Option parsing: properly handle flag aliases for joined options (PR23394)

A joined option always needs to have an argument, even if it's an empty one.

Clang would previously assert when trying to use --extra-warnings, which is
a flag alias for -W, which is a joined option.

llvm-svn: 236434

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Option/Option.cpp b/llvm/lib/Option/Option.cpp
index e29d6491c7f..221414d79e7 100644
--- a/llvm/lib/Option/Option.cpp
+++ b/llvm/lib/Option/Option.cpp
@@ -125,6 +125,11 @@ Arg *Option::accept(const ArgList &Args,
         Val += strlen(Val) + 1;
       }
     }
+
+    if (UnaliasedOption.getKind() == JoinedClass && !getAliasArgs())
+      // A Flag alias for a Joined option must provide an argument.
+      A->getValues().push_back("");
+
     return A;
   }
   case JoinedClass: {