Comtrol eCos - Manual (Page 58)

Exception handling
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The data argument corresponds to the new_data parameter supplied to cyg_exception_set_handler . The
exception code is provided as well, in case a single handler is expected to support multiple exceptions. The info
argument will depend on the hardware and on the specific exception.
cyg_exception_clear_handler can be used to restore the default handler, if desired. It is also possible for
software to raise an exception and cause the current handler to be invoked, but generally this is useful only for
testing.
By default the system maintains a single set of global exception handlers. However, since exceptions
occur synchronously it is sometimes useful to handle them on a per-thread basis, and have a different
set of handlers for each thread. This behaviour can be obtained by disabling the configuration
option
CYGSEM_KERNEL_EXCEPTIONS_GLOBAL . If per-thread exception handlers are being used then
cyg_exception_set_handler and cyg_exception_clear_handler apply to the current thread. Otherwise
they apply to the global set of handlers.
Caution
In the current implementation cyg_exception_call_handler can only be used on the current
thread. There is no support for delivering an exception to another thread.
Note: Exceptions at the eCos kernel level refer specifically to hardware-related events such as unaligned
accesses to memory or division by zero. There is no relation with other concepts that are also known as
exceptions, for example the
throw and catch facilities associated with C++.
Valid contexts
If the system is configured with a single set of global exception handlers then cyg_exception_set_handler
and cyg_exception_clear_handler may be called during initialization or from thread context. If instead per-
thread exception handlers are being used then it is not possible to install new handlers during initialization be-
cause the functions operate implicitly on the current thread, so they can only be called from thread context.
cyg_exception_call_handler should only be called from thread context.
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