Using aout
– A Concurrency-safe Wrapper for cout
¶
When using cout
from multiple actors, output often appears
interleaved. Moreover, using cout
from multiple actors – and thus
from multiple threads – in parallel should be avoided regardless, since the
standard does not guarantee a thread-safe implementation.
By replacing std::cout
with caf::aout
, actors can achieve a
concurrency-safe text output. The header caf/all.hpp
also defines overloads
for std::endl
and std::flush
for aout
, but does not support the full
range of ostream operations (yet). Each write operation to aout
sends a
message to a “hidden” actor. This actor only prints lines, unless output is
forced using flush
. The example below illustrates printing of lines of text
from multiple actors (in random order).