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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

C++ initialization, construction and destruction

1.8.2 C++ initialization, construction and destruction

The C++ Standard places certain requirements on the construction and destruction of objects with static storage duration, and the ARM C++ compiler uses the .init_array area to achieve this.

The .init_array area is a const data array of self-relative pointers to functions. For example, you might have the following C++ translation unit, contained in the file test.cpp:
struct T
{
    T();
    ~T();
} t;
int f()
{
    return 4;
}
int i = f();
This translates into the following pseudocode:
      AREA ||.text||, CODE, READONLY
 int f()
 {
   return 4;
 }
 static void __sti___8_test_cpp
 {
   // construct 't' and register its destruction
   __aeabi_atexit(T::T(&t), &T::~T, &__dso_handle);
   i = f();
 }
      AREA ||.init_array||, DATA, READONLY
      DCD __sti___8_test_cpp - {PC}
      AREA ||.data||, DATA
  t   % 4
  i   % 4
This pseudocode is for illustration only. To see the code that is generated, compile the C++ source code with armcc -c --cpp -S.
The linker collects each .init_array from the various translation units together. It is important that the .init_array is accumulated in the same order.
The library routine __cpp_initialize__aeabi_ is called from the C library startup code, __rt_lib_init, before main. __cpp_initialize__aeabi_ walks through the .init_array calling each function in turn. On exit, __rt_lib_shutdown calls __cxa_finalize.
Usually, there is at most one function call for T::T(), symbol reference _ZN1TC1Ev, one function call for T::~T(), symbol reference _ZN1TD1Ev, one __sti__ function, and four bytes of .init_array for each translation unit. The symbol reference for the function f() is _Z1fv. There is no way to determine the initialization order between translation units.
Function-local static objects with destructors are also handled using __aeabi_atexit.
.init_array sections must be placed contiguously within the same region for their base and limit symbols to be accessible. If they are not, the linker generates an error.
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