diff --git a/nac3core/src/codegen/expr.rs b/nac3core/src/codegen/expr.rs
index 38ac9a63..02bac942 100644
--- a/nac3core/src/codegen/expr.rs
+++ b/nac3core/src/codegen/expr.rs
@@ -43,6 +43,14 @@ use nac3parser::ast::{
     Unaryop,
 };
 
+use super::{
+    model::*,
+    structs::{
+        cslice::CSlice,
+        exception::{Exception, ExceptionId},
+    },
+};
+
 pub fn get_subst_key(
     unifier: &mut Unifier,
     obj: Option<Type>,
@@ -281,24 +289,7 @@ 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 +551,129 @@ 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<'ctx>>
     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 sizet = generator.get_sizet(self.ctx);
+            let pbyte_model = PointerModel(NIntModel(Byte));
+            let cslice_model = StructModel(CSlice { sizet });
+
+            // Create `base`, it has to be a global cstr
+            let base = self.builder.build_global_string_ptr(string, "constant_string").unwrap();
+            let base = pbyte_model.review_value(self.ctx, base.as_pointer_value()).unwrap();
+
+            // Create `len`, it also has to be global
+            let len = sizet.constant(self.ctx, string.len() as u64);
+
+            // Finally, create the global `CSlice` constant of the string.
+            let cslice = cslice_model.create_const(self, base, len);
+
+            // Cache it
+            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<'ctx>>,
+        params: [Option<NInt<'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();
+        // Define all used models
+        let sizet = generator.get_sizet(self.ctx);
+        let exception_id_model = NIntModel(ExceptionId::default());
+        let exception_model = StructModel(Exception { sizet });
+
+        // Get `exn`
+        let exn = self.exception_val.unwrap_or_else(|| {
+            let exn = exception_model.var_alloc(generator, self, Some("exn")).unwrap();
+            *self.exception_val.insert(exn)
+        });
+
+        // Now load everything into `exn`
+        // Store `exception_id`
+        exn.gep(self, |f| f.exception_id).store(
+            self,
+            exception_id_model.constant(self.ctx, self.resolver.get_string_id(name) as u64),
+        );
+
+        // Store `message`
+        exn.gep(self, |f| f.message).store(self, msg);
+
+        // Store `params`
+        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,
     ) {
+        // Define all used models
+        let i64_model = NIntModel(Int64);
+
+        // Create a global `CSlice` constant from `err_msg`
         let err_msg = self.gen_string(generator, err_msg);
+
+        // Check `params`
+        let ctx = self.ctx;
+        let params =
+            params.map(|param| param.map(|param| i64_model.review_value(ctx, param).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<'ctx>>,
+        params: [Option<NInt<'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"));
+        // Define all used models
+        let bool_model = NIntModel(Bool);
+
+        // Truncate `cond` to a `i1`.
+        // So this could accept both nac3core's bool IntType (i8), and i1.
+        let cond = Int::from(cond);
+        let cond = cond.truncate(self, bool_model, "cond_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, cond.value, bool_model.const_true(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/mod.rs b/nac3core/src/codegen/mod.rs
index 715ef6d4..7ce06b35 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 structs::{cslice::CSlice, exception::Exception};
 
 pub mod builtin_fns;
 pub mod classes;
@@ -160,11 +162,11 @@ 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<'ctx>>>,
 
     /// [`BasicBlock`] containing all `alloca` statements for the current function.
     pub init_bb: BasicBlock<'ctx>,
-    pub exception_val: Option<PointerValue<'ctx>>,
+    pub exception_val: Option<Pointer<'ctx, StructModel<Exception<'ctx>>>>,
 
     /// The header and exit basic blocks of a loop in this context. See
     /// <https://llvm.org/docs/LoopTerminology.html> for explanation of these terminology.
@@ -648,47 +650,24 @@ pub fn gen_func_impl<
         ..primitives
     };
 
-    let mut type_cache: HashMap<_, _> = [
+    let sizet = generator.get_sizet(context);
+    let cslice_type = StructModel(CSlice { sizet });
+    let pexception_type = PointerModel(StructModel(Exception { sizet }));
+
+    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_type.get_type(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, pexception_type.get_type(context).into()),
     ]
-    .iter()
-    .copied()
+    .into_iter()
     .collect();
+
     // NOTE: special handling of option cannot use this type cache since it contains type var,
     // handled inside get_llvm_type instead
 
diff --git a/nac3core/src/codegen/model/int.rs b/nac3core/src/codegen/model/int.rs
index c432e89d..f960699f 100644
--- a/nac3core/src/codegen/model/int.rs
+++ b/nac3core/src/codegen/model/int.rs
@@ -55,6 +55,13 @@ impl<'ctx> IntModel<'ctx> {
     }
 }
 
+impl<'ctx> From<IntValue<'ctx>> for Int<'ctx> {
+    fn from(value: IntValue<'ctx>) -> Self {
+        let model = IntModel(value.get_type());
+        model.believe_value(value)
+    }
+}
+
 /// A model representing an [`IntType<'ctx>`] that happens to be defined as `size_t`.
 ///
 /// This is specifically created to guide developers to write `size_t`-dependent code.
diff --git a/nac3core/src/codegen/numpy.rs b/nac3core/src/codegen/numpy.rs
index 7421c894..506b54d9 100644
--- a/nac3core/src/codegen/numpy.rs
+++ b/nac3core/src/codegen/numpy.rs
@@ -252,7 +252,7 @@ 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!()
     }
@@ -280,7 +280,7 @@ 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 cb013d85..68945244 100644
--- a/nac3core/src/codegen/stmt.rs
+++ b/nac3core/src/codegen/stmt.rs
@@ -2,6 +2,8 @@ use super::{
     super::symbol_resolver::ValueEnum,
     expr::destructure_range,
     irrt::{handle_slice_indices, list_slice_assignment},
+    model::*,
+    structs::{cslice::CSlice, exception::Exception},
     CodeGenContext, CodeGenerator,
 };
 use crate::{
@@ -1113,47 +1115,37 @@ 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<Pointer<'ctx, StructModel<Exception<'ctx>>>>,
     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 sizet = generator.get_sizet(ctx.ctx);
+        let i32_model = NIntModel(Int32);
+        let cslice_model = StructModel(CSlice { sizet });
 
-            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.review_value(ctx.ctx, filename).unwrap();
+        pexn.gep(ctx, |f| f.filename).store(ctx, filename);
+
+        let row = i32_model.constant(ctx.ctx, loc.row as u64);
+        pexn.gep(ctx, |f| f.line).store(ctx, row);
+
+        let column = i32_model.constant(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_name).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();
 }
 
@@ -1609,35 +1601,50 @@ pub fn gen_stmt<G: CodeGenerator>(
         StmtKind::Try { .. } => gen_try(generator, ctx, stmt)?,
         StmtKind::Raise { exc, .. } => {
             if let Some(exc) = exc {
-                let exc = if let Some(v) = generator.gen_expr(ctx, exc)? {
-                    v.to_basic_value_enum(ctx, generator, exc.custom.unwrap())?
-                } else {
+                // Define all used models
+                let sizet = generator.get_sizet(ctx.ctx);
+                let pexn_model = PointerModel(StructModel(Exception { sizet }));
+
+                let Some(exn) = generator.gen_expr(ctx, exc)? else {
                     return Ok(());
                 };
-                gen_raise(generator, ctx, Some(&exc), stmt.location);
+                let pexn = exn.to_basic_value_enum(ctx, generator, ctx.primitives.exception)?;
+                let pexn = pexn_model.review_value(ctx.ctx, pexn).unwrap();
+
+                gen_raise(generator, ctx, Some(pexn), 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 {
+            // Define all used models
+            let sizet = generator.get_sizet(ctx.ctx);
+            let byte_model = NIntModel(Byte);
+            let cslice_model = StructModel(CSlice { sizet });
+
+            // Check `test`
+            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.review_value(ctx.ctx, test).unwrap(); // Python `bool`s are 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.review_value(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],