diff --git a/lang/libcompiler/.cargo/config.toml b/lang/libcompiler/.cargo/config.toml
new file mode 100644
index 0000000..da06a0a
--- /dev/null
+++ b/lang/libcompiler/.cargo/config.toml
@@ -0,0 +1,25 @@
+[target.x86_64-unknown-linux-gnu]
+linker = "clang"
+rustflags = [
+  # LLD linker
+  #
+  # You may need to install it:
+  #
+  # - Ubuntu: `sudo apt-get install lld clang`
+  # - Fedora: `sudo dnf install lld clang`
+  # - Arch: `sudo pacman -S lld clang`
+  # "-Clink-arg=-fuse-ld=lld",
+
+  # Mold linker
+  #
+  # You may need to install it:
+  #
+  # - Ubuntu: `sudo apt-get install mold clang`
+  # - Fedora: `sudo dnf install mold clang`
+  # - Arch: `sudo pacman -S mold clang`
+  "-Clink-arg=-fuse-ld=mold",
+
+  # Nightly
+  # "-Zshare-generics=y",
+  # "-Zthreads=0",
+]
\ No newline at end of file
diff --git a/lang/libcompiler/build.rs b/lang/libcompiler/build.rs
index eeb4729..922e2a9 100644
--- a/lang/libcompiler/build.rs
+++ b/lang/libcompiler/build.rs
@@ -30,41 +30,42 @@ fn main() {
 
     println!("cargo:rustc-link-search=native={}", out_dir.display());
     let working_dir = manifest_dir.parent().unwrap();
-    for file in assembly_files.iter().map(|f| Path::new(f)) {
+    for file in assembly_files.iter().map(Path::new) {
         let path = working_dir.join(file);
         let obj = file.with_extension("o").file_name().unwrap().to_owned();
-        let lib = format!("lib{}.a", file.file_stem().unwrap().to_str().unwrap());
+        let obj_path = out_dir.join(&obj);
         std::process::Command::new("nasm")
             .current_dir(working_dir)
             .arg(path)
+            .arg("-wreloc-abs")
             .arg("-g")
             .arg("-f")
             .arg("elf64")
             .arg("-o")
-            .arg(out_dir.join(&obj))
+            .arg(&obj_path)
             .status()
             .expect("Failed to assemble assembly files");
-        std::process::Command::new("ar")
-            .current_dir(working_dir)
-            .arg("crs")
-            .arg(out_dir.join(lib))
-            .arg(out_dir.join(obj))
-            .status()
-            .expect("Failed to create static library from object files");
-        println!(
-            "cargo:rustc-link-lib=static={}",
-            file.file_stem().unwrap().to_str().unwrap()
-        );
+        println!("cargo:rustc-link-arg={}", obj_path.display());
+        // let _lib = format!("lib{}.a", file.file_stem().unwrap().to_str().unwrap());
+        // std::process::Command::new("ar")
+        //     .current_dir(working_dir)
+        //     .arg("crs")
+        //     .arg(out_dir.join(lib))
+        //     .arg(out_dir.join(obj))
+        //     .status()
+        //     .expect("Failed to create static library from object files");
+        // println!(
+        //     "cargo:rustc-link-lib=static={}",
+        //     file.file_stem().unwrap().to_str().unwrap()
+        // );
     }
 
-
     std::process::Command::new("../tools/asm2rust")
         .current_dir(working_dir)
-        .args(&assembly_files)
-        .args(&include_files)
+        .args(assembly_files)
+        .args(include_files)
         .arg("-o")
-        .arg(out_dir
-        .join("bindings.rs")
-)
-        .status().expect("Failed to generate Rust bindings from assembly files");
+        .arg(out_dir.join("bindings.rs"))
+        .status()
+        .expect("Failed to generate Rust bindings from assembly files");
 }
diff --git a/lang/libcompiler/src/lib.rs b/lang/libcompiler/src/lib.rs
index f8e5568..2896919 100644
--- a/lang/libcompiler/src/lib.rs
+++ b/lang/libcompiler/src/lib.rs
@@ -1,4 +1,7 @@
-#![feature(debug_closure_helpers)]
+#![feature(debug_closure_helpers, box_as_ptr, allocator_api)]
+
+#[cfg(test)]
+mod tests;
 
 pub mod ffi {
     #![allow(
@@ -12,14 +15,14 @@ pub mod ffi {
 }
 
 #[repr(C)]
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
 pub struct FFISlice {
     pub ptr: *const u8,
     pub len: usize,
 }
 
 #[repr(transparent)]
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
 pub struct MaybeFFISlice {
     inner: FFISlice,
 }
@@ -40,20 +43,27 @@ impl MaybeFFISlice {
 
 impl FFISlice {
     /// # Safety
-    /// The caller must ensure that the slice is valid for type T.
-    pub unsafe fn as_slice<T: Sized>(&self) -> &[T] {
+    /// The caller must ensure that the slice is valid for type T, and lasts for 'a.
+    pub unsafe fn as_slice_unchecked<'a, T: Sized>(self) -> &'a [T] {
         // SAFETY: The caller ensures that the FFISlice is valid for type T.
         unsafe { core::slice::from_raw_parts(self.ptr.cast(), self.len) }
     }
-    pub fn as_bytes(&self) -> &[u8] {
+
+    /// # Safety
+    /// The caller ensures that the slice is valid byte slice.
+    /// Namely, the pointer must be well-aligned and point to `len` bytes, and
+    /// must last for at least 'a.
+    pub fn as_u8s_unchecked<'a>(self) -> &'a [u8] {
         // SAFETY: The FFISlice is guaranteed to be a valid byte slice.
-        unsafe { core::slice::from_raw_parts(self.ptr, self.len) }
+        unsafe { self.as_slice_unchecked() }
     }
     /// # Safety
     /// The caller must ensure that the slice is a valid utf8 string.
-    pub unsafe fn as_str(&self) -> &str {
+    /// Furthermore, the pointer must be well-aligned, point to `len` bytes, and
+    /// must last for at least 'a.
+    pub unsafe fn as_str_unchecked<'a>(self) -> &'a str {
         // SAFETY: The caller ensures that the FFISlice is a valid utf8 string.
-        unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
+        unsafe { core::str::from_utf8_unchecked(self.as_u8s_unchecked()) }
     }
 }
 
@@ -610,3 +620,11 @@ mod display {
 }
 
 pub use display::{Displayed, DisplayedSliceExt};
+
+impl Default for ffi::Ast {
+    fn default() -> Self {
+        ffi::Ast {
+            nodes: vec::Vec::default(),
+        }
+    }
+}
diff --git a/lang/src/alloc.asm b/lang/src/alloc.asm
index 50f8892..0446d78 100644
--- a/lang/src/alloc.asm
+++ b/lang/src/alloc.asm
@@ -1,6 +1,6 @@
 default rel
 
-section .bss
+section .data
 align 8
 free_list: resb 40
 
@@ -67,7 +67,7 @@ bump_new_block:
     shr rax, 1
     add rax, 1
     add rsi, rax
-    mov rdx, mmap_alloc
+    lea rdx, [rel mmap_alloc]
     call vec_try_grow_with
 
     pop rdi
@@ -141,6 +141,8 @@ bump_alloc:
     lea rdi, [rel free_list]
     mov r12, [rdi + 8]
     xor r13, r13
+    cmp qword [rdi + 0], 0
+    je .init
 .alloc_loop:
     cmp r13, r12
     jae .no_block
@@ -183,6 +185,11 @@ bump_alloc:
     mov r12, r13
     dec r13
     jmp .alloc_loop
+.init:
+    call bump_init
+    mov rdi, [rsp]      ; size
+    call bump_new_block
+    jmp .alloc_loop
 .found_space:
     mov r12, [rsp + 32]         ; block entry ptr
     mov rcx, [r12]              ; block_ptr
diff --git a/lang/src/int_to_str.asm b/lang/src/int_to_str.asm
index 39b3e8a..b8b3c58 100644
--- a/lang/src/int_to_str.asm
+++ b/lang/src/int_to_str.asm
@@ -6,7 +6,7 @@ global str_to_int
 ;; rdi: pointer to input string
 ;; rsi: length of input string
 ;; dl: radix
-;; fn str_to_int(s: *const u8, len: usize, radix: u8) -> i64
+;; define-fn: str_to_int(s: *const u8, len: usize, radix: u8) -> i64
 str_to_int:
     push rbp
     mov rbp, rsp
@@ -73,7 +73,7 @@ str_to_int:
 ;; rsi: pointer to output buffer (at least 21 bytes)
 ;; rdx: length of buffer
 ;; cl: radix
-;; fn int_to_str2(value: i64, buffer: *mut u8, len: usize, radix: u8) -> (*mut u8, usize)
+;; define-fn: int_to_str2(value: i64, buffer: *mut u8, len: usize, radix: u8) -> FFISlice 
 int_to_str2:
     push rbp
     mov rbp, rsp
diff --git a/lang/src/tokeniser.asm b/lang/src/tokeniser.asm
index ad6273a..cc666e2 100644
--- a/lang/src/tokeniser.asm
+++ b/lang/src/tokeniser.asm
@@ -1,3 +1,5 @@
+default rel
+
 section .text
 extern panic
 extern strlen
@@ -143,8 +145,8 @@ global NUM_LEXEMES
 
 section .text
 ;; rdi: length of previously matched lexeme
-;; returns the length of the ident
-;; fn is_ident(lexeme_len: usize) -> usize
+;; returns the length of the ident, or 0 if not an ident
+;; define-fn: is_ident(lexeme_len: usize) -> usize
 is_ident:
     push rbp
     mov rbp, rsp
@@ -376,8 +378,15 @@ skip_whitespaces:
     ret
 
 
+;; start-structs
+;; struct RawLexeme {
+;;   token: u8,
+;;   slice: FFISlice,
+;; }
+;;
+;; end-structs
 ;; rdi: pointer to out-struct
-;; fn find_lexeme() -> (u8, *const u8, usize)
+;; define-fn: find_lexeme() -> RawLexeme 
 find_lexeme:
     push rbp
     mov rbp, rsp
@@ -523,7 +532,11 @@ find_lexeme:
     mov [rdi + 16], rax
     jmp .epilogue
 
+;; ```rust
+;;  use crate::MaybeFFISlice;
+;; ```
 ;; dil: expected token
+;; define-fn: fn expect_token(expected: u8) -> MaybeFFISlice
 expect_token:
     push rbp
     mov rbp, rsp
@@ -552,6 +565,7 @@ expect_token:
     
 ;; Returns the next token if it matches the expected token, else panics
 ;; dil: expected token
+;; define-fn: fn unwrap_token(expected: u8) -> FFISlice
 unwrap_token:
     push rbp
     mov rbp, rsp
@@ -566,6 +580,7 @@ unwrap_token:
 ;; returns 0 if token not found, else returns lexeme (ptr, len)
 ;; doesn't advance the cursor
 ;; dil: expected token
+;; define-fn: fn peek_expect_token(expected: u8) -> MaybeFFISlice
 peek_expect_token:
     push rbp
     mov rbp, rsp
@@ -579,6 +594,7 @@ peek_expect_token:
 
 ;; returns the next lexeme without advancing the cursor
 ;; rdi: out-struct pointer
+;; define-fn: fn peek_lexeme() -> RawLexeme
 peek_lexeme:
     push rbp
     mov rbp, rsp
@@ -593,6 +609,7 @@ peek_lexeme:
     ret
 
 ;; Skips one token ahead, without returning it.
+;; define-fn: fn skip_token()
 skip_token:
     push rbp
     mov rbp, rsp
@@ -603,6 +620,7 @@ skip_token:
     add rsp, 24
     pop rbp
 
+;; define-fn: fn tokeniser_get_cursor() -> usize
 tokeniser_get_cursor:
     mov rax, [rel cursor]
     ret
diff --git a/lang/src/vec.asm b/lang/src/vec.asm
index e2cd6d3..f32f28b 100644
--- a/lang/src/vec.asm
+++ b/lang/src/vec.asm
@@ -345,7 +345,7 @@ vec_remove:
 ;; rsi: desired size
 ;; define-fn: fn vec_try_grow(vec: *mut BlobVec, new_size: usize) -> bool
 vec_try_grow:
-    mov rdx, bump_alloc
+    lea rdx, [rel bump_alloc]
     call vec_try_grow_with
     ret