If you think that's horrifying, what if I told you that a sufficiently-entitled operator of a given program can alter the flags at runtime ... using their web browser. https://twitter.com/jbeda/status/888635505201471490
Oh my. I have a gut feeling that I don't like it one bit, though I tend to be a bit more generous on logging. Logging is one of the only cases where its presence or absence don't change the inputs or outputs of any function, nor any other observable effect of the program. Having or removing logs doesn't impact the testability of a function, unlike any other use of global configuration.
You seem like a pretty reasonable person so prepare to be more shocked :-) In a glog stream like this, the things on the right side are not evaluated unless verbosity is on.
I have on occasion been called a reasonable person, and good heavens! I could understand that in a functional language with lazy evaluation, but that doesn't fit at all with my mental model of how C++ works. It can't be a macro, because the VLOG parentheses would need to enclose the entire expression. It can't just be the normal operator<< , because then the expression would always be evaluated. I suppose expression_with_side_effects() could return an object that is implicitly convertible to string, and the actual side effects happen in that optional conversion, but that would require lots of cooperation from the user.
I'm almost scared to ask. How is that even implemented?
