diff --git a/lang/src/alloc.asm b/lang/src/alloc.asm
index 35a327f..50f8892 100644
--- a/lang/src/alloc.asm
+++ b/lang/src/alloc.asm
@@ -15,6 +15,7 @@ extern allocate
 extern vec_init
 extern vec_push
 extern vec_get
+extern vec_try_grow_with
 
 
 global bump_init
@@ -29,14 +30,21 @@ mmap_alloc:
     pop rbp
     ret
 
+;; define-fn: fn bump_init()
 bump_init:
     push rbp
     mov rbp, rsp
 
-    lea rdi, [rel free_list]
-    mov rsi, 16
-    mov rdx, 0
-    call vec_init
+    mov rdi, 0x1000
+    call mmap_alloc
+    lea rdx, [rel free_list]
+    mov [rdx], rax
+    mov qword [rdx + 8], 0    ; size 0
+    mov rax, 0x1000
+    shr rax, 4                  ; capacity in blocks of 16 bytes
+    mov qword [rdx + 16], rax   ; capacity
+    mov qword [rdx + 24], 16    ; elem_size = 16
+    mov qword [rdx + 32], 0     ; drop = None
 
     pop rbp
     ret
@@ -50,6 +58,20 @@ bump_new_block:
     ja .mmap
     mov rdi, 4096
 .mmap:
+
+    push rdi
+
+    lea rdi, [rel free_list]
+    mov rsi, [rdi + 8]
+    mov rax, rsi
+    shr rax, 1
+    add rax, 1
+    add rsi, rax
+    mov rdx, mmap_alloc
+    call vec_try_grow_with
+
+    pop rdi
+
     ; next power of 2
     lea rax, [rdi - 1]
     lzcnt rax, rax
@@ -75,8 +97,38 @@ bump_new_block:
     pop rbp
     ret
 
+;; rdi: num
+;; rsi: multiple
+next_multiple_of:
+    test rsi, rsi
+    je .l1
+    mov rax, rdi
+    or rax, rsi
+    shr rax, 32
+    je .l2
+    mov rax, rdi
+    xor edx, edx
+    div rsi
+    jmp .l3
+.l2:
+    mov eax, edi
+    xor edx, edx
+    div esi
+.l3:
+    sub rsi, rdx
+    test rdx, rdx
+    cmove rsi, rdx
+    add rsi, rdi
+    mov rax, rsi
+    ret
+.l1:
+    mov rax, rdi
+    ret
+    
+
 ;; rdi: number of bytes to allocate
 ;; rsi: alignment
+;; define-fn:  fn bump_alloc(size: usize, alignment: usize) -> *mut u8
 bump_alloc:
     push rbp
     mov rbp, rsp
@@ -104,25 +156,21 @@ bump_alloc:
 
     ; check for space
     ; block_ptr.next_multiple_of(alignment) + size <= block_ptr + block_size
-    mov rcx, [rsp + 8]    ; alignment
-    ; let ptr = block_ptr | alignment
-    or rax, rcx                 ; align up
-    xor rdx, rdx                ; clear high qword
-    ; let rem = ptr % alignment
-    div rcx
-    ; let diff = alignment - rem
-    sub rcx, rdx
-    mov rax, [rsp + 16]          ; block+ptr
-    ; let aligned_ptr = block_ptr + diff
-    add rax, rcx
-    ; let aligned_end = aligned_ptr + size
-    add rax, [rsp]              ; size
-    ; let block_end = block_ptr + block_size
-    mov rdx, [rsp + 16]         ; block_ptr
-    add rdx, [rsp + 24]         ; block_ptr + block_size
-    ; if aligned_end <= block_end
-    cmp rax, rdx
+    mov rdi, rdx
+    mov rsi, [rsp + 8]          ; alignment
+    call next_multiple_of
+    ; rax = aligned_ptr
+
+    mov rdx, rax
+    add rdx, qword [rsp]        ; ptr + size
+    ; rdx = new_end
+
+    mov rcx, [rsp + 16]         ; block_ptr
+    add rcx, [rsp + 24]         ; block_size
+
+    cmp rdx, rcx
     jle .found_space
+
     ; else try next block
     inc r13
     jmp .alloc_loop
@@ -136,13 +184,17 @@ bump_alloc:
     dec r13
     jmp .alloc_loop
 .found_space:
-    sub rdx, rax                ; remaining size in block
-    mov r13, [rsp + 32]         ; block entry ptr
-    mov [r13], rax
-    mov rax, [rsp + 24]         ; block_size
-    sub rax, rdx
-    mov [r13 + 8], rax
-    mov rax, [r13]
+    mov r12, [rsp + 32]         ; block entry ptr
+    mov rcx, [r12]              ; block_ptr
+    mov [r12], rdx              ; update block_ptr
+
+    ; new_end - old_ptr
+    sub rdx, rcx
+
+    mov rcx, [r12 + 8]          ; block_size
+    sub rcx, rdx
+    mov [r12 + 8], rcx
+
     add rsp, 0x28
     pop r13
     pop r12
diff --git a/lang/src/vec.asm b/lang/src/vec.asm
index 5caa61d..ede801d 100644
--- a/lang/src/vec.asm
+++ b/lang/src/vec.asm
@@ -8,7 +8,7 @@ extern memswap
 extern oom
 extern panic
 extern eprint_str
-extern allocate
+extern bump_alloc
 
 global vec_init
 global vec_init_with
@@ -26,6 +26,8 @@ global vec_insert
 global vec_insert_many
 global vec_insert_sorted
 global vec_binary_search_by
+global vec_try_grow
+global vec_try_grow_with
 
 global vec_tests
 
@@ -57,7 +59,8 @@ vec_init:
     push rdi
     ; (*vec).data = allocate(INIT_CAPACITY);
     mov rdi, INIT_CAPACITY
-    call allocate
+    mov rsi, 8
+    call bump_alloc
     pop r15
     mov [r15], rax
     ; (*vec).len = 0;
@@ -94,7 +97,8 @@ vec_init_with:
     mov rax, rcx
     mul rsi                     ; capacity * item_size
     mov rdi, rax
-    call allocate
+    mov rsi, 8
+    call bump_alloc
     pop r15
     mov [r15], rax
     ; (*vec).len = 0;
@@ -339,6 +343,16 @@ vec_remove:
 ;; rsi: desired size
 ;; fn vec_try_grow(vec: *mut Vec, new_size: usize) -> bool
 vec_try_grow:
+    mov rdx, bump_alloc
+    call vec_try_grow_with
+    ret
+
+;; essentially a reserve() function
+;; rdi: pointer to Vec struct
+;; rsi: desired size
+;; rdx: allocate function pointer
+;; fn vec_try_grow(vec: *mut Vec, new_size: usize) -> bool
+vec_try_grow_with:
     push rbp
     mov rbp, rsp
     push rbx
@@ -366,7 +380,8 @@ vec_try_grow:
     mul qword [rdi + 24]   ; new_capacity * item_size
     ; new_data = allocate(new_capacity);
     mov rdi, rax
-    call allocate
+    mov rsi, 8
+    call rdx
     mov [rsp + 16], rax
     mov rdi, [rsp]
     ; memcpy(new_data, old_data, len * vec.item_size);
diff --git a/lang/tests/shared/defs.rs b/lang/tests/shared/defs.rs
index fb5b9c6..cd498d2 100644
--- a/lang/tests/shared/defs.rs
+++ b/lang/tests/shared/defs.rs
@@ -2,6 +2,8 @@
 // Auto-generated Rust bindings from assembly source
 
 unsafe extern "C" {
+    pub unsafe fn bump_init();
+    pub unsafe fn bump_alloc(size: usize, alignment: usize) -> *mut u8;
     pub unsafe fn parse_func(ast: *mut Ast) -> u64;
     pub unsafe fn parse_args(ast: *mut Ast) -> (*const u64, usize);
     pub unsafe fn parse_postfix_expr(ast: *mut Ast) -> (u64, bool);
diff --git a/lang/tests/vec.rs b/lang/tests/vec.rs
index 7159f07..a09011c 100644
--- a/lang/tests/vec.rs
+++ b/lang/tests/vec.rs
@@ -4,6 +4,9 @@ mod util;
 use util::{ffi::*, vec::Vec, BlobVec};
 
 fn main() {
+    unsafe {
+        util::defs::bump_init();
+    }
     static mut DROPS: usize = 1;
     fn get_drops() -> usize {
         unsafe { (&raw const DROPS).read() }