Geoff Chappell - Software Analyst
The option is /Wall only.
The /Wall option implies /W4.
This option passes to both the front-end and back-end compilers (C1, C1XX and C2).
Each compiler module has a set of warnings that it configures automatically, some disabled, some promoted to errors and some to show only once. The effect is as if corresponding /wd, /we or /wo options were generated internally, in advance of acting on options from the command line.
The /Wall option directs that the compilers omit the internal /wd options from this initial configuration. The affected warnings are listed in the notes for /wd.