3.6.4.5 Wall Option

The -Wall option enables all the warnings about easily avoidable constructions that some users consider questionable, even in conjunction with macros.

Note that some warning flags are not implied by -Wall. Of these warnings, some relate to constructions that users generally do not consider questionable, but which you might occasionally wish to check. Others warn about constructions that are necessary or hard to avoid in some cases and there is no simple way to modify the code to suppress the warning. Some of these warnings can be enabled using the -Wextra option, but many of them must be enabled individually.