Among the numerous GCC 6 features to have been built up over the past year was the new -Wmisleading-indentation warning. This warning will notify you when it appears there is code that wasn't indented properly and so may not match the intended logic of the developer.
This new warning isn't enabled by default. If you wish to learn more about -Wmisleading-indentation option, see this documentation commit.
This option has been supported in the GCC SVN/Git code for some months already while GCC 6 is set to be officially released with this and many other features around March. One of the first major Linux distributions expected to ship with GCC 6 is Fedora 24.