At the moment every `LOG()` macro invocation results in a `LogMessage` being
created, the message serialized into an `std::stringstream`. Only in the
destructor is it actually checked whether the given `LogCategory` enables
the given log level.
This is not too efficient, it would be better to skip the log message
construction and all the `operator<<()` invocations if the message will
just be discarded.
This could be easily done if the `LOG()` macro accepted its arguments like a
traditional function as in that case an appropriate `if` statement can be
injected in a do-while loop. However, that is not the case, the `LOG()` macro
should effectively "return" a stream.
It is not possible inject an `if` statement directly as that would
lead to issues:
if (...)
LOG(...)
else
...
The `else` would bind the to the `if` in the `LOG()` macro. This is
diagnosed by `-Wdangling-else`.
An alternative approach would be to use a `for` loop and force a single
iteration using a boolean flag or similar. This is entirely doable but
I think the implemented approach is easier to understand.
This change implements the early log level checking using a `switch` statement
as this avoids the dangling else related issues. One small issue arises
because having a boolean controlling expression is diagnosed by clang
(`-Wswitch-bool`); the result is cast to `int` to avoid the warning.
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
7d5321ac52