well, clearly not "maximum warnings" since you are missing a lot of them. -pedantic -Wunreachable-code -Wcast-qual -Wswitch-default -Wconversion -Wshadow -Wstrict-aliasing -Winit-self -Wcast-align -Wpointer-arith -Wmissing-declarations -Wmissing-include-dirs -Wno-unused-parameter -Wuninitialized and thats not even all that are useful.

Also, don't use -Werror if you can Warnings will change based on compiler, compiler version and a countless number of other factors that make working with code that turns them into errors a pain.