Clang-cl treats -Wall as -Weverything

[davidavetyan]

When passing the -Wall option to clang-cl options, all diagnostics are being reported. This would be the expected behavior for /Wall which enables -Weverything, but not for -Wall.

From the clang-cl user manual https://clang.llvm.org/docs/UsersManual.html#clang-cl:

  /Wall                   Enable -Weverything
  ...
  -W<warning>             Enable the specified warning

Used LLVM version 17.0.6

[adalisk-emikhaylov]

I believe this is intended, because cl.exe itself accepts options with both / and -,

[davidavetyan]

Ok, so I guess this is required for compatibility.
It'd be good to update the documentation to be clear about this, because the other warnings work as usual with '-'.

[efriedma-quic]

Yes, this is the way MSVC-style command-line parsing works. If you want the clang -Wall, you can pass /clang:-Wall