[llvm-dev] [llvm-rc] absolute.test failing

[David Greene via llvm-dev]

I've come across a curious and pernicious problem in llvm-rc.
absolute.test checks that llvm-rc can accept a filename that is an
absolute path.  And it works just fine.  Until you run it with a file
that starts with "/c."

These will fail:

llvm-rc /crawl/through/some/path/to/my.rc
llvm-rc /c/some/path/to/my.rc

The option parser ends up interpreting "/" as an option prefix and then
the parser matches it to this in tools/llvm-rc/Opts.td:

def CODEPAGE : JoinedOrSeparate<[ "/", "-" ], "C">,
               HelpText<"Set the codepage used for input strings.">;

The test then fails with:
  Exactly one input file should be provided.

The same problem happens with files that begin with "/r"
(/read/the/path/to/my.rc) "/sl" (/slink/along/the/path/to/my.rc) or any
other path that happens to begin with the same text as an option in
Opts.td.

This triggered on one of our builders that just happens to build to a
path that begins with "/c."  Presumably none of the existing Buildbots
build to paths that cause problems.

It's easy enough to construct a test for this, but I'm not sure how/if
llvm-rc should be fixed.  I don't know why it accepts both "/" and "-"
as option prefixes.  As this mostly seems related to Windows (resource
files), should tests be UNSUPPORTED on every other platform?  Or is
llvm-rc intended to be a cross-platform way to create resource files?
If the latter, then it seems like options ought to use the "/" prefix on
Windows and "-" everywhere else so as not to conflict with path
specifiers.

                             -David