This macro is enabled when the SDL_ASSERT_LEVEL
is >= 2, otherwise it is disabled. This is meant to only do these tests in debug builds, so they can
tend to be more expensive, and they are meant to bring everything to a halt when they fail, with the
programmer there to assess the problem.
In short: you can sprinkle these around liberally and assume they will evaporate out of the build when
building for end-users.
When assertions are disabled, this wraps condition in a sizeof operator, which means any function calls
and side effects will not run, but the compiler will not complain about any otherwise-unused variables
that are only referenced in the assertion.
One can set the environment variable " SDL_ASSERT " to one of several strings ("abort", "break", "retry",
"ignore", "always_ignore") to force a default behavior, which may be desirable for automation purposes.
If your platform requires GUI interfaces to happen on the main thread but you're debugging an assertion
in a background thread, it might be desirable to set this to "break" so that your debugger takes control
as soon as assert is triggered, instead of risking a bad UI interaction (deadlock, etc) in the
application.