diff --git a/nac3core/src/codegen/mod.rs b/nac3core/src/codegen/mod.rs
index 85b963bb..715ef6d4 100644
--- a/nac3core/src/codegen/mod.rs
+++ b/nac3core/src/codegen/mod.rs
@@ -44,6 +44,7 @@ pub mod llvm_intrinsics;
 pub mod model;
 pub mod numpy;
 pub mod stmt;
+pub mod structs;
 
 #[cfg(test)]
 mod test;
diff --git a/nac3core/src/codegen/structs/cslice.rs b/nac3core/src/codegen/structs/cslice.rs
new file mode 100644
index 00000000..38e177bb
--- /dev/null
+++ b/nac3core/src/codegen/structs/cslice.rs
@@ -0,0 +1,50 @@
+use crate::codegen::{model::*, CodeGenContext};
+
+/// Fields of [`CSlice<'ctx>`].
+pub struct CSliceFields<'ctx> {
+    /// Pointer to the data.
+    pub base: Field<PointerModel<ByteModel>>,
+    /// Number of bytes of the data.
+    pub len: Field<SizeTModel<'ctx>>,
+}
+
+/// 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, PartialEq, Eq)]
+pub struct CSlice<'ctx> {
+    pub sizet: SizeTModel<'ctx>,
+}
+
+impl<'ctx> StructKind<'ctx> for CSlice<'ctx> {
+    type Fields = CSliceFields<'ctx>;
+
+    fn struct_name(&self) -> &'static str {
+        "CSlice"
+    }
+
+    fn build_fields(&self, builder: &mut FieldBuilder<'ctx>) -> Self::Fields {
+        Self::Fields {
+            base: builder.add_field_auto("content"),
+            len: builder.add_field("length", self.sizet),
+        }
+    }
+}
+
+impl<'ctx> StructModel<CSlice<'ctx>> {
+    /// Create a [`CSlice`].
+    ///
+    /// `base` and `len` must be LLVM global constants.
+    pub fn create_const(
+        &self,
+        ctx: &CodeGenContext<'ctx, '_>,
+        base: Pointer<'ctx, ByteModel>,
+        len: SizeT<'ctx>,
+    ) -> Struct<'ctx, CSlice<'ctx>> {
+        let value = self
+            .get_struct_type(ctx.ctx)
+            .const_named_struct(&[base.value.into(), len.value.into()]);
+        self.believe_value(value)
+    }
+}
diff --git a/nac3core/src/codegen/structs/exception.rs b/nac3core/src/codegen/structs/exception.rs
new file mode 100644
index 00000000..62cc3812
--- /dev/null
+++ b/nac3core/src/codegen/structs/exception.rs
@@ -0,0 +1,78 @@
+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<'ctx> {
+    /// nac3core's ID of the exception
+    pub exception_id: Field<NIntModel<ExceptionId>>,
+    /// The name of the file this `Exception` was raised in.
+    pub filename: Field<StructModel<CSlice<'ctx>>>,
+    /// The line number in the file this `Exception` was raised in.
+    pub line: Field<NIntModel<Int32>>,
+    /// The column number in the file this `Exception` was raised in.
+    pub column: Field<NIntModel<Int32>>,
+    /// The name of the Python function this `Exception` was raised in.
+    pub function_name: Field<StructModel<CSlice<'ctx>>>,
+    /// 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 message: Field<StructModel<CSlice<'ctx>>>,
+    pub params: [Field<NIntModel<Int64>>; 3],
+}
+
+/// nac3core & ARTIQ's Exception
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Exception<'ctx> {
+    /// The `SizeT` type of this string.
+    pub sizet: SizeTModel<'ctx>,
+}
+
+impl<'ctx> StructKind<'ctx> for Exception<'ctx> {
+    type Fields = ExceptionFields<'ctx>;
+
+    fn struct_name(&self) -> &'static str {
+        "Exception"
+    }
+
+    fn build_fields(&self, builder: &mut FieldBuilder<'ctx>) -> Self::Fields {
+        let str = StructModel(CSlice { sizet: self.sizet });
+
+        let exception_id = builder.add_field_auto("exception_id");
+        let file_name = builder.add_field("file_name", str);
+        let line = builder.add_field_auto("line");
+        let column = builder.add_field_auto("column");
+        let function_name = builder.add_field("function_name", str);
+        let message = builder.add_field("message", str);
+        let params = [
+            builder.add_field_auto("param0"),
+            builder.add_field_auto("param1"),
+            builder.add_field_auto("param2"),
+        ];
+
+        Self::Fields {
+            exception_id,
+            filename: file_name,
+            line,
+            column,
+            function_name,
+            message,
+            params,
+        }
+    }
+}
diff --git a/nac3core/src/codegen/structs/mod.rs b/nac3core/src/codegen/structs/mod.rs
new file mode 100644
index 00000000..14b596fb
--- /dev/null
+++ b/nac3core/src/codegen/structs/mod.rs
@@ -0,0 +1,2 @@
+pub mod cslice;
+pub mod exception;