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Defined in rt_misc.h, the __raise() function raises a signal to indicate a runtime anomaly.

It is not part of the C library standard, but the ARM® C library supports it as an extension.


int __raise(int signal, intptr_t type);



is an integer that holds the signal number.


is an integer, string constant or variable that provides additional information about the circumstances that the signal was raised in, for some kinds of signal.


If the user has configured the handling of the signal by calling signal() then __raise() takes the action specified by the user. That is, either to ignore the signal or to call the user-provided handler function. Otherwise, __raise() calls __default_signal_handler(), which provides the default signal handling behavior.

You can replace the __raise() function by defining:

int __raise(int signal, intptr_t type);

This enables you to bypass the C signal mechanism and its data-consuming signal handler vector, but otherwise gives essentially the same interface as:

int __default_signal_handler(int signal, intptr_t type);

The default signal handler of the library uses the type parameter of __raise() to vary the messages it outputs.


There are three possibilities for a __raise() return condition:

no return

The handler performs a long jump or restart.


The signal was handled.


The calling code must pass that return value to the exit code. The default library implementation calls _sys_exit(rc) if __raise() returns a nonzero return code rc.