Add translation rules for variadic libc calls

cpp2rust/converter/converter.cpp

@@ -1447,6 +1447,13 @@ bool Converter::VisitCallExpr(clang::CallExpr *expr) {
   }
 
   if (Mapper::Contains(expr->getCallee())) {
+    if (auto tgt_ir = Mapper::GetExprRule(GetCalleeOrExpr(expr))) {
+      if (tgt_ir->body.empty() && tgt_ir->is_variadic) {
+        ConvertGenericCallExpr(expr);
+        return false;
+      }
+    }
+
     auto **args = expr->getArgs();
     auto num_args = expr->getNumArgs();
     auto ctx = CollectPrvalueToLRefArgs(expr);
@@ -1517,125 +1524,173 @@ void Converter::ConvertFunctionToFunctionPointer(
   StrCat(std::format("Some({})", Mapper::MapFunctionName(fn_decl)));
 }
 
-void Converter::ConvertGenericCallExpr(clang::CallExpr *expr) {
-  clang::Expr *callee = expr->getCallee();
-  auto convert_param_ty = [&](clang::QualType param_type, clang::Expr *expr) {
-    if (param_type->isLValueReferenceType()) {
-      PushExprKind push(*this, ExprKind::AddrOf);
-      ConvertVarInit(param_type, expr);
-    } else {
-      ConvertVarInit(param_type, expr);
-    }
-  };
+Converter::CallInfo Converter::CollectCallInfo(clang::CallExpr *expr) {
+  using Kind = CallArg::Kind;
 
-  unsigned arg_begin = 0; // skip count for operator()'s implicit object arg
+  CallInfo info;
+  info.expr = expr;
+  auto callee = GetCallee(expr);
+  unsigned arg_begin = 0;
   if (auto op_call = llvm::dyn_cast<clang::CXXOperatorCallExpr>(expr)) {
     if (op_call->getOperator() == clang::OO_Call) {
-      callee = op_call->getArg(0);
       arg_begin = 1;
     }
   }
 
-  PushParen outer(*this);
-  StrCat(keyword_unsafe_);
-  PushBrace unsafe_brace(*this);
-  const auto *function =
-      expr->getCalleeDecl() ? expr->getCalleeDecl()->getAsFunction() : nullptr;
+  auto decl = expr->getCalleeDecl();
+  const auto *function = decl ? decl->getAsFunction() : nullptr;
   const clang::FunctionProtoType *proto = nullptr;
-
   if (!function) {
     auto callee_ty = callee->getType().getDesugaredType(ctx_);
     if (auto ptr_ty = callee_ty->getAs<clang::PointerType>()) {
       proto = ptr_ty->getPointeeType()->getAs<clang::FunctionProtoType>();
     }
   }
-
   assert((function || proto) &&
          "Either function decl or function prototype should be known");
 
-  auto num_args = expr->getNumArgs() - arg_begin;
-  bool is_variadic =
-      function ? function->isVariadic() : (proto && proto->isVariadic());
-  unsigned num_named_params = function
-                                  ? function->getNumParams()
-                                  : (proto ? proto->getNumParams() : num_args);
-
-  // Track which args are materialized temps bound to reference params
-  std::vector<std::string> temp_refs(num_args);
+  unsigned num_args = expr->getNumArgs() - arg_begin;
+  unsigned num_named_params =
+      function ? function->getNumParams() : proto->getNumParams();
+  info.is_variadic = function ? function->isVariadic() : proto->isVariadic();
+  info.is_fn_ptr_call = !function;
+  info.is_libc_passthrough =
+      decl && ctx_.getSourceManager().isInSystemHeader(decl->getLocation());
 
   for (unsigned i = 0; i < num_named_params && i < num_args; ++i) {
     auto *arg = expr->getArg(i + arg_begin);
-    std::string param_name = function
-                                 ? function->getParamDecl(i)->getNameAsString()
-                                 : ("arg" + std::to_string(i));
-    clang::QualType param_type = function ? function->getParamDecl(i)->getType()
-                                          : proto->getParamType(i);
+    CallArg ca{
+        .param_name = function
+                          ? ("_" + function->getParamDecl(i)->getNameAsString())
+                          : ("_arg" + std::to_string(i)),
+        .param_type = function ? function->getParamDecl(i)->getType()
+                               : proto->getParamType(i),
+        .expr = arg,
+        .has_default = function && function->getParamDecl(i)->hasDefaultArg(),
+        .kind = info.is_libc_passthrough ? Kind::Inline : Kind::Hoisted,
+    };
+    bool is_materialize = clang::isa<clang::MaterializeTemporaryExpr>(arg);
+    if (is_materialize && ca.param_type->isLValueReferenceType()) {
+      ca.kind = Kind::Materialized;
+    } else if (is_materialize) {
+      ca.kind = Kind::Inline;
+    }
+    info.args.push_back(std::move(ca));
+  }
 
-    bool is_materialize_to_ref =
-        clang::isa<clang::MaterializeTemporaryExpr>(arg) &&
-        param_type->isLValueReferenceType();
+  if (info.is_variadic) {
+    for (unsigned i = num_named_params; i < num_args; ++i) {
+      info.variadic_args.push_back(expr->getArg(i + arg_begin));
+    }
+  }
+
+  return info;
+}
 
-    if (is_materialize_to_ref) {
+void Converter::ConvertParamTy(clang::QualType param_type, clang::Expr *expr) {
+  if (param_type->isLValueReferenceType()) {
+    PushExprKind push(*this, ExprKind::AddrOf);
+    ConvertVarInit(param_type, expr);
+  } else {
+    ConvertVarInit(param_type, expr);
+  }
+}
+
+void Converter::EmitHoistedArgs(CallInfo &info) {
+  using Kind = CallArg::Kind;
+  for (auto &ca : info.args) {
+    switch (ca.kind) {
+    case Kind::Hoisted:
+      StrCat(
+          std::format("let {}: {} =", ca.param_name, ToString(ca.param_type)));
+      ConvertParamTy(ca.param_type, ca.expr);
+      StrCat(";");
+      break;
+    case Kind::Materialized: {
       auto [binding, ref] =
-          MaterializeTemp(std::format("_{}", param_name), param_type, arg);
+          MaterializeTemp(ca.param_name, ca.param_type, ca.expr);
       StrCat(binding);
-      temp_refs[i] = std::move(ref);
-    } else if (!clang::isa<clang::MaterializeTemporaryExpr>(arg)) {
-      StrCat("let", std::format("_{}: {}", param_name, ToString(param_type)),
-             "=");
-      convert_param_ty(param_type, arg);
-      StrCat(";");
+      ca.ref_temp_name = std::move(ref);
+      break;
+    }
+    case Kind::Inline:
+      break;
     }
   }
+}
 
-  if (proto && !function) {
-    EmitFnPtrCall(callee);
-  } else {
-    PushExprKind push(*this, ExprKind::Callee);
-    Convert(callee);
-  }
-  {
-    PushParen call_args(*this);
-    for (unsigned i = 0; i < num_named_params && i < num_args; ++i) {
-      auto *arg = expr->getArg(i + arg_begin);
-      std::string param_name =
-          function ? function->getParamDecl(i)->getNameAsString()
-                   : ("arg" + std::to_string(i));
-      clang::QualType param_type = function
-                                       ? function->getParamDecl(i)->getType()
-                                       : proto->getParamType(i);
-      bool is_parm_with_default_value =
-          function && function->getParamDecl(i)->hasDefaultArg();
-
-      if (is_parm_with_default_value) {
-        StrCat("Some(");
-      }
-      if (!temp_refs[i].empty()) {
-        StrCat(temp_refs[i]);
-      } else if (clang::isa<clang::MaterializeTemporaryExpr>(arg)) {
-        convert_param_ty(param_type, arg);
-      } else {
-        StrCat(std::format("_{}", param_name));
-      }
-      if (is_parm_with_default_value) {
-        StrCat(')');
+void Converter::EmitArgList(const CallInfo &info) {
+  using Kind = CallArg::Kind;
+  PushParen call_args(*this);
+
+  for (unsigned i = 0; i < info.args.size(); i++) {
+    const auto &ca = info.args[i];
+
+    if (ca.has_default) {
+      StrCat("Some");
+    }
+
+    {
+      PushParen push(*this, ca.has_default);
+      switch (ca.kind) {
+      case Kind::Hoisted:
+        StrCat(ca.param_name);
+        break;
+      case Kind::Materialized:
+        StrCat(ca.ref_temp_name);
+        break;
+      case Kind::Inline:
+        ConvertParamTy(ca.param_type, ca.expr);
+        if (info.is_libc_passthrough) {
+          StrCat(std::format(
+              "as {}", Mapper::GetParamType(GetCalleeOrExpr(info.expr), i)));
+        }
+        break;
       }
-      StrCat(token::kComma);
     }
 
-    // Variadic args: wrap in &[arg.into(), ...]
-    if (is_variadic) {
-      StrCat("& [");
-      for (unsigned i = num_named_params; i < num_args; ++i) {
-        auto *arg = expr->getArg(i + arg_begin);
-        ConvertVariadicArg(arg);
-        StrCat(".into()", token::kComma);
+    StrCat(token::kComma);
+  }
+
+  if (info.is_variadic) {
+    if (!info.is_libc_passthrough) {
+      StrCat(token::kRef);
+    }
+    PushBracket push(*this, !info.is_libc_passthrough);
+    for (auto *arg : info.variadic_args) {
+      ConvertVariadicArg(arg);
+      if (!info.is_libc_passthrough) {
+        StrCat(".into()");
       }
-      StrCat(']');
+      StrCat(token::kComma);
     }
   }
 }
 
+void Converter::EmitCall(CallInfo &&info) {
+  EmitHoistedArgs(info);
+
+  if (info.is_fn_ptr_call) {
+    EmitFnPtrCall(GetCallee(info.expr));
+  } else if (info.is_libc_passthrough) {
+    auto *direct_callee = info.expr->getDirectCallee();
+    assert(direct_callee);
+    StrCat("libc::", direct_callee->getName());
+  } else {
+    PushExprKind push(*this, ExprKind::Callee);
+    Convert(GetCallee(info.expr));
+  }
+
+  EmitArgList(info);
+}
+
+void Converter::ConvertGenericCallExpr(clang::CallExpr *expr) {
+  PushParen outer(*this);
+  StrCat(keyword_unsafe_);
+  PushBrace unsafe_brace(*this);
+  EmitCall(CollectCallInfo(expr));
+}
+
 std::optional<Converter::TempMaterializationCtx>
 Converter::ConvertCallExpr(clang::CallExpr *expr) {
   auto *callee = expr->getCallee();

cpp2rust/converter/converter.h

@@ -219,6 +219,40 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   std::optional<TempMaterializationCtx> ConvertCallExpr(clang::CallExpr *expr);
 
+  struct CallArg {
+    enum class Kind : int8_t {
+      Hoisted,
+      Inline,
+      Materialized,
+    };
+
+    std::string param_name;
+    std::string ref_temp_name;
+    clang::QualType param_type;
+    clang::Expr *expr;
+    bool has_default;
+    Kind kind;
+  };
+
+  struct CallInfo {
+    std::vector<CallArg> args;
+    std::vector<clang::Expr *> variadic_args;
+    clang::CallExpr *expr;
+    bool is_variadic;
+    bool is_fn_ptr_call;
+    bool is_libc_passthrough;
+  };
+
+  CallInfo CollectCallInfo(clang::CallExpr *expr);
+
+  void ConvertParamTy(clang::QualType param_type, clang::Expr *expr);
+
+  void EmitHoistedArgs(CallInfo &info);
+
+  void EmitArgList(const CallInfo &info);
+
+  void EmitCall(CallInfo &&info);
+
   void ConvertGenericCallExpr(clang::CallExpr *expr);
 
   virtual void EmitFnPtrCall(clang::Expr *callee);

cpp2rust/converter/converter_lib.cpp

@@ -588,6 +588,15 @@ BuildUnifiedArgs(clang::Expr *expr, clang::Expr **args, unsigned num_args) {
   return all_args;
 }
 
+clang::Expr *GetCallee(clang::CallExpr *expr) {
+  if (auto op_call = clang::dyn_cast<clang::CXXOperatorCallExpr>(expr)) {
+    if (op_call->getOperator() == clang::OO_Call) {
+      return op_call->getArg(0);
+    }
+  }
+  return expr->getCallee();
+}
+
 clang::Expr *GetCalleeOrExpr(clang::Expr *expr) {
   if (auto *call = clang::dyn_cast<clang::CallExpr>(expr)) {
     return call->getCallee();

cpp2rust/converter/converter_lib.h

@@ -129,6 +129,8 @@ void ForEachTemplateArgument(
 
 clang::Expr *GetCallObject(clang::CallExpr *expr);
 
+clang::Expr *GetCallee(clang::CallExpr *expr);
+
 clang::Expr *GetCalleeOrExpr(clang::Expr *expr);
 
 bool HasReceiver(clang::Expr *expr);

cpp2rust/converter/mapper.cpp

@@ -792,6 +792,12 @@ std::string ToString(const clang::NamedDecl *decl) {
     }
     os << ToString(func_decl->getParamDecl(i)->getType());
   }
+  if (func_decl->isVariadic()) {
+    if (func_decl->getNumParams()) {
+      os << ", ";
+    }
+    os << "...";
+  }
   os << ')';
 
   if (const auto *method_decl =

cpp2rust/converter/translation_rule.cpp

@@ -104,6 +104,9 @@ ExprRule ParseExprRuleJSON(const llvm::json::Object &obj) {
   if (auto ms = obj.getBoolean("multi_statement"))
     ir.multi_statement = *ms;
 
+  if (auto v = obj.getBoolean("is_variadic"))
+    ir.is_variadic = *v;
+
   if (auto *generics = obj.getObject("generics")) {
     for (auto &[key, val] : *generics) {
       if (auto *arr = val.getAsArray()) {

cpp2rust/converter/translation_rule.h

@@ -70,6 +70,7 @@ struct ExprRule {
   std::vector<std::vector<std::string>> generics; // "T1" -> ["Ord", "Clone"]
   std::vector<BodyFragment> body;
   bool multi_statement = false;
+  bool is_variadic = false;
 
   void dump() const;
   void validate(const std::string &name) const;