diff --git a/cl/compile.go b/cl/compile.go
index 3a4fd9fa..e6a5ed3d 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -387,6 +387,9 @@ func (p *context) compileInstr(b llssa.Builder, instr ssa.Instruction) {
 		thenb := fn.Block(succs[0].Index)
 		elseb := fn.Block(succs[1].Index)
 		b.If(cond, thenb, elseb)
+	case *ssa.Panic:
+		arg := p.compileValue(b, v.X).Do()
+		b.Panic(arg)
 	default:
 		panic(fmt.Sprintf("compileInstr: unknown instr - %T\n", instr))
 	}
diff --git a/internal/runtime/z_slice.go b/internal/runtime/z_slice.go
index b6d5cbf5..a3f59f6d 100644
--- a/internal/runtime/z_slice.go
+++ b/internal/runtime/z_slice.go
@@ -16,8 +16,10 @@
 
 package runtime
 
+// Slice is the runtime representation of a slice.
 type Slice = slice
 
-func MakeEmptySlice() Slice {
+// NilSlice returns a nil slice.
+func NilSlice() Slice {
 	return Slice{nil, 0, 0}
 }
diff --git a/internal/runtime/z_string.go b/internal/runtime/z_string.go
new file mode 100644
index 00000000..ed8ca0c1
--- /dev/null
+++ b/internal/runtime/z_string.go
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+// String is the runtime representation of a string.
+// It cannot be used safely or portably and its representation may
+// change in a later release.
+//
+// Unlike reflect.StringHeader, its Data field is sufficient to guarantee the
+// data it references will not be garbage collected.
+type String struct {
+	data unsafe.Pointer
+	len  int
+}
+
+// EmptyString returns an empty string.
+func EmptyString() String {
+	return String{nil, 0}
+}
diff --git a/ssa/expr.go b/ssa/expr.go
index eda2c4dc..b1a2fe54 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -82,6 +82,20 @@ func (p Program) Null(t Type) Expr {
 	return Expr{llvm.ConstNull(t.ll), t}
 }
 
+// CStringVal returns a c-style string constant expression.
+func (p Program) CStringVal(v string) Expr {
+	t := p.CString()
+	return Expr{llvm.ConstString(v, true), t}
+}
+
+// StringVal returns string constant expression.
+func (p Program) StringVal(v string) Expr {
+	t := p.String()
+	cstr := llvm.ConstString(v, true)
+	// TODO(xsw): cstr => gostring
+	return Expr{cstr, t}
+}
+
 // BoolVal returns a boolean constant expression.
 func (p Program) BoolVal(v bool) Expr {
 	t := p.Bool()
@@ -118,19 +132,22 @@ func (p Program) Val(v interface{}) Expr {
 
 // Const returns a constant expression.
 func (b Builder) Const(v constant.Value, typ Type) Expr {
+	prog := b.prog
 	if v == nil {
-		return b.prog.Null(typ)
+		return prog.Null(typ)
 	}
 	switch t := typ.t.(type) {
 	case *types.Basic:
 		kind := t.Kind()
 		switch {
 		case kind == types.Bool:
-			return b.prog.BoolVal(constant.BoolVal(v))
+			return prog.BoolVal(constant.BoolVal(v))
 		case kind >= types.Int && kind <= types.Uintptr:
 			if v, exact := constant.Uint64Val(v); exact {
-				return b.prog.IntVal(v, typ)
+				return prog.IntVal(v, typ)
 			}
+		case kind == types.String:
+			return prog.StringVal(constant.StringVal(v))
 		}
 	}
 	panic("todo")
diff --git a/ssa/package.go b/ssa/package.go
index cd63b986..edddc5c6 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -110,12 +110,15 @@ type aProgram struct {
 	voidType  llvm.Type
 	voidPtrTy llvm.Type
 
-	rtIfaceTy llvm.Type
-	rtSliceTy llvm.Type
+	rtStringTy llvm.Type
+	rtIfaceTy  llvm.Type
+	rtSliceTy  llvm.Type
 
 	anyTy     Type
 	voidTy    Type
 	boolTy    Type
+	cstrTy    Type
+	stringTy  Type
 	uintptrTy Type
 	intTy     Type
 	f64Ty     Type
@@ -170,6 +173,13 @@ func (p Program) rtSlice() llvm.Type {
 	return p.rtSliceTy
 }
 
+func (p Program) rtString() llvm.Type {
+	if p.rtStringTy.IsNil() {
+		p.rtStringTy = p.rtType("String").ll
+	}
+	return p.rtStringTy
+}
+
 // NewPackage creates a new package.
 func (p Program) NewPackage(name, pkgPath string) Package {
 	mod := p.ctx.NewModule(pkgPath)
@@ -177,7 +187,7 @@ func (p Program) NewPackage(name, pkgPath string) Package {
 	// mod.Finalize()
 	fns := make(map[string]Function)
 	gbls := make(map[string]Global)
-	return &aPackage{mod, fns, gbls, p}
+	return &aPackage{mod, fns, gbls, p, nil}
 }
 
 // Void returns void type.
@@ -196,6 +206,20 @@ func (p Program) Bool() Type {
 	return p.boolTy
 }
 
+func (p Program) CString() Type {
+	if p.cstrTy == nil { // *int8
+		p.cstrTy = p.Type(types.NewPointer(types.Typ[types.Int8]))
+	}
+	return p.cstrTy
+}
+
+func (p Program) String() Type {
+	if p.stringTy == nil {
+		p.stringTy = p.Type(types.Typ[types.String])
+	}
+	return p.stringTy
+}
+
 // Any returns any type.
 func (p Program) Any() Type {
 	if p.anyTy == nil {
@@ -243,6 +267,8 @@ type aPackage struct {
 	fns  map[string]Function
 	vars map[string]Global
 	prog Program
+
+	abort Function
 }
 
 type Package = *aPackage
@@ -280,6 +306,13 @@ func (p Package) FuncOf(name string) Function {
 	return p.fns[name]
 }
 
+func (p Package) rtAbort() Function {
+	if p.abort == nil {
+		p.abort = p.NewFunc("abort", types.NewSignatureType(nil, nil, nil, nil, nil, false))
+	}
+	return p.abort
+}
+
 func (p Package) rtFunc(fnName string) Expr {
 	fn := p.prog.runtime().Lookup(fnName).(*types.Func)
 	name := FullName(fn.Pkg(), fnName)
diff --git a/ssa/stmt_builder.go b/ssa/stmt_builder.go
index a5e2f1f2..9b165cfb 100644
--- a/ssa/stmt_builder.go
+++ b/ssa/stmt_builder.go
@@ -68,6 +68,15 @@ func (b Builder) SetBlock(blk BasicBlock) Builder {
 	return b
 }
 
+// Panic emits a panic instruction.
+func (b Builder) Panic(v Expr) {
+	if debugInstr {
+		log.Printf("Panic %v\n", v.impl)
+	}
+	pkg := b.fn.pkg
+	b.Call(pkg.rtAbort().Expr)
+}
+
 // Return emits a return instruction.
 func (b Builder) Return(results ...Expr) {
 	if debugInstr {
diff --git a/ssa/type.go b/ssa/type.go
index dc5d20aa..fed294c7 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -237,6 +237,7 @@ func (p Program) toLLVMType(typ types.Type) Type {
 		case types.Complex64:
 		case types.Complex128:
 		case types.String:
+			return &aType{p.rtString(), typ, vkString}
 		case types.UnsafePointer:
 			return &aType{p.tyVoidPtr(), typ, vkPtr}
 		}