diff --git a/nac3core/src/codegen/expr.rs b/nac3core/src/codegen/expr.rs
index 494b2380..4118716e 100644
--- a/nac3core/src/codegen/expr.rs
+++ b/nac3core/src/codegen/expr.rs
@@ -43,6 +43,12 @@ use nac3parser::ast::{
     Unaryop,
 };
 
+use super::structure::cslice::CSlice;
+use super::{
+    model::*,
+    structure::exception::{Exception, ExceptionId},
+};
+
 pub fn get_subst_key(
     unifier: &mut Unifier,
     obj: Option<Type>,
@@ -281,24 +287,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                     None
                 }
             }
-            Constant::Str(v) => {
-                assert!(self.unifier.unioned(ty, self.primitives.str));
-                if let Some(v) = self.const_strings.get(v) {
-                    Some(*v)
-                } else {
-                    let str_ptr = self
-                        .builder
-                        .build_global_string_ptr(v, "const")
-                        .map(|v| v.as_pointer_value().into())
-                        .unwrap();
-                    let size = generator.get_size_type(self.ctx).const_int(v.len() as u64, false);
-                    let ty = self.get_llvm_type(generator, self.primitives.str);
-                    let val =
-                        ty.into_struct_type().const_named_struct(&[str_ptr, size.into()]).into();
-                    self.const_strings.insert(v.to_string(), val);
-                    Some(val)
-                }
-            }
+            Constant::Str(s) => Some(self.gen_string(generator, s).value.into()),
             Constant::Ellipsis => {
                 let msg = self.gen_string(generator, "NotImplementedError");
 
@@ -560,96 +549,114 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
     }
 
     /// Helper function for generating a LLVM variable storing a [String].
-    pub fn gen_string<G, S>(&mut self, generator: &mut G, s: S) -> BasicValueEnum<'ctx>
+    pub fn gen_string<G>(&mut self, generator: &mut G, string: &str) -> Struct<'ctx, CSlice>
     where
         G: CodeGenerator + ?Sized,
-        S: Into<String>,
     {
-        self.gen_const(generator, &Constant::Str(s.into()), self.primitives.str).unwrap()
+        self.const_strings.get(string).copied().unwrap_or_else(|| {
+            let type_context = generator.type_context(self.ctx);
+            let sizet_model = IntModel(SizeT);
+            let pbyte_model = PtrModel(IntModel(Byte));
+            let cslice_model = StructModel(CSlice);
+
+            let base = self.builder.build_global_string_ptr(string, "constant_string").unwrap();
+            let base = pbyte_model.believe_value(base.as_pointer_value());
+
+            let len = sizet_model.constant(type_context, self.ctx, string.len() as u64);
+
+            let cslice = cslice_model.create_const(type_context, self, base, len);
+
+            self.const_strings.insert(string.to_owned(), cslice);
+
+            cslice
+        })
     }
 
     pub fn raise_exn<G: CodeGenerator + ?Sized>(
         &mut self,
         generator: &mut G,
         name: &str,
-        msg: BasicValueEnum<'ctx>,
-        params: [Option<IntValue<'ctx>>; 3],
+        msg: Struct<'ctx, CSlice>,
+        params: [Option<Int<'ctx, Int64>>; 3],
         loc: Location,
     ) {
-        let zelf = if let Some(exception_val) = self.exception_val {
-            exception_val
-        } else {
-            let ty = self.get_llvm_type(generator, self.primitives.exception).into_pointer_type();
-            let zelf_ty: BasicTypeEnum = ty.get_element_type().into_struct_type().into();
-            let zelf = generator.gen_var_alloc(self, zelf_ty, Some("exn")).unwrap();
-            *self.exception_val.insert(zelf)
-        };
-        let int32 = self.ctx.i32_type();
-        let zero = int32.const_zero();
-        unsafe {
-            let id_ptr = self.builder.build_in_bounds_gep(zelf, &[zero, zero], "exn.id").unwrap();
-            let id = self.resolver.get_string_id(name);
-            self.builder.build_store(id_ptr, int32.const_int(id as u64, false)).unwrap();
-            let ptr = self
-                .builder
-                .build_in_bounds_gep(zelf, &[zero, int32.const_int(5, false)], "exn.msg")
-                .unwrap();
-            self.builder.build_store(ptr, msg).unwrap();
-            let i64_zero = self.ctx.i64_type().const_zero();
-            for (i, attr_ind) in [6, 7, 8].iter().enumerate() {
-                let ptr = self
-                    .builder
-                    .build_in_bounds_gep(
-                        zelf,
-                        &[zero, int32.const_int(*attr_ind, false)],
-                        "exn.param",
-                    )
-                    .unwrap();
-                let val = params[i].map_or(i64_zero, |v| {
-                    self.builder.build_int_s_extend(v, self.ctx.i64_type(), "sext").unwrap()
-                });
-                self.builder.build_store(ptr, val).unwrap();
+        let type_context = generator.type_context(self.ctx);
+        let exn_model = StructModel(Exception);
+        let exn_id_model = IntModel(ExceptionId::default());
+
+        let exn_id =
+            exn_id_model.constant(type_context, self.ctx, self.resolver.get_string_id(name) as u64);
+        let exn = self.exception_val.unwrap_or_else(|| {
+            let exn = exn_model.var_alloca(generator, self, Some("exn")).unwrap();
+            *self.exception_val.insert(exn)
+        });
+
+        exn.gep(self, |f| f.id).store(self, exn_id);
+        exn.gep(self, |f| f.msg).store(self, msg);
+        for (i, param) in params.iter().enumerate() {
+            if let Some(param) = param {
+                exn.gep(self, |f| f.params[i]).store(self, *param);
             }
         }
-        gen_raise(generator, self, Some(&zelf.into()), loc);
+
+        gen_raise(generator, self, Some(exn), loc);
     }
 
     pub fn make_assert<G: CodeGenerator + ?Sized>(
         &mut self,
         generator: &mut G,
-        cond: IntValue<'ctx>,
+        cond: IntValue<'ctx>, // IntType can have arbitrary bit width
         err_name: &str,
         err_msg: &str,
         params: [Option<IntValue<'ctx>>; 3],
         loc: Location,
     ) {
+        let type_context = generator.type_context(self.ctx);
+        let param_model = IntModel(Int64);
+
         let err_msg = self.gen_string(generator, err_msg);
+
+        let ctx = self.ctx;
+        let params =
+            params.map(|p| p.map(|p| param_model.check_value(type_context, ctx, p).unwrap()));
+
         self.make_assert_impl(generator, cond, err_name, err_msg, params, loc);
     }
 
     pub fn make_assert_impl<G: CodeGenerator + ?Sized>(
         &mut self,
         generator: &mut G,
-        cond: IntValue<'ctx>,
+        cond: IntValue<'ctx>, // IntType can have arbitrary bit width
         err_name: &str,
-        err_msg: BasicValueEnum<'ctx>,
-        params: [Option<IntValue<'ctx>>; 3],
+        err_msg: Struct<'ctx, CSlice>,
+        params: [Option<Int<'ctx, Int64>>; 3],
         loc: Location,
     ) {
-        let i1 = self.ctx.bool_type();
-        let i1_true = i1.const_all_ones();
-        // we assume that the condition is most probably true, so the normal path is the most
-        // probable path
-        // even if this assumption is violated, it does not matter as exception unwinding is
-        // slow anyway...
-        let cond = call_expect(self, cond, i1_true, Some("expect"));
+        let type_context = generator.type_context(self.ctx);
+        let bool_model = IntModel(Bool);
+
+        // We assume that the condition is most probably true, so the normal path is the most
+        // probable path even if this assumption is violated, it does not matter as exception unwinding is.
+        let cond = call_expect(
+            self,
+            generator.bool_to_i1(self, cond),
+            bool_model.const_true(type_context, self.ctx).value,
+            Some("expect"),
+        );
+
         let current_bb = self.builder.get_insert_block().unwrap();
         let current_fun = current_bb.get_parent().unwrap();
+
         let then_block = self.ctx.insert_basic_block_after(current_bb, "succ");
         let exn_block = self.ctx.append_basic_block(current_fun, "fail");
+
         self.builder.build_conditional_branch(cond, then_block, exn_block).unwrap();
+
+        // Inserting into `exn_block`
         self.builder.position_at_end(exn_block);
         self.raise_exn(generator, err_name, err_msg, params, loc);
+
+        // Continuation
         self.builder.position_at_end(then_block);
     }
 }
diff --git a/nac3core/src/codegen/irrt/mod.rs b/nac3core/src/codegen/irrt/mod.rs
index 002cdb37..2a4c8b83 100644
--- a/nac3core/src/codegen/irrt/mod.rs
+++ b/nac3core/src/codegen/irrt/mod.rs
@@ -2,6 +2,7 @@ use crate::typecheck::typedef::Type;
 
 mod test;
 
+use super::model::*;
 use super::{
     classes::{
         ArrayLikeIndexer, ArrayLikeValue, ArraySliceValue, ListValue, NDArrayValue,
@@ -416,14 +417,29 @@ pub fn list_slice_assignment<'ctx, G: CodeGenerator + ?Sized>(
         .unwrap();
     let cond_1 = ctx.builder.build_and(dest_step_eq_one, src_slt_dest, "slice_cond_1").unwrap();
     let cond = ctx.builder.build_or(src_eq_dest, cond_1, "slice_cond").unwrap();
-    ctx.make_assert(
-        generator,
-        cond,
-        "0:ValueError",
-        "attempt to assign sequence of size {0} to slice of size {1} with step size {2}",
-        [Some(src_slice_len), Some(dest_slice_len), Some(dest_idx.2)],
-        ctx.current_loc,
-    );
+
+    // TODO: Temporary fix. Rewrite `list_slice_assignment` later
+    // Exception params should have been i64
+    {
+        let type_context = generator.type_context(ctx.ctx);
+        let param_model = IntModel(Int64);
+
+        let src_slice_len =
+            param_model.s_extend_or_bit_cast(type_context, ctx, src_slice_len, "src_slice_len");
+        let dest_slice_len =
+            param_model.s_extend_or_bit_cast(type_context, ctx, dest_slice_len, "dest_slice_len");
+        let dest_idx_2 =
+            param_model.s_extend_or_bit_cast(type_context, ctx, dest_idx.2, "dest_idx_2");
+
+        ctx.make_assert(
+            generator,
+            cond,
+            "0:ValueError",
+            "attempt to assign sequence of size {0} to slice of size {1} with step size {2}",
+            [Some(src_slice_len.value), Some(dest_slice_len.value), Some(dest_idx_2.value)],
+            ctx.current_loc,
+        );
+    }
 
     let new_len = {
         let args = vec![
diff --git a/nac3core/src/codegen/mod.rs b/nac3core/src/codegen/mod.rs
index dc53953c..244b8f8d 100644
--- a/nac3core/src/codegen/mod.rs
+++ b/nac3core/src/codegen/mod.rs
@@ -24,6 +24,7 @@ use inkwell::{
     AddressSpace, IntPredicate, OptimizationLevel,
 };
 use itertools::Itertools;
+use model::*;
 use nac3parser::ast::{Location, Stmt, StrRef};
 use parking_lot::{Condvar, Mutex};
 use std::collections::{HashMap, HashSet};
@@ -32,6 +33,7 @@ use std::sync::{
     Arc,
 };
 use std::thread;
+use structure::{cslice::CSlice, exception::Exception};
 
 pub mod builtin_fns;
 pub mod classes;
@@ -44,6 +46,7 @@ pub mod llvm_intrinsics;
 pub mod model;
 pub mod numpy;
 pub mod stmt;
+pub mod structure;
 
 #[cfg(test)]
 mod test;
@@ -169,11 +172,11 @@ pub struct CodeGenContext<'ctx, 'a> {
     pub registry: &'a WorkerRegistry,
 
     /// Cache for constant strings.
-    pub const_strings: HashMap<String, BasicValueEnum<'ctx>>,
+    pub const_strings: HashMap<String, Struct<'ctx, CSlice>>,
 
     /// [`BasicBlock`] containing all `alloca` statements for the current function.
     pub init_bb: BasicBlock<'ctx>,
-    pub exception_val: Option<PointerValue<'ctx>>,
+    pub exception_val: Option<Ptr<'ctx, StructModel<Exception>>>,
 
     /// The header and exit basic blocks of a loop in this context. See
     /// <https://llvm.org/docs/LoopTerminology.html> for explanation of these terminology.
@@ -665,43 +668,20 @@ pub fn gen_func_impl<
         ..primitives
     };
 
-    let mut type_cache: HashMap<_, _> = [
+    let type_context = generator.type_context(context);
+    let cslice_model = StructModel(CSlice);
+    let pexn_model = PtrModel(StructModel(Exception));
+
+    let mut type_cache: HashMap<_, BasicTypeEnum<'ctx>> = [
         (primitives.int32, context.i32_type().into()),
         (primitives.int64, context.i64_type().into()),
         (primitives.uint32, context.i32_type().into()),
         (primitives.uint64, context.i64_type().into()),
         (primitives.float, context.f64_type().into()),
         (primitives.bool, context.i8_type().into()),
-        (primitives.str, {
-            let name = "str";
-            match module.get_struct_type(name) {
-                None => {
-                    let str_type = context.opaque_struct_type("str");
-                    let fields = [
-                        context.i8_type().ptr_type(AddressSpace::default()).into(),
-                        generator.get_size_type(context).into(),
-                    ];
-                    str_type.set_body(&fields, false);
-                    str_type.into()
-                }
-                Some(t) => t.as_basic_type_enum(),
-            }
-        }),
+        (primitives.str, cslice_model.get_type(type_context, context).into()),
         (primitives.range, RangeType::new(context).as_base_type().into()),
-        (primitives.exception, {
-            let name = "Exception";
-            if let Some(t) = module.get_struct_type(name) {
-                t.ptr_type(AddressSpace::default()).as_basic_type_enum()
-            } else {
-                let exception = context.opaque_struct_type("Exception");
-                let int32 = context.i32_type().into();
-                let int64 = context.i64_type().into();
-                let str_ty = module.get_struct_type("str").unwrap().as_basic_type_enum();
-                let fields = [int32, str_ty, int32, int32, str_ty, str_ty, int64, int64, int64];
-                exception.set_body(&fields, false);
-                exception.ptr_type(AddressSpace::default()).as_basic_type_enum()
-            }
-        }),
+        (primitives.exception, pexn_model.get_type(type_context, context).into()),
     ]
     .iter()
     .copied()
diff --git a/nac3core/src/codegen/numpy.rs b/nac3core/src/codegen/numpy.rs
index 92e07059..0732f2fb 100644
--- a/nac3core/src/codegen/numpy.rs
+++ b/nac3core/src/codegen/numpy.rs
@@ -254,7 +254,7 @@ fn ndarray_zero_value<'ctx, G: CodeGenerator + ?Sized>(
     } else if ctx.unifier.unioned(elem_ty, ctx.primitives.bool) {
         ctx.ctx.bool_type().const_zero().into()
     } else if ctx.unifier.unioned(elem_ty, ctx.primitives.str) {
-        ctx.gen_string(generator, "")
+        ctx.gen_string(generator, "").value.into()
     } else {
         unreachable!()
     }
@@ -282,7 +282,7 @@ fn ndarray_one_value<'ctx, G: CodeGenerator + ?Sized>(
     } else if ctx.unifier.unioned(elem_ty, ctx.primitives.bool) {
         ctx.ctx.bool_type().const_int(1, false).into()
     } else if ctx.unifier.unioned(elem_ty, ctx.primitives.str) {
-        ctx.gen_string(generator, "1")
+        ctx.gen_string(generator, "1").value.into()
     } else {
         unreachable!()
     }
diff --git a/nac3core/src/codegen/stmt.rs b/nac3core/src/codegen/stmt.rs
index ee581959..88f80c97 100644
--- a/nac3core/src/codegen/stmt.rs
+++ b/nac3core/src/codegen/stmt.rs
@@ -1,8 +1,11 @@
+use super::model::*;
+use super::structure::cslice::CSlice;
 use super::{
     super::symbol_resolver::ValueEnum,
     expr::destructure_range,
     irrt::{handle_slice_indices, list_slice_assignment},
-    CodeGenContext, CodeGenerator,
+    structure::exception::Exception,
+    CodeGenContext, CodeGenerator, Int32, IntModel, Ptr, StructModel,
 };
 use crate::{
     codegen::{
@@ -1126,47 +1129,37 @@ pub fn exn_constructor<'ctx>(
 pub fn gen_raise<'ctx, G: CodeGenerator + ?Sized>(
     generator: &mut G,
     ctx: &mut CodeGenContext<'ctx, '_>,
-    exception: Option<&BasicValueEnum<'ctx>>,
+    exception: Option<Ptr<'ctx, StructModel<Exception>>>,
     loc: Location,
 ) {
-    if let Some(exception) = exception {
-        unsafe {
-            let int32 = ctx.ctx.i32_type();
-            let zero = int32.const_zero();
-            let exception = exception.into_pointer_value();
-            let file_ptr = ctx
-                .builder
-                .build_in_bounds_gep(exception, &[zero, int32.const_int(1, false)], "file_ptr")
-                .unwrap();
-            let filename = ctx.gen_string(generator, loc.file.0);
-            ctx.builder.build_store(file_ptr, filename).unwrap();
-            let row_ptr = ctx
-                .builder
-                .build_in_bounds_gep(exception, &[zero, int32.const_int(2, false)], "row_ptr")
-                .unwrap();
-            ctx.builder.build_store(row_ptr, int32.const_int(loc.row as u64, false)).unwrap();
-            let col_ptr = ctx
-                .builder
-                .build_in_bounds_gep(exception, &[zero, int32.const_int(3, false)], "col_ptr")
-                .unwrap();
-            ctx.builder.build_store(col_ptr, int32.const_int(loc.column as u64, false)).unwrap();
+    if let Some(pexn) = exception {
+        let type_context = generator.type_context(ctx.ctx);
+        let i32_model = IntModel(Int32);
+        let cslice_model = StructModel(CSlice);
 
-            let current_fun = ctx.builder.get_insert_block().unwrap().get_parent().unwrap();
-            let fun_name = ctx.gen_string(generator, current_fun.get_name().to_str().unwrap());
-            let name_ptr = ctx
-                .builder
-                .build_in_bounds_gep(exception, &[zero, int32.const_int(4, false)], "name_ptr")
-                .unwrap();
-            ctx.builder.build_store(name_ptr, fun_name).unwrap();
-        }
+        // Get and store filename
+        let filename = loc.file.0;
+        let filename = ctx.gen_string(generator, &String::from(filename)).value;
+        let filename = cslice_model.check_value(type_context, ctx.ctx, filename).unwrap();
+        pexn.gep(ctx, |f| f.filename).store(ctx, filename);
+
+        let row = i32_model.constant(type_context, ctx.ctx, loc.row as u64);
+        pexn.gep(ctx, |f| f.line).store(ctx, row);
+
+        let column = i32_model.constant(type_context, ctx.ctx, loc.column as u64);
+        pexn.gep(ctx, |f| f.column).store(ctx, column);
+
+        let current_fn = ctx.builder.get_insert_block().unwrap().get_parent().unwrap();
+        let fn_name = ctx.gen_string(generator, current_fn.get_name().to_str().unwrap());
+        pexn.gep(ctx, |f| f.function).store(ctx, fn_name);
 
         let raise = get_builtins(generator, ctx, "__nac3_raise");
-        let exception = *exception;
-        ctx.build_call_or_invoke(raise, &[exception], "raise");
+        ctx.build_call_or_invoke(raise, &[pexn.value.into()], "raise");
     } else {
         let resume = get_builtins(generator, ctx, "__nac3_resume");
         ctx.build_call_or_invoke(resume, &[], "resume");
     }
+
     ctx.builder.build_unreachable().unwrap();
 }
 
@@ -1627,30 +1620,43 @@ pub fn gen_stmt<G: CodeGenerator>(
                 } else {
                     return Ok(());
                 };
-                gen_raise(generator, ctx, Some(&exc), stmt.location);
+
+                let type_context = generator.type_context(ctx.ctx);
+                let pexn_model = PtrModel(StructModel(Exception));
+                let exn = pexn_model.check_value(type_context, ctx.ctx, exc).unwrap();
+
+                gen_raise(generator, ctx, Some(exn), stmt.location);
             } else {
                 gen_raise(generator, ctx, None, stmt.location);
             }
         }
         StmtKind::Assert { test, msg, .. } => {
-            let test = if let Some(v) = generator.gen_expr(ctx, test)? {
-                v.to_basic_value_enum(ctx, generator, test.custom.unwrap())?
-            } else {
+            let type_context = generator.type_context(ctx.ctx);
+            let byte_model = IntModel(Byte);
+            let cslice_model = StructModel(CSlice);
+
+            let Some(test) = generator.gen_expr(ctx, test)? else {
                 return Ok(());
             };
+            let test = test.to_basic_value_enum(ctx, generator, ctx.primitives.bool)?;
+            let test = byte_model.check_value(type_context, ctx.ctx, test).unwrap(); // Python `bool` is represented as `i8` in nac3core
+
+            // Check `msg`
             let err_msg = match msg {
                 Some(msg) => {
-                    if let Some(v) = generator.gen_expr(ctx, msg)? {
-                        v.to_basic_value_enum(ctx, generator, msg.custom.unwrap())?
-                    } else {
+                    let Some(msg) = generator.gen_expr(ctx, msg)? else {
                         return Ok(());
-                    }
+                    };
+
+                    let msg = msg.to_basic_value_enum(ctx, generator, ctx.primitives.str)?;
+                    cslice_model.check_value(type_context, ctx.ctx, msg).unwrap()
                 }
                 None => ctx.gen_string(generator, ""),
             };
+
             ctx.make_assert_impl(
                 generator,
-                generator.bool_to_i1(ctx, test.into_int_value()),
+                test.value,
                 "0:AssertionError",
                 err_msg,
                 [None, None, None],
diff --git a/nac3core/src/codegen/structure/cslice.rs b/nac3core/src/codegen/structure/cslice.rs
new file mode 100644
index 00000000..9d4b2a4c
--- /dev/null
+++ b/nac3core/src/codegen/structure/cslice.rs
@@ -0,0 +1,43 @@
+use crate::codegen::{model::*, CodeGenContext};
+
+/// Fields of [`CSlice<'ctx>`].
+pub struct CSliceFields<F: FieldVisitor> {
+    /// Pointer to the data.
+    pub base: F::Field<PtrModel<IntModel<Byte>>>,
+    /// Number of bytes of the data.
+    pub len: F::Field<IntModel<SizeT>>,
+}
+
+/// See <https://crates.io/crates/cslice>.
+///
+/// Additionally, see <https://github.com/m-labs/artiq/blob/b0d2705c385f64b6e6711c1726cd9178f40b598e/artiq/firmware/libeh/eh_artiq.rs>)
+/// for ARTIQ-specific notes.
+#[derive(Debug, Clone, Copy, Default)]
+pub struct CSlice;
+
+impl StructKind for CSlice {
+    type Fields<F: FieldVisitor> = CSliceFields<F>;
+
+    fn visit_fields<F: FieldVisitor>(&self, visitor: &mut F) -> Self::Fields<F> {
+        Self::Fields { base: visitor.add("base"), len: visitor.add("len") }
+    }
+}
+
+impl StructModel<CSlice> {
+    /// Create a [`CSlice`].
+    ///
+    /// `base` and `len` must be LLVM global constants.
+    pub fn create_const<'ctx>(
+        &self,
+        type_context: TypeContext<'ctx>,
+        ctx: &CodeGenContext<'ctx, '_>,
+        base: Ptr<'ctx, IntModel<Byte>>,
+        len: Int<'ctx, SizeT>,
+    ) -> Struct<'ctx, CSlice> {
+        let value = self
+            .0
+            .get_struct_type(type_context, ctx.ctx)
+            .const_named_struct(&[base.value.into(), len.value.into()]);
+        self.believe_value(value)
+    }
+}
diff --git a/nac3core/src/codegen/structure/exception.rs b/nac3core/src/codegen/structure/exception.rs
new file mode 100644
index 00000000..5ddb8ce1
--- /dev/null
+++ b/nac3core/src/codegen/structure/exception.rs
@@ -0,0 +1,57 @@
+use crate::codegen::model::*;
+
+use super::cslice::CSlice;
+
+/// The LLVM int type of an Exception ID.
+pub type ExceptionId = Int32;
+
+/// Fields of [`Exception<'ctx>`]
+///
+/// The definition came from `pub struct Exception<'a>` in
+/// <https://github.com/m-labs/artiq/blob/master/artiq/firmware/libeh/eh_artiq.rs>.
+pub struct ExceptionFields<F: FieldVisitor> {
+    /// nac3core's ID of the exception
+    pub id: F::Field<IntModel<ExceptionId>>,
+    /// The name of the file this `Exception` was raised in.
+    pub filename: F::Field<StructModel<CSlice>>,
+    /// The line number in the file this `Exception` was raised in.
+    pub line: F::Field<IntModel<Int32>>,
+    /// The column number in the file this `Exception` was raised in.
+    pub column: F::Field<IntModel<Int32>>,
+    /// The name of the Python function this `Exception` was raised in.
+    pub function: F::Field<StructModel<CSlice>>,
+    /// The message of this Exception.
+    ///
+    /// The message can optionally contain integer parameters `{0}`, `{1}`, and `{2}` in its string,
+    /// where they will be substituted by `params[0]`, `params[1]`, and `params[2]` respectively (as `int64_t`s).
+    /// Here is an example:
+    ///
+    /// ```ignore
+    /// "Index {0} is out of bounds! List only has {1} element(s)."
+    /// ```
+    ///
+    /// In this case, `params[0]` and `params[1]` must be specified, and `params[2]` is ***unused***.
+    /// Having only 3 parameters is a constraint in ARTIQ.
+    pub msg: F::Field<StructModel<CSlice>>,
+    pub params: [F::Field<IntModel<Int64>>; 3],
+}
+
+/// nac3core & ARTIQ's Exception
+#[derive(Debug, Clone, Copy, Default)]
+pub struct Exception;
+
+impl StructKind for Exception {
+    type Fields<F: FieldVisitor> = ExceptionFields<F>;
+
+    fn visit_fields<F: FieldVisitor>(&self, visitor: &mut F) -> Self::Fields<F> {
+        Self::Fields {
+            id: visitor.add("id"),
+            filename: visitor.add("filename"),
+            line: visitor.add("line"),
+            column: visitor.add("column"),
+            function: visitor.add("function"),
+            msg: visitor.add("msg"),
+            params: [visitor.add("params[0]"), visitor.add("params[1]"), visitor.add("params[2]")],
+        }
+    }
+}
diff --git a/nac3core/src/codegen/structure/mod.rs b/nac3core/src/codegen/structure/mod.rs
new file mode 100644
index 00000000..14b596fb
--- /dev/null
+++ b/nac3core/src/codegen/structure/mod.rs
@@ -0,0 +1,2 @@
+pub mod cslice;
+pub mod exception;