Commit 10e0f0c1 authored by nbruin's avatar nbruin

Document implicit return value behaviour of cdef functions.

parent 7f7851f7
...@@ -160,6 +160,10 @@ with string attributes if they are to be used after the function returns. ...@@ -160,6 +160,10 @@ with string attributes if they are to be used after the function returns.
C functions, on the other hand, can have parameters of any type, since they're C functions, on the other hand, can have parameters of any type, since they're
passed in directly using a normal C function call. passed in directly using a normal C function call.
Functions declared using :keyword:`cdef`, like Python functions, will return a :keyword:`False`
value when execution leaves the function body without an explicit return value. This is in
contrast to C/C++, which leaves the return value undefined.
A more complete comparison of the pros and cons of these different method A more complete comparison of the pros and cons of these different method
types can be found at :ref:`early-binding-for-speed`. types can be found at :ref:`early-binding-for-speed`.
...@@ -216,7 +220,11 @@ returns ``-1``, an exception will be assumed to have occurred and will be ...@@ -216,7 +220,11 @@ returns ``-1``, an exception will be assumed to have occurred and will be
propagated. propagated.
When you declare an exception value for a function, you should never When you declare an exception value for a function, you should never
explicitly return that value. If all possible return values are legal and you explicitly or implicitly return that value. In particular, if the exceptional return value
is a ``False`` value, then you should ensure the function will never terminate via an implicit
or empty return.
If all possible return values are legal and you
can't reserve one entirely for signalling errors, you can use an alternative can't reserve one entirely for signalling errors, you can use an alternative
form of exception value declaration:: form of exception value declaration::
......
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