-WallIf you read that as "wall" then it's not too misleading, but it is kind of meaningless. If you read it as "Warnings all" it seems meaningful but it's really misleading. –Wmost would have been better, although I'm not sure if even that is accurate. I turn on –Wall and feel pretty smug when I compile without warnings. The smugness, it turns out, is unwarranted. If you want to get closer to all add –Wextra. The specific dozen or so checks that are added are defined in the warning options docs.
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For an extra dose of humility you can also add the -Weffc++ warning. The latter is defined in the dialect options docs. I have no idea why this is here rather than in the warnings documentation. I would have never found it except I was interested in reading what Scott Meyer's felt were the most important C++ books, and he mentioned it. This option adds warning for violations 0f items 11, 12, 14,15 and 23 of his Effective C++ and items 6 &7 of More Effective C++.
Unfortunately, for either setting there is no way to turn off warnings for files from certain locations (like libraries). Many files I don't have control over will not cleanly pass. However, it's easy to separate those from the ones you care about. The path column is empty for the system libraries, and a path you should recognize will be present for your code as shown in the image.