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C++ exception handling

The ARM compilation tools fully support C++ exception handling. However, the compiler does not support this by default. You must enable C++ exception handling with the --exceptions option. See --exceptions, --no_exceptions for more information.

Note

The Rogue Wave Standard C++ Library is provided with C++ exceptions enabled.

You can exercise limited control over exception table generation.

Function unwinding at runtime

By default, functions compiled with --exceptions can be unwound at runtime. See --exceptions, --no_exceptions for more information. Function unwinding includes destroying C++ automatic variables, and restoring register values saved in the stack frame. Function unwinding is implemented by emitting an exception table describing the operations to be performed.

You can enable or disable unwinding for specific functions with the pragmas #pragma exceptions_unwind and #pragma no_exceptions_unwind, see Pragmas for more information. The --exceptions_unwind option sets the initial value of this pragma.

Disabling function unwinding for a function has the following effects:

  • Exceptions cannot be thrown through that function at runtime, and no stack unwinding occurs for that throw. If the throwing language is C++, then std::terminate is called.

  • A very compact exception table representation can be used to describe the function, that assists smart linkers with table optimization.

  • Function inlining is restricted, because the caller and callee must interact correctly.

Therefore, #pragma no_exceptions_unwind can be used to forcibly prevent unwinding in a way that requires no additional source decoration.

By contrast, in C++ an empty function exception specification permits unwinding as far as the protected function, then calls std::unexpected() in accordance with the ISO C++ Standard.

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