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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 implementation of signals supported by the signal() function in the C library and additional type arguments

1.23.3 ISO-compliant implementation of signals supported by the signal() function in the C library and additional type arguments

The signal() function supports a number of signals.

The following table shows the signals supported by the signal() function. It also shows which signals use an additional argument to give more information about the circumstance in which the signal was raised. The additional argument is given in the type parameter of __raise(). For example, division by floating-point zero results in a SIGFPE signal with a corresponding additional argument of FE_EX_DIVBYZERO.

Table 1-10 Signals supported by the signal() function

Signal Number Description Additional argument
Returned when the abort() function is called.
The abort() function is triggered when there is an untrapped C++ exception, or when an assertion fails.
SIGFPE 2 Signals any arithmetic exception, for example, division by zero. Used by hard and soft floating-point and by integer division. A set of bits from FE_EX_INEXACT, FE_EX_UNDERFLOW, FE_EX_OVERFLOW, FE_EX_DIVBYZERO, FE_EX_INVALID, DIVBYZERO a
SIGILL 3 Illegal instruction. None
SIGINT b 4 Attention request from user. None
SIGSEGV b 5 Bad memory access. None
SIGTERM b 6 Termination request. None
SIGSTAK 7 Obsolete. None
SIGRTRED 8 Redirection failed on a runtime library input/output stream. Name of file or device being re-opened to redirect a standard stream
SIGRTMEM 9 Out of heap space during initialization or after corruption. Size of failed request
SIGUSR1 10 User-defined. User-defined
SIGUSR2 11 User-defined. User-defined
SIGPVFN 12 A pure virtual function was called from C++. -
Not normally used.
reserved 15-31 Reserved. Reserved
other > 31 User-defined. User-defined
Although SIGSTAK exists in signal.h, this signal is not generated by the C library and is considered obsolete.
A signal number greater than SIGUSR2 can be passed through __raise() and caught by the default signal handler, but it cannot be caught by a handler registered using signal().
signal() returns an error code if you try to register a handler for a signal number greater than SIGUSR2.
The default handling of all recognized signals is to print a diagnostic message and call exit(). This default behavior applies at program startup and until you change it.


The IEEE 754 standard for floating-point processing states that the default action to an exception is to proceed without a trap. A raised exception in floating-point calculations does not, by default, generate SIGFPE. You can modify floating-point error handling by tailoring the functions and definitions in fenv.h. However, you must compile these functions with a non-default FP model, such as --fpmode=ieee_fixed and upwards.
For all the signals in the above table, when a signal occurs, if the handler points to a function, the equivalent of signal(sig, SIG_DFL) is executed before the call to the handler.
If the SIGILL signal is received by a handler specified to by the signal() function, the default handling is reset.
These constants are defined in fenv.h. FE_EX_DIVBYZERO is for floating-point division while DIVBYZERO is for integer division.
The library never generates this signal. It is available for you to raise manually, if required.
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