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A quick test shows neither -Wall nor -Wextra report anything on either gcc or clang. However, clang's -Weverything does complain (it implies -Wunreachable-code).

Confusingly, gcc accepts -Wunreachable-code as a valid option, but then proceeds not to warn anything. (edit): Which is a known bug apparently,

http://gcc.gnu.org/ml/gcc-help/2011-05/msg00360.html




The real WTF is those Warn flags, then. In what sane world does "extra" mean more than "all", and "all" and "everything" mean different things?


Excessive fear of backwards compatibility: you make -Wall. People use it. You add a new check which will reject some shoddy code. “What if people complain that their project no longer builds with -Wall? Let's add a new setting…”. Repeat…

I've been wondering how hard it would be to get to the point where the defaults are rigorous and developers have to opt out with specific -Wno-… options.


"-Wall" actually means, "all warnings, as of the date we froze the definition of -Wall, which for all you know was 20 years ago, good luck."


Apple introduced -Weverything because suddenly changing the scope of gcc's -Wall (which indeed does not include everything) would break a lot of builds.


Is "-Weverything" inclusive of new warnings? Because they're just kicking the can if not. What's next, "-Wreallyeverything"?


Yep. Even ones that may not be fully baked, so some people caution against it.

We have it turned on, and about 10 warnings specifically disabled because they were too noisy or not useful for us. It's always interesting upgrading Xcode and seeing what new warnings we get to fix.


"suddenly" is a funny way to say "over a span of years"....


Microsoft VC++ has a -Wall warning level too, and it really does mean all warnings. Each major version of VC++ potentially introduces new warnings to -Wall.


My personal observation is that while compilers continually get better at identifying straightforward mistakes, they don't have the same capability as a static analysis tool that works across compilation units. That is the real selling point of these tools. Definitely -Weverything/-Wexta plus static analysis for baseline checking.

My other beef is that compilers always add new warnings as options or behind new "catch all" flags like -Weverything that no one knows about. As long as each new warning can be individually disabled, there isn't a huge cost to pay by making much more of them enabled by default. Upgrading to a new compiler version usually requires a tiny bit of work, so adding a few -Wno-* rules for new things you want to disable until the code is clean (or forever) is a small price to pay for all new code getting the checks by default.




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