Josh Rosenberg <[email protected]> added the comment:
Gregory: Even in a low-level compiled language (say, C++), pretty sure the
compiler can't automatically optimize out:
if (x) { }
unless it has sure knowledge of the implementation of operator bool; if
operator bool's implementation isn't in the header file, and link time
optimization isn't involved, it has to call it to ensure any side-effects it
might have are invoked.
It can only bypass the call if it knows the implementation of operator bool and
can verify it has no observable side-effects (as-if rule). There are exceptions
to the as-if rule for optimizations in special cases (copy elision), but I'm
pretty sure operator bool isn't one of them; if the optimizer doesn't know the
implementation of operator bool, it must call it just in case it does something
weird but critical to the program logic.
Point is, I agree that:
if x:
pass
must evaluate non-constant-literal x for truthiness, no matter how silly that
seems (not a huge loss, given very little code should ever actually do that).
----------
nosy: +josh.r
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