[libc] Fix WrapperGen seeing no arguments as a void argument.

[michaelrj]

Summary

This corrects WrapperGen generating incorrect wrappers for functions
that take no arguments. Previously it would generate a wrapper with a
single argument of type void.

[sivachandra]

libc/utils/tools/WrapperGen/Main.cpp

51

May be check that the ArgsList.size() is zero? If zero, break out of the for loop, else report a descriptive error?

[michaelrj]

change continue to break

[michaelrj]

submit comments

libc/utils/tools/WrapperGen/Main.cpp

51

ArgsList.size() is still 1 if there are no arguments, that's where the argument of type void is coming from. If ArgsList.size() was ever 0 it wouldn't even enter the for loop, as that's the check at the top. I did change the continue to a break though.

[sivachandra]

libc/utils/tools/WrapperGen/Main.cpp

51

Sorry! I intended to say, when you find a void arg type, check that ArgsList.size() == 1. If not, report a descriptive error.

[michaelrj]

add check for a void argument as well as other arguments in the same function.

[michaelrj]

submit comments

[sivachandra]

libc/utils/tools/WrapperGen/Main.cpp

60

Say something like,

"The specification for function " + FunctionName + " lists other arguments along with a void argument."

Pointing out that the specification is at fault tells the user where to go look.

[michaelrj]

make error message more helpful

[michaelrj]

submit messages (I really gotta remember to mark these before I run the arc command)

libc/utils/tools/WrapperGen/Main.cpp

OS << "extern \"C\" " << Indexer.getTypeAsString(ReturnType) << " "
      << FunctionName << "(";
 
   auto ArgsList = FunctionSpec->getValueAsListOfDefs("Args");
   std::stringstream CallArgs;
   std::string ArgPrefix("__arg");
   for (size_t i = 0; i < ArgsList.size(); ++i) {
     llvm::Record *ArgType = ArgsList[i]->getValueAsDef("ArgType");
     auto TypeName = Indexer.getTypeAsString(ArgType);
+
+    if (TypeName.compare("void") == 0) {
+      if (ArgsList.size() == 1) {
+        break;
+      } else {
+        // the reason this is a fatal error is that a void argument means this
+        // function has no arguments; multiple copies of no arguments is an
+        // error.
+        llvm::PrintFatalError(
+            "The specification for function " + FunctionName +
+            " lists other arguments along with a void argument.");
+      }
+    }
+
     OS << TypeName << " " << ArgPrefix << i;
     CallArgs << ArgPrefix << i;
     if (i < ArgsList.size() - 1) {
       OS << ", ";
       CallArgs << ", ";
     }
   }