this post was submitted on 21 Nov 2023
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A simple
if (false)will get optimized out by any modern C or C++ compiler with optimizations on, but the problem is that the compiler will still parse and spend time on what's inside the if-block and it has to be legal code, whereas with the#if 0trick the whole thing gets yeeted away by the preprocessor before even the compiler gets to look at it regardless of whether that block contains errors or not, it's literally just a string manipulation.I think you missed the whole point of my comment ๐. Regardless, the time spent compiling a small snippet of code is completely negligible. In the end, both
#if 0andif (false)have their complimentary uses.Yeah, but I still think
if (false)is silly because it adds an artificial constraint which is to make sure the disabled parts always compile even when you're not using them. The equivalent of that would be having to check that all the revisions of a single source file compile against your current codebase.If(false) works in interpreted languages, the other one doesn't. It's stupid either way, that's what version control is for, but if we are doing the stupidness anyway, you can't use preprocessor flags in many languages because shit doesn't get compiled.