Enables warning and error diagnostics.
This option enables many warning and error diagnostics.
On Windows* systems, this option is equivalent to the /W4 option. It enables diagnostics for all level 3 warnings plus informational warnings and remarks.
However, on Linux* and OS X* systems, this option is similar to gcc option -Wall. It displays all errors and some of the warnings that are typically reported by gcc option -Wall. If you want to display all warnings, specify the -w2 or -w3 option. If you want to display remarks and comments, specify the -Wremarks option.
The Wall, -wn, and /Wn options can override each other. The last option specified on the command line takes precedence.