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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

Legacy support for __user_initial_stackheap()

1.11.4 Legacy support for __user_initial_stackheap()

Defined in rt_misc.h, __user_initial_stackheap() is supported for backwards compatibility with earlier versions of the ARM C and C++ libraries.

Note

ARM recommends that you use __user_setup_stackheap() in preference to __user_initial_stackheap().
The differences between __user_initial_stackheap() and __user_setup_stackheap() are:
  • __user_initial_stackheap() receives the stack pointer (containing the same value it had on entry to __main()) in r1, and is expected to return the new stack base in r1.
    __user_setup_stackheap() receives the stack pointer in sp, and returns the stack base in sp.
  • __user_initial_stackheap() is provided with a small temporary stack to run on. This temporary stack enables __user_initial_stackheap() to be implemented in C, providing that it uses no more than 88 bytes of stack space.
    __user_setup_stackheap() has no temporary stack and cannot usually be implemented in C.
Using __user_setup_stackheap() instead of __user_initial_stackheap() reduces code size, because __user_setup_stackheap() has no requirement for a temporary stack.
In the following circumstances you cannot use the provided __user_setup_stackheap() function, but you can use the __user_initial_stackheap() function:
  • Your implementation is sufficiently complex that it warrants the use of a temporary stack when setting up the initial heap and stack.
  • You have a requirement to implement the heap and stack creation code in C rather than in assembly language.
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