feat(codegen): accept ^x of C values as variadic arguments

In a variadic EXTERN position, ^x now passes the address of x as a plain
pointer when x has a C type or is a C struct, like C's f(n, &x). The
address of a pseudocode-typed value keeps the "must be a C value" error.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/lib/CodeGen/CallGen.cc b/lib/CodeGen/CallGen.cc
index 576520d..4631332 100644
--- a/lib/CodeGen/CallGen.cc
+++ b/lib/CodeGen/CallGen.cc
@@ -133,7 +133,10 @@ bool CodeGen::marshalCallArgs(const FuncSig &Signature,
 // C structs and pointers to them pass unchanged (C11 6.5.2.2p6-7, 7.16.1.1p2).
 Value *CodeGen::emitVariadicArgument(ExprAST *Expr, const std::string &Callee, size_t Position,
                                      const TypeInfo *&Promoted) {
-    const TypeInfo *Info = isWholeArrayVar(Expr) ? nullptr : getExprTypeInfo(Expr);
+    ExprAST *Target = Expr;
+    auto *Addr = dynamic_cast<AddrOfExprAST *>(Expr);
+    if (Addr) Target = Addr->getTarget();
+    const TypeInfo *Info = isWholeArrayVar(Target) ? nullptr : getExprTypeInfo(Target);
     const TypeInfo *Record = Types->pointerBase(Info);
     std::string Why;
     if (Record && Record->isRecord() && !Record->IsClass && !Types->isCStruct(Record, &Why)) {
@@ -145,6 +148,13 @@ Value *CodeGen::emitVariadicArgument(ExprAST *Expr, const std::string &Callee, s
         reportError("Variadic argument %zu to %s must be a C value; cast it to a C type", Position, Callee.c_str());
         return nullptr;
     }
+    // ^x of a C value or C struct is a plain pointer, like C's f(n, &x).
+    if (Addr) {
+        LValueInfo LV;
+        if (!emitLValue(Target, LV)) return nullptr;
+        Promoted = Types->resolve("C_TYPE(\"void*\")");
+        return LV.Addr;
+    }
     Promoted = Info;
     Value *V = emitExpr(Expr);
     if (!V || Info->Kind != TypeKind::CScalar) return V;