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Modification of C library functions for error signaling, error handling, and program exit

Note

The ARM Compiler toolchain does not support floating-point exception trapping for AArch64 targets.

All trap or error signals raised by the C library go through the __raise() function. You can re-implement this function or the lower-level functions that it uses.

The IEEE 754 standard for floating-point processing states that the default response to an exception is to proceed without a trap. You can modify floating-point error handling by tailoring the functions and definitions in fenv.h.

The rt_misc.h header file contains more information on error-related functions.

The trap and error-handling functions are shown in Table 8.

Table 8. Trap and error handling
FunctionDescription
_sys_exit()Called, eventually, by all exits from the library.
errnoIs a static variable used with error handling.
__rt_errno_addr()Is called to obtain the address of the variable errno.
__raise()Raises a signal to indicate a runtime anomaly.
__rt_raise()Raises a signal to indicate a runtime anomaly.
__default_signal_handler()Displays an error indication.
_ttywrch()Writes a character to the console. The default implementation of _ttywrch() is semihosted and, therefore, uses semihosting calls.
__rt_fp_status_addr()This function is called to obtain the address of the floating-point status word.

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