7 Expressions [expr]

7.6 Compound expressions [expr.compound]

7.6.18 Throwing an exception [expr.throw]

1
#
A throw-expression is of type void.
2
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A throw-expression with an operand throws an exception ([except.throw]).
The array-to-pointer ([conv.array]) and function-to-pointer ([conv.func]) standard conversions are performed on the operand.
The type of the exception object is determined by removing any top-level cv-qualifiers from the type of the (possibly converted) operand.
The exception object is copy-initialized ([dcl.init.general]) from the (possibly converted) operand.
3
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A throw-expression with no operand rethrows the currently handled exception ([except.handle]).
If no exception is presently being handled, the function std​::​terminate is invoked ([except.terminate]).
Otherwise, the exception is reactivated with the existing exception object; no new exception object is created.
The exception is no longer considered to be caught.
[Example 1: 
An exception handler that cannot completely handle the exception itself can be written like this: try { // ... } catch (...) { // catch all exceptions // respond (partially) to exception throw; // pass the exception to some other handler }
— end example]