diff --git a/build.gradle.kts b/build.gradle.kts
index 8201457..957492e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -56,6 +56,7 @@ dependencies {
   testImplementation("org.junit.jupiter:junit-jupiter:5.5.2")
   implementation("org.jetbrains.kotlin:kotlin-script-runtime:1.4.32")
   implementation("org.jetbrains.kotlin:kotlin-reflect:1.4.32")
+  implementation("com.github.jnr:jnr-posix:3.1.5")
 }
 
 java {
diff --git a/src/cbor.kt b/src/cbor.kt
index 3219094..d06e9d1 100644
--- a/src/cbor.kt
+++ b/src/cbor.kt
@@ -115,6 +115,7 @@ fun KClass<*>.isInline(): Boolean {
     java.declaredMethods.any { it.name == "box-impl" }
 }
 
+// TODO: use https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/ClassValue.html here?
 val argsMap: Cache<KType,Array<KType?>> = Cache { it.arguments.map { x -> x.type }.toTypedArray() }
 val paramsTypes: Cache<KCallable<*>, Array<KType>> = Cache { it.parameters.map { x -> x.type }.toTypedArray() }
 val isEnumMap: Cache<Class<*>, Boolean> = Cache { Enum::class.java.isAssignableFrom(it) }
diff --git a/src/trufflestg/data/AlgData.kt b/src/trufflestg/data/AlgData.kt
index d1dbac5..2913c0c 100644
--- a/src/trufflestg/data/AlgData.kt
+++ b/src/trufflestg/data/AlgData.kt
@@ -227,7 +227,7 @@ class DynamicClassDataConInfo(
       when (it) {
         klass.name -> klass
         else -> TODO(it)
-      }} as Class<DataFrameBuilder>
+      }}
     builderKlass.constructors[0].newInstance() as DataFrameBuilder
   }
 }
diff --git a/src/trufflestg/data/Closure.kt b/src/trufflestg/data/Closure.kt
index 1b78931..1ca1e98 100644
--- a/src/trufflestg/data/Closure.kt
+++ b/src/trufflestg/data/Closure.kt
@@ -22,6 +22,7 @@ import trufflestg.jit.IndirectCallerNode
 
 // TODO: selector thunks
 // TODO: could avoid array allocation on thunk invocation by storing array in Closure/mb having a ThunkClosure class?
+// TODO: once we have thunk forwarding could inline Closure into Thunk?
 class Thunk(
   @JvmField var clos: Closure?,
   @JvmField var value_: Any?
diff --git a/src/trufflestg/data/stg_data.kt b/src/trufflestg/data/stg_data.kt
index 864a5e2..f50c6d3 100644
--- a/src/trufflestg/data/stg_data.kt
+++ b/src/trufflestg/data/stg_data.kt
@@ -8,6 +8,7 @@ import org.intelligence.diagnostics.error
 import org.intelligence.pretty.Pretty
 import java.lang.ref.WeakReference
 import kotlin.reflect.KClass
+import java.nio.ByteBuffer
 
 // JvmField should make PE faster and might help graal
 
@@ -53,6 +54,7 @@ class StgAddr(
   operator fun set(ix: StgInt, y: Byte) { arr[offset + ix.x.toInt()] = y }
 
   fun asArray(): ByteArray = arr.copyOfRange(offset, arr.size)
+  fun asBuffer(): ByteBuffer = ByteBuffer.wrap(arr, offset, arr.size - offset)
 }
 
 // afaict this guy can be mutable (& freeze & unfreeze operate on it)?
@@ -67,6 +69,8 @@ class StgMutableByteArray(
   @JvmField val arr: ByteArray
 ) {
   @JvmField var frozen: Boolean = false
+
+  fun asBuffer(): ByteBuffer = ByteBuffer.wrap(arr)
 }
 
 //class StgByteArray(
@@ -106,6 +110,7 @@ class WeakRef(
 )
 
 // TODO: don't store these in closures & etc, only use them in functions, maybe ensureVirtualized
+// TODO: UnboxedTuple1 etc?
 @CompilerDirectives.ValueType
 class UnboxedTuple(
   @JvmField val x: Array<Any>
diff --git a/src/trufflestg/jit/StgFCall.kt b/src/trufflestg/jit/StgFCall.kt
index a6cb208..f8f559f 100644
--- a/src/trufflestg/jit/StgFCall.kt
+++ b/src/trufflestg/jit/StgFCall.kt
@@ -1,26 +1,20 @@
 package trufflestg.jit
 
 import com.oracle.truffle.api.CompilerDirectives
-import com.oracle.truffle.api.Truffle
-import com.oracle.truffle.api.TruffleLanguage
-import trufflestg.data.*
-import trufflestg.panic
-import trufflestg.stg.Stg
+import com.oracle.truffle.api.exception.AbstractTruffleException
 import com.oracle.truffle.api.frame.VirtualFrame
+import com.oracle.truffle.api.interop.ExceptionType
+import com.oracle.truffle.api.interop.InteropLibrary
+import com.oracle.truffle.api.library.ExportLibrary
+import com.oracle.truffle.api.library.ExportMessage
+import com.oracle.truffle.api.nodes.Node
 import trufflestg.Language
 import trufflestg.array_utils.*
-import java.nio.charset.StandardCharsets
+import trufflestg.data.*
+import trufflestg.panic
+import trufflestg.stg.Stg
 import java.security.MessageDigest
 
-object GlobalStore {
-  var GHCConcSignalSignalHandlerStore: Any? = null
-}
-
-
-val zeroBytes: ByteArray = byteArrayOf(0, 0, 0, 0, 0, 0, 0, 0)
-
-var globalHeap = ByteArray(0)
-
 class StgFCall(
   val x: Stg.ForeignCall,
   @field:Children val args: Array<Arg>
@@ -38,15 +32,25 @@ class StgFCall(
   }
 }
 
+fun ByteArray.asCString(): String = String(copyOfRange(0, indexOf(0x00)))
+val posix = jnr.posix.POSIXFactory.getPOSIX()
+val zeroBytes: ByteArray = byteArrayOf(0, 0, 0, 0, 0, 0, 0, 0)
 
-var md5: MessageDigest? = null
+@ExportLibrary(InteropLibrary::class)
+class TruffleStgExitException(val status: Int) : AbstractTruffleException() {
+  @ExportMessage fun getExceptionType(): ExceptionType = ExceptionType.EXIT
+  @ExportMessage fun getExceptionExitStatus(): Int = status
+}
 
-@CompilerDirectives.TruffleBoundary
-fun ByteArray.asCString(): String = String(copyOfRange(0, indexOf(0x00)))
+// mutable state
+var md5: MessageDigest? = null
+object GlobalStore {
+  var GHCConcSignalSignalHandlerStore: Any? = null
+}
+var globalHeap = ByteArray(0)
 
-@CompilerDirectives.TruffleBoundary
-fun getMD5(): MessageDigest = MessageDigest.getInstance("MD5")
 
+@OptIn(kotlin.ExperimentalUnsignedTypes::class)
 val primFCalls: Map<String, () -> StgPrimOp> = mapOf(
   // TODO: do something safer! (use x to store MessageDigest object?)
   "__hsbase_MD5Init" to wrap2Boundary { x: StgAddr, y: VoidInh ->
@@ -104,6 +108,11 @@ val primFCalls: Map<String, () -> StgPrimOp> = mapOf(
       panic("nyi ghczuwrapperZC20ZCbaseZCSystemziPosixziInternalsZCwrite")
     }
   },
+  "ghczuwrapperZC22ZCbaseZCSystemziPosixziInternalsZCread" to wrap4Boundary { x: StgInt, y: StgAddr, z: StgWord, _: VoidInh ->
+    UnboxedTuple(arrayOf(StgInt(posix.read(x.x.toInt(), y.asBuffer(), z.x.toLong()))))
+  },
+
+  "shutdownHaskellAndExit" to wrap3Boundary { x: StgInt, _: StgInt, _: VoidInh -> throw TruffleStgExitException(x.x.toInt()) },
 
   "hs_free_stable_ptr" to wrap2 { x: StablePtr, _: VoidInh ->
     // FIXME: getting deRefStablePtr after freeStablePtr, so i'm disabling this for now
@@ -117,7 +126,7 @@ val primFCalls: Map<String, () -> StgPrimOp> = mapOf(
     // TODO
     UnboxedTuple(arrayOf(StgInt(-1)))
   },
-  "getProgArgv" to wrap3Boundary { argc: StgAddr, argv: StgAddr, v: VoidInh ->
+  "getProgArgv" to wrap3Boundary { argc: StgAddr, argv: StgAddr, _: VoidInh ->
     val args = arrayOf(
       "trufflestg",
       *Language.currentContext().env.applicationArguments
@@ -136,10 +145,10 @@ val primFCalls: Map<String, () -> StgPrimOp> = mapOf(
     argv.arr.write(argv.offset, argvIx.toLong().toByteArray())
     UnboxedTuple(arrayOf())
   },
-  "u_towupper" to wrap2 { x: StgInt, w: VoidInh ->
+  "u_towupper" to wrap2 { x: StgInt, _: VoidInh ->
     UnboxedTuple(arrayOf(StgInt(Character.toUpperCase(x.x.toInt()).toLong())))
   },
-  "u_gencat" to wrap2 { x: StgInt, w: VoidInh ->
+  "u_gencat" to wrap2 { x: StgInt, _: VoidInh ->
     UnboxedTuple(arrayOf(StgInt(when (Character.getType(x.x.toInt()).toByte()) {
       // in java's order, mapping to haskell's order
       Character.UNASSIGNED -> 29
@@ -197,6 +206,19 @@ val primFCalls: Map<String, () -> StgPrimOp> = mapOf(
       Character.LOWERCASE_LETTER -> 1
       else -> 0
     }.toLong())))
+  },
+  "u_iswalnum" to wrap2 { x: StgInt, _: VoidInh ->
+    UnboxedTuple(arrayOf(StgInt(when (Character.getType(x.x.toInt()).toByte()) {
+      Character.UPPERCASE_LETTER -> 1
+      Character.LOWERCASE_LETTER -> 1
+      Character.TITLECASE_LETTER -> 1
+      Character.MODIFIER_LETTER -> 1
+      Character.OTHER_LETTER -> 1
+      Character.OTHER_NUMBER -> 1
+      Character.DECIMAL_DIGIT_NUMBER -> 1
+      Character.LETTER_NUMBER -> 1
+      else -> 0
+    }.toLong())))
   }
 )
 
@@ -213,4 +235,4 @@ inline fun <reified X, reified Y, reified Z, reified W : Any> wrap3Boundary(cros
 }
 inline fun <reified X, reified Y, reified Z, reified W : Any, reified A> wrap4Boundary(crossinline f: (X, Y, Z, A) -> W): () -> StgPrimOp = {
   object : StgPrimOp4() { @CompilerDirectives.TruffleBoundary override fun execute(x: Any, y: Any, z: Any, a: Any): Any = f((x as? X)!!, (y as? Y)!!, (z as? Z)!!, (a as? A)!!) }
-}
\ No newline at end of file
+}
diff --git a/src/trufflestg/jit/StgPrim.kt b/src/trufflestg/jit/StgPrim.kt
index 46a061a..72e99e0 100644
--- a/src/trufflestg/jit/StgPrim.kt
+++ b/src/trufflestg/jit/StgPrim.kt
@@ -3,9 +3,6 @@ package trufflestg.jit
 
 import com.oracle.truffle.api.CompilerDirectives
 import com.oracle.truffle.api.ExactMath
-import trufflestg.data.*
-import trufflestg.panic
-import trufflestg.todo
 import com.oracle.truffle.api.dsl.TypeSystemReference
 import com.oracle.truffle.api.frame.VirtualFrame
 import com.oracle.truffle.api.nodes.ExplodeLoop
@@ -13,8 +10,10 @@ import com.oracle.truffle.api.nodes.Node
 import trufflestg.array_utils.map
 import trufflestg.array_utils.toByteArray
 import trufflestg.array_utils.write
-import com.oracle.truffle.api.dsl.NodeChild
-import trufflestg.data.DataTypes
+import trufflestg.data.*
+import trufflestg.panic
+import trufflestg.todo
+import java.lang.ArithmeticException
 import java.nio.ByteBuffer
 
 
@@ -45,6 +44,15 @@ class StgPrim(
 // i think usually we need to whnf ourselves?
 @OptIn(ExperimentalUnsignedTypes::class)
 val primOps: Map<String, () -> StgPrimOp> = mapOf(
+  "gtChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x > y.x) 1L else 0L) },
+  "geChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x >= y.x) 1L else 0L) },
+  "eqChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x == y.x) 1L else 0L) },
+  "neChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x != y.x) 1L else 0L) },
+  "ltChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x < y.x) 1L else 0L) },
+  "leChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x <= y.x) 1L else 0L) },
+
+  "ord#" to wrap1 { x: StgChar -> StgInt(x.x.toLong()) }, // TODO: should this be an unsigned conversion?
+
   "catch#" to { object : StgPrimOp(3) {
     @field:Child var callWhnf1 = CallWhnf(1, false)
     @field:Child var callWhnf2 = CallWhnf(2, false)
@@ -75,10 +83,17 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
   ">=#" to wrap2 { x: StgInt, y: StgInt -> StgInt(if (x.x >= y.x) 1L else 0L) },
   "==#" to wrap2 { x: StgInt, y: StgInt -> StgInt(if (x.x == y.x) 1L else 0L) },
 
+  "andI#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x and y.x) },
+  "orI#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x or y.x) },
+  "xorI#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x xor y.x) },
+
   "addIntC#" to wrap2 { x: StgInt, y: StgInt ->
-    // TODO: slow
-    try { UnboxedTuple(arrayOf(StgInt(Math.addExact(x.x, y.x)), StgInt(0L))) }
-    catch (e: ArithmeticException) { UnboxedTuple(arrayOf(StgInt(x.x + y.x), StgInt(1L))) }
+    val r = x.x + y.x
+    UnboxedTuple(arrayOf(StgInt(r), StgInt(if(x.x xor r and (y.x xor r) < 0) 1L else 0L)))
+  },
+  "subIntC#" to wrap2 { x: StgInt, y: StgInt ->
+    val r = x.x - y.x
+    UnboxedTuple(arrayOf(StgInt(r), StgInt(if(x.x xor r and (y.x xor r) < 0) 1L else 0L)))
   },
 
   "timesInt2#" to wrap2 { x: StgInt, y: StgInt ->
@@ -134,11 +149,7 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
   "readMutVar#" to wrap2 { x: StgMutVar, _: VoidInh -> UnboxedTuple(arrayOf(x.x)) },
   "writeMutVar#" to wrap3 { x: StgMutVar, y: Any, v: VoidInh -> x.x = y; v },
 
-  "leChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x <= y.x) 1L else 0L) },
-  "gtChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x > y.x) 1L else 0L) },
-  "geChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x >= y.x) 1L else 0L) },
-  "ord#" to wrap1 { x: StgChar -> StgInt(x.x.toLong()) }, // TODO: should this be an unsigned conversion?
-  "chr#" to wrap1 { x: StgInt -> StgChar(x.x.toInt()) }, // TODO: ^
+  "chr#" to wrap1 { x: StgInt -> StgChar(x.x.toInt()) }, // TODO: should this be an unsigned conversion?
 
   "int2Word#" to wrap1 { x: StgInt -> StgWord(x.x.toULong()) },
   "word2Int#" to wrap1 { x: StgWord -> StgInt(x.x.toLong()) },
@@ -149,7 +160,6 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
   "eqWord#" to wrap2 { x: StgWord, y: StgWord -> StgInt(if (x.x == y.x) 1L else 0L) },
   "minusWord#" to wrap2 { x: StgWord, y: StgWord -> StgWord(x.x - y.x) },
 
-  "eqChar#" to wrap2 { x: StgChar, y: StgChar -> StgInt(if (x.x == y.x) 1L else 0L) },
 
   "tagToEnum#" to { object : StgPrimOp1() {
     // TODO: need to do this lazily because parent isn't set at initialization
@@ -222,12 +232,22 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
   "writeWideCharOffAddr#" to wrap4 { x: StgAddr, y: StgInt, z: StgChar, v: VoidInh ->
     x.arr.write(x.offset + 4*y.x.toInt(), z.x.toByteArray()); v },
 
+  "writeWordArray#" to wrap4 { x: StgMutableByteArray, y: StgInt, z: StgWord, v: VoidInh ->
+    x.arr.write(8*y.toInt(), z.x.toLong()); v },
+
+  "indexWordArray#" to wrap2 { x: StgMutableByteArray, y: StgInt ->
+    StgWord(x.asBuffer().getLong(y.toInt()*8).toULong())
+  },
+
   "plusAddr#" to wrap2 { x: StgAddr, y: StgInt -> StgAddr(x.arr, x.offset + y.x.toInt()) },
 
   // TODO: make sure these are right
   "uncheckedIShiftL#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x shl y.x.toInt()) },
-  "uncheckedShiftRL#" to wrap2 { x: StgWord, y: StgInt -> StgWord(x.x shr y.x.toInt()) },
+  "uncheckedIShiftRL#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x ushr y.x.toInt()) },
+  "uncheckedIShiftRA#" to wrap2 { x: StgInt, y: StgInt -> StgInt(x.x shr y.x.toInt()) },
   "uncheckedShiftL#" to wrap2 { x: StgWord, y: StgInt -> StgWord(x.x shl y.x.toInt()) },
+  "uncheckedShiftRL#" to wrap2 { x: StgWord, y: StgInt -> StgWord(x.x shr y.x.toInt()) },
+
   "or#" to wrap2 { x: StgWord, y: StgWord -> StgWord(x.x or y.x) },
 
   // TODO?
@@ -239,9 +259,12 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
     override fun run(frame: VirtualFrame, args: Array<Any>): Any = callWhnf.execute(frame, args[0], arrayOf())
   }},
 
-  "raise#" to wrap1 { e: Any -> (throw HaskellException(e)) as VoidInh },
-  "raiseIO#" to wrap2 { e: Any, _: VoidInh -> (throw HaskellException(e)) as VoidInh },
+  "raise#" to wrap1 { e: Any -> throw HaskellException(e) },
+  "raiseIO#" to wrap2 { e: Any, _: VoidInh -> throw HaskellException(e) },
 
+  "newByteArray#" to wrap2 { x: StgInt, _: VoidInh ->
+    UnboxedTuple(arrayOf(StgMutableByteArray(ByteArray(x.toInt()))))
+  },
   // TODO: actually pin & align? only matters if we want to use native code
   // FIXME: or for readAddrOffAddr, or if casted to Addr?
   "newAlignedPinnedByteArray#" to wrap3 { x: StgInt, alignment: StgInt, _: VoidInh ->
@@ -251,7 +274,9 @@ val primOps: Map<String, () -> StgPrimOp> = mapOf(
   "unsafeFreezeByteArray#" to wrap2 { arr: StgMutableByteArray, _: VoidInh ->
     arr.frozen = true
     UnboxedTuple(arrayOf(arr)) },
-  "byteArrayContents#" to wrap1 { arr: StgMutableByteArray -> StgAddr(arr.arr, 0) }
+  "byteArrayContents#" to wrap1 { arr: StgMutableByteArray -> StgAddr(arr.arr, 0) },
+
+  "sizeofByteArray#" to wrap1 { x: StgMutableByteArray -> StgInt(x.arr.size.toLong()) }
 )
 
 
diff --git a/src/trufflestg/stg/elab.kt b/src/trufflestg/stg/elab.kt
index 2a0ae2d..f24dbfb 100644
--- a/src/trufflestg/stg/elab.kt
+++ b/src/trufflestg/stg/elab.kt
@@ -362,6 +362,7 @@ class Module(
     }
   }.associateBy { it.binder.binderId }
 
+  // TODO: build classes lazily
   val tyCons: Map<Stg.TyConId, TyCon>
   val dataCons: Map<Stg.DataConId, DataConInfo>
   init {