2 files changed, 16 insertions, 7 deletions
diff --git a/src/support/command-line.cpp b/src/support/command-line.cpp
index 0e638173e..1b9f64295 100644
--- a/src/support/command-line.cpp
+++ b/src/support/command-line.cpp
@@ -136,11 +136,13 @@ void Options::parse(int argc, const char* argv[]) {
       // Positional.
       switch (positional) {
         case Arguments::Zero:
+          // Optional arguments must use --flag=A format, and not separated by
+          // spaces (which would be ambiguous).
+        case Arguments::Optional:
           std::cerr << "Unexpected positional argument '" << currentOption
                     << "'\n";
           exit(EXIT_FAILURE);
         case Arguments::One:
-        case Arguments::Optional:
           if (positionalsSeen) {
             std::cerr << "Unexpected second positional argument '"
                       << currentOption << "' for " << positionalName << '\n';
@@ -198,11 +200,6 @@ void Options::parse(int argc, const char* argv[]) {
         }
         break;
       case Arguments::Optional:
-        if (!argument.size()) {
-          if (i + 1 != e) {
-            argument = argv[++i];
-          }
-        }
         break;
     }
     option->action(this, argument);
diff --git a/src/support/command-line.h b/src/support/command-line.h
index 53bdbff28..99d98eec9 100644
--- a/src/support/command-line.h
+++ b/src/support/command-line.h
@@ -34,7 +34,19 @@ namespace wasm {
 class Options {
 public:
   using Action = std::function<void(Options*, const std::string&)>;
-  enum class Arguments { Zero, One, N, Optional };
+
+  enum class Arguments {
+    // No arguments.
+    Zero,
+    // One argument, in the form  --flag A  or  --flag=A
+    One,
+    // Multiple arguments, in the form --flag A B C
+    N,
+    // An optional single argument, in the form --flag=A (we disallow --flag A
+    // as that would be ambiguous regarding whether A is another flag, or an
+    // argument to us).
+    Optional
+  };
 
   bool debug;
   std::map<std::string, std::string> extra;