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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

ISO-compliant C library input/output characteristics

1.23.4 ISO-compliant C library input/output characteristics

The generic ARM C library has defined input/output characteristics.

These input/output characteristics are as follows:
  • The last line of a text stream does not require a terminating newline character.
  • Space characters written out to a text stream immediately before a newline character do appear when read back in.
  • No NUL characters are appended to a binary output stream.
  • The file position indicator of an append mode stream is initially placed at the end of the file.
  • A write to a text stream causes the associated file to be truncated beyond the point where the write occurred if this is the behavior of the device category of the file.
  • If semihosting is used, the maximum number of open files is limited by the available target memory.
  • A zero-length file exists, that is, where no characters have been written by an output stream.
  • A file can be opened many times for reading, but only once for writing or updating. A file cannot simultaneously be open for reading on one stream, and open for writing or updating on another.
  • stdin, stdout, and stderr, are interactive devices, but are line-buffered at program startup.
  • localtime() is implemented and returns the local time. gmtime() is not implemented and returns NULL. Therefore converting between time-zones is not supported.
  • The status returned by exit() is the same value that was passed to it. For definitions of EXIT_SUCCESS and EXIT_FAILURE, see the header file stdlib.h. Semihosting, however, does not pass the status back to the execution environment.
  • The error messages returned by the strerror() function are identical to those given by the perror() function.
  • If the size of area requested is zero, calloc() and realloc() return NULL.
  • If the size of area requested is zero, malloc() returns a pointer to a zero-size block.
  • abort() closes all open files and deletes all temporary files.
  • fprintf() prints %p arguments in lowercase hexadecimal format as if a precision of 8 had been specified. If the variant form (%#p) is used, the number is preceded by the character @.
  • fscanf() treats %p arguments exactly the same as %x arguments.
  • fscanf() always treats the character "-" in a %...[...] argument as a literal character.
  • ftell(), fsetpos() and fgetpos() set errno to the value of EDOM on failure.
  • perror() generates the messages shown in the following table.

Table 1-11 perror() messages

Error Message
0 No error (errno = 0)
EDOM EDOM - function argument out of range
ERANGE ERANGE - function result not representable
ESIGNUM ESIGNUM - illegal signal number
Others Unknown error
The following characteristics are unspecified in the ARM C library. They must be specified in an ISO-compliant implementation:
  • The validity of a filename.
  • Whether remove() can remove an open file.
  • The effect of calling the rename() function when the new name already exists.
  • The effect of calling getenv() (the default is to return NULL, no value available).
  • The effect of calling system().
  • The value returned by clock().
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