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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

Redefining low-level library functions to enable direct use of high-level library functions in the C library

1.16 Redefining low-level library functions to enable direct use of high-level library functions in the C library

If you define your own version of __FILE, your own fputc() and ferror() functions, and the __stdout object, you can use all of the printf() family, fwrite(), fputs(), puts() and the C++ object std::cout unchanged from the library.

These examples show you how to do this. However, consider modifying the system I/O functions instead of these low-level library functions if you require real file handling.
You are not required to re-implement every function shown in these examples. Only re-implement the functions that are used in your application.

Retargeting printf()

#include <stdio.h>
struct __FILE
{
  int handle;
  /* Whatever you require here. If the only file you are using is */
  /* standard output using printf() for debugging, no file handling */
  /* is required. */
};
/* FILE is typedef’d in stdio.h. */
FILE __stdout;
int fputc(int ch, FILE *f) 
{
  /* Your implementation of fputc(). */
  return ch;
}
int ferror(FILE *f)
{
  /* Your implementation of ferror(). */
  return 0;
}
void test(void)
{
  printf("Hello world\n");
}

Note

Be aware of endianness with fputc(). fputc() takes an int parameter, but contains only a character. Whether the character is in the first or the last byte of the integer variable depends on the endianness. The following code sample avoids problems with endianness:
extern void sendchar(char *ch);
int fputc(int ch, FILE *f)
{
  /* example: write a character to an LCD */
  char tempch = ch;  // temp char avoids endianness issue
  sendchar(&tempch); // sendchar(&ch) would not work everywhere
  return ch;
}

Retargeting cout

File 1: Re-implement any functions that require re-implementation.
#include <stdio.h>
namespace std {
  struct __FILE
  {
    int handle;
    /* Whatever you require here. If the only file you are using is */
    /* standard output using printf() for debugging, no file handling */
    /* is required. */
  };
  FILE __stdout;
  FILE __stdin;
  FILE __stderr;
  int fgetc(FILE *f)
  {
    /* Your implementation of fgetc(). */
    return 0;
  }
  int fputc(int c, FILE *stream)
  {
    /* Your implementation of fputc(). */
  }
  int ferror(FILE *stream)
  {
    /* Your implementation of ferror(). */
  }
  long int ftell(FILE *stream)
  {
    /* Your implementation of ftell(). */
  }
  int fclose(FILE *f)
  {
    /* Your implementation of fclose(). */
    return 0;
  }
  int fseek(FILE *f, long nPos, int nMode)
  {
    /* Your implementation of fseek(). */
    return 0;
  }
  int fflush(FILE *f)
  {
    /* Your implementation of fflush(). */    
    return 0;
  }
}
File 2: Print "Hello world" using your re-implemented functions.
#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
  cout << "Hello world\n";
  return 0;
}
By default, fread() and fwrite() call fast block input/output functions that are part of the ARM stream implementation. If you define your own __FILE structure instead of using the ARM stream implementation, fread() and fwrite() call fgetc() instead of calling the block input/output functions.
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