x - - - x - - x -
vwprintf x - x - x - - x - -
vwscanf x x - - - - x - - x
wprintf x - x - x - - x - -
wscanf x x - - - - x - - x
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