alisp.org: mark TODOs

arena_t doesn't really make sense given we also have a free list.
Better to name it generic.

Makefile

@@ -6,20 +6,21 @@ TEST=$(DIST)/test.out
 
 LDFLAGS=
 GFLAGS=-Wall -Wextra -Wpedantic -Werror -std=c23 -I./include/
-DFLAGS=-ggdb -fsanitize=address -fsanitize=undefined -DVERBOSE_LOGS=1
+DFLAGS=-ggdb -fsanitize=address -fsanitize=undefined
 RFLAGS=-O3
 
 MODE=release
 ifeq ($(MODE), release)
 CFLAGS=$(GFLAGS) $(RFLAGS)
 else ifeq ($(MODE), debug)
-CFLAGS=$(GFLAGS) $(DFLAGS)
+CFLAGS=$(GFLAGS) $(DFLAGS) -DVERBOSE_LOGS=1
 else ifeq ($(MODE), full)
-CFLAGS=$(GFLAGS) $(DFLAGS) -DTEST_VERBOSE=1
+CFLAGS=$(GFLAGS) $(DFLAGS) -DVERBOSE_LOGS=2 -DTEST_VERBOSE=1
 endif
 
 # Units to compile
-UNITS=src/sv.c src/vec.c src/stream.c src/symtable.c src/tag.c src/lisp.c src/reader.c
+UNITS=src/sv.c src/vec.c src/stream.c src/symtable.c src/lisp.c src/allocator.c \
+		src/sys.c src/reader.c
 OBJECTS:=$(patsubst src/%.c, $(DIST)/%.o, $(UNITS))
 
 TEST_UNITS=test/main.c

alisp.org

@@ -84,7 +84,7 @@ Scheme doesn't have it.  Should we implement this?
 - Unmanaged objects are allocations we do as part of the runtime.
   These are things that we expect to have near infinite lifetimes
   (such as the symbol table, vector of allocated objects, etc).
-*** TODO Design an allocator
+*** DONE Design an allocator
 We'll need an allocator for all our managed objects.  Requirements:
 - Stable pointers (memory that has already been allocated should be
   free to utilise via the same pointer for the lifetime of the
@@ -92,14 +92,15 @@ We'll need an allocator for all our managed objects.  Requirements:
 - Able to tag allocations as unused (i.e. "free") and able to reuse
   these allocations
   - This will link into the garbage collector, which should yield a
-    sequence of objects that should be "freed".
+    sequence of objects that were previously tagged as unfree and
+    should be "freed".
 - Able to allocate all the managed types we have
-**** TODO Design allocation data structures
+**** DONE Design allocation data structures
-**** TODO Design allocation methods for different lisp types
+**** DONE Design allocation methods for different lisp types
-- Conses
-- Vectors
 - Strings (when implemented)
-**** TODO Design allocation freeing methods
+***** DONE Conses
+***** DONE Vectors
+**** DONE Design allocation freeing method
 *** TODO Design garbage collection scheme :gc:
 Really, regardless of what I do, we need to have some kind of garbage
 collection header on whatever managed objects we allocate.  We need to

include/alisp/alisp.h

@@ -8,6 +8,7 @@
 #ifndef ALISP_H
 #define ALISP_H
 
+#include <alisp/allocator.h>
 #include <alisp/base.h>
 #include <alisp/lisp.h>
 #include <alisp/reader.h>

include/alisp/allocator.h

@@ -0,0 +1,57 @@
+/* allocator.h: Lisp Allocator
+ * Created: 2026-02-12
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef ALLOCATOR_H
+#define ALLOCATOR_H
+
+#include <alisp/lisp.h>
+#include <alisp/vec.h>
+
+#define ALLOC_PAGE_DEFAULT_SIZE 512
+
+typedef struct
+{
+  u64 references;
+  tag_t tag : 8;
+} alloc_metadata_t;
+
+typedef struct
+{
+  alloc_metadata_t metadata;
+  u8 data[];
+} alloc_node_t;
+
+typedef struct
+{
+  vec_t data;
+} page_t;
+
+typedef struct
+{
+  vec_t pages;
+  vec_t free_vec;
+} alloc_t;
+
+lisp_t *alloc_make(alloc_t *, tag_t type);
+void alloc_delete(alloc_t *, lisp_t *);
+u64 alloc_cost(alloc_t *);
+void alloc_free(alloc_t *);
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

include/alisp/lisp.h

@@ -65,33 +65,7 @@ lisp_t *tag_int(const i64);
 lisp_t *tag_sym(const char *);
 lisp_t *tag_cons(const cons_t *);
 lisp_t *tag_vec(const vec_t *);
-
+lisp_t *tag_generic(void *, tag_t);
-/// System context
-typedef struct
-{
-  vec_t conses;
-  vec_t vectors;
-  u64 num_conses, num_vectors;
-} sys_mem_t;
-
-typedef struct
-{
-  sys_mem_t memory;
-  sym_table_t symtable;
-} sys_t;
-
-void sys_init(sys_t *);
-lisp_t *sys_alloc(sys_t *, tag_t type);
-void sys_free(sys_t *);
-
-// Debugging function: provides total memory usage from system.
-u64 sys_cost(sys_t *);
-
-/// Constructors and destructors
-lisp_t *make_int(i64);
-lisp_t *make_vec(sys_t *, u64);
-lisp_t *intern(sys_t *, sv_t);
-lisp_t *cons(sys_t *, lisp_t *, lisp_t *);
 
 i64 as_int(lisp_t *);
 char *as_sym(lisp_t *);
@@ -101,13 +75,9 @@ vec_t *as_vec(lisp_t *);
 #define CAR(L) (as_cons(L)->car)
 #define CDR(L) (as_cons(L)->cdr)
 
-lisp_t *car(lisp_t *);
-lisp_t *cdr(lisp_t *);
-
-void lisp_free(lisp_t *);
-void lisp_free_rec(lisp_t *);
-
 void lisp_print(FILE *, lisp_t *);
+u64 tag_sizeof(tag_t);
+u64 lisp_sizeof(lisp_t *);
 
 #endif
 

include/alisp/reader.h

@@ -8,8 +8,8 @@
 #ifndef READER_H
 #define READER_H
 
-#include <alisp/lisp.h>
 #include <alisp/stream.h>
+#include <alisp/sys.h>
 
 typedef enum
 {

include/alisp/sys.h

@@ -0,0 +1,53 @@
+/* sys.h: System context and constructors
+ * Created: 2026-02-12
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef SYS_H
+#define SYS_H
+
+#include <alisp/allocator.h>
+#include <alisp/lisp.h>
+
+/// System context
+typedef struct
+{
+  alloc_t memory;
+  sym_table_t symtable;
+} sys_t;
+
+void sys_init(sys_t *);
+lisp_t *sys_alloc(sys_t *, tag_t type);
+void sys_free(sys_t *);
+
+// Debugging function: provides total memory usage from system.
+u64 sys_cost(sys_t *);
+
+/// Constructors and general Lisp API
+lisp_t *make_int(i64);
+lisp_t *make_vec(sys_t *, u64);
+lisp_t *intern(sys_t *, sv_t);
+lisp_t *cons(sys_t *, lisp_t *, lisp_t *);
+
+lisp_t *car(lisp_t *);
+lisp_t *cdr(lisp_t *);
+
+void lisp_free(lisp_t *);
+void lisp_free_rec(lisp_t *);
+
+#endif
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

include/alisp/vec.h

@@ -36,7 +36,10 @@ void vec_init(vec_t *, u64);
 void vec_free(vec_t *);
 u8 *vec_data(vec_t *);
 
+// Append, possibly reallocating memory
 void vec_append(vec_t *, const void *const, u64);
+// Try to append without allocating memory
+bool vec_try_append(vec_t *, const void *const, u64);
 void vec_ensure_free(vec_t *, u64);
 void vec_clone(vec_t *, vec_t *);
 

src/allocator.c

@@ -0,0 +1,212 @@
+/* allocator.c: Allocator implementations
+ * Created: 2026-02-12
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <stdlib.h>
+
+#include <alisp/allocator.h>
+#include <alisp/lisp.h>
+#include <alisp/vec.h>
+#include <string.h>
+
+page_t *make_page(u64 size)
+{
+  page_t *page = calloc(1, sizeof(*page));
+  vec_init(&page->data, MAX(size, ALLOC_PAGE_DEFAULT_SIZE));
+  return page;
+}
+
+alloc_node_t *make_node(page_t *page, tag_t type)
+{
+  alloc_node_t *node = NULL;
+  u64 size           = sizeof(*node);
+  switch (type)
+  {
+  case TAG_CONS:
+    size += sizeof(cons_t);
+    break;
+  case TAG_VEC:
+    size += sizeof(vec_t);
+    break;
+  case TAG_NIL:
+  case TAG_INT:
+  case TAG_SYM:
+  default:
+    FAIL("Unreachable");
+    return node;
+  }
+
+  // We must ensure size is a multiple of 8 for alignment purposes
+  size = (size & 0b111) == 0 ? size : size + (8 - (size & 0b111));
+
+  if (!vec_try_append(&page->data, NULL, size))
+    return NULL;
+  node = (alloc_node_t *)(vec_data(&page->data) + page->data.size - size);
+  node->metadata = (alloc_metadata_t){.references = 0, .tag = type};
+  return node;
+}
+
+alloc_node_t *lisp_to_node(lisp_t *lisp)
+{
+  void *raw_ptr = NULL;
+  switch (get_tag(lisp))
+  {
+  case TAG_CONS:
+    raw_ptr = as_cons(lisp);
+    break;
+  case TAG_VEC:
+    raw_ptr = as_vec(lisp);
+    break;
+  case TAG_NIL: // These shouldn't be allocated
+  case TAG_INT:
+  case TAG_SYM:
+  default:
+    FAIL("Unreachable");
+    return NIL;
+  }
+
+  alloc_node_t *node = raw_ptr;
+  return &node[-1];
+}
+
+lisp_t *alloc_make(alloc_t *alloc, tag_t type)
+{
+  switch (type)
+  {
+  case TAG_CONS:
+  case TAG_VEC:
+    break;
+  case TAG_NIL: // These shouldn't be allocated
+  case TAG_INT:
+  case TAG_SYM:
+  default:
+    FAIL("Unreachable");
+    return NIL;
+  }
+
+  // We want to try to fill this node with an allocation of this type.
+  alloc_node_t *node = NULL;
+
+  // Try to get something from the free vector
+  u64 free_vec_size = VEC_SIZE(&alloc->free_vec, alloc_node_t *);
+  for (u64 i = 0; i < free_vec_size; ++i)
+  {
+    alloc_node_t **nodeptr = &VEC_GET(&alloc->free_vec, i, alloc_node_t *);
+
+    // Skip any nodes that don't have the right type.
+    if (nodeptr[0]->metadata.tag != type)
+      continue;
+
+    assert("Expected free node to have no references" &&
+           nodeptr[0]->metadata.references == 0);
+
+    // Pop this node off the free vector by swapping it with the last item and
+    // decrementing the size of the vector.
+
+    alloc_node_t **lastptr =
+        &VEC_GET(&alloc->free_vec, free_vec_size - 1, alloc_node_t *);
+    alloc_node_t *val = *nodeptr;
+    *nodeptr          = *lastptr;
+    *lastptr          = val;
+
+    // Decrement the size of the free vector
+    alloc->free_vec.size -= sizeof(val);
+
+    // Then use that valid (and now unused) node as our return.
+    node = *lastptr;
+
+    goto end;
+  }
+
+  // We couldn't get anything from the free vector, so try to allocate a fresh
+  // one against one of the pages.
+  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  {
+    page_t *page = VEC_GET(&alloc->pages, i, page_t *);
+    node         = make_node(page, type);
+    if (node)
+      goto end;
+  }
+
+  // There aren't any pages we can allocate against, so we need to make a new
+  // page.
+  page_t *page = make_page(0);
+  vec_append(&alloc->pages, &page, sizeof(page));
+  node = make_node(page, type);
+
+end:
+  if (!node)
+    FAIL("Unexpected issue with allocating to a verifiably good page");
+
+  return tag_generic(node->data, type);
+}
+
+void alloc_delete(alloc_t *alloc, lisp_t *lisp)
+{
+  alloc_node_t *node = lisp_to_node(lisp);
+  assert(node && node->metadata.references == 0);
+  vec_append(&alloc->free_vec, &node, sizeof(node));
+}
+
+u64 alloc_cost(alloc_t *alloc)
+{
+  u64 total_size = alloc->pages.size;
+  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  {
+    page_t *page = VEC_GET(&alloc->pages, i, page_t *);
+    total_size += page->data.size;
+  }
+  return total_size;
+}
+
+void alloc_free(alloc_t *alloc)
+{
+  for (u64 i = 0; i < VEC_SIZE(&alloc->pages, page_t *); ++i)
+  {
+    page_t *page = VEC_GET(&alloc->pages, i, page_t *);
+    // Iterate through every alloc_node in this page
+    for (u64 j = 0; j < VEC_SIZE(&page->data, u8);)
+    {
+      alloc_node_t *node = (alloc_node_t *)(vec_data(&page->data) + j);
+      u64 next           = sizeof(*node) + tag_sizeof(node->metadata.tag);
+      switch (node->metadata.tag)
+      {
+      case TAG_CONS:
+        // Do nothing - will be cleaned by overall vec free anyway
+        break;
+      case TAG_VEC:
+        vec_free((vec_t *)node->data);
+        break;
+      case TAG_NIL:
+      case TAG_INT:
+      case TAG_SYM:
+      default:
+        FAIL("Unreachable");
+      }
+      j += next;
+    }
+
+    // Each page was allocated on the heap.
+    vec_free(&page->data);
+    free(page);
+  }
+  vec_free(&alloc->pages);
+  vec_free(&alloc->free_vec);
+  memset(alloc, 0, sizeof(*alloc));
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/lisp.c

@@ -10,175 +10,82 @@
 
 #include <alisp/lisp.h>
 
-void sys_init(sys_t *sys)
+lisp_t *tag_int(i64 i)
 {
-  memset(sys, 0, sizeof(*sys));
+  return TAG((u64)i, INT);
 }
 
-lisp_t *sys_alloc(sys_t *sys, tag_t type)
+lisp_t *tag_sym(const char *str)
+{
+  return TAG((u64)str, SYM);
+}
+
+lisp_t *tag_vec(const vec_t *vec)
+{
+  return TAG((u64)vec, VEC);
+}
+
+lisp_t *tag_cons(const cons_t *cons)
+{
+  return TAG((u64)cons, CONS);
+}
+
+lisp_t *tag_generic(void *ptr, tag_t type)
 {
   switch (type)
   {
-  case TAG_CONS:
-  {
-    cons_t *cons = calloc(1, sizeof(*cons));
-    lisp_t *lisp = tag_cons(cons);
-    vec_append(&sys->memory.conses, &lisp, sizeof(&lisp));
-    sys->memory.num_conses++;
-    return lisp;
-  }
-  case TAG_VEC:
-  {
-    vec_t *vec   = calloc(1, sizeof(*vec));
-    lisp_t *lisp = tag_vec(vec);
-    vec_append(&sys->memory.vectors, &lisp, sizeof(&lisp));
-    sys->memory.num_vectors++;
-    return lisp;
-  }
-  // Shouldn't be registered
   case TAG_NIL:
+    return NIL;
   case TAG_INT:
+    return tag_int((i64)ptr);
   case TAG_SYM:
+    return tag_sym(ptr);
+  case TAG_CONS:
+    return tag_cons(ptr);
+  case TAG_VEC:
+    return tag_vec(ptr);
   default:
     FAIL("Unreachable");
-  }
     return NIL;
   }
-
-u64 sys_cost(sys_t *sys)
-{
-  u64 vec_capacity = 0;
-  for (u64 i = 0; i < sys->memory.num_vectors; ++i)
-  {
-    lisp_t *vec = VEC_GET(&sys->memory.vectors, i, lisp_t *);
-    vec_capacity += as_vec(vec)->capacity;
-  }
-  return sym_table_cost(&sys->symtable) +
-         (sys->memory.num_conses * sizeof(cons_t)) + vec_capacity;
 }
 
-void sys_free(sys_t *sys)
+tag_t get_tag(const lisp_t *lisp)
 {
-  sym_table_free(&sys->symtable);
+  static_assert(NUM_TAGS == 5);
+  if (!lisp)
+    return TAG_NIL;
+  else if (IS_TAG(lisp, INT))
+    return TAG_INT;
 
-  // Iterate through each cell of memory currently allocated and free them
+  return (u64)lisp & 0xFF;
-  for (size_t i = 0; i < VEC_SIZE(&sys->memory.conses, lisp_t **); ++i)
-  {
-    lisp_t *allocated = VEC_GET(&sys->memory.conses, i, lisp_t *);
-    lisp_free(allocated);
 }
 
-  // Iterate through each cell of memory currently allocated and free them
+i64 as_int(lisp_t *obj)
-  for (size_t i = 0; i < VEC_SIZE(&sys->memory.vectors, lisp_t **); ++i)
 {
-    lisp_t *allocated = VEC_GET(&sys->memory.vectors, i, lisp_t *);
+  assert(IS_TAG(obj, INT));
-    lisp_free(allocated);
+  u64 p_obj = (u64)obj;
+  return UNTAG(p_obj, INT) |               // Delete the tag
+         (NTH_BYTE(p_obj, 7) & 0x80) << 56 // duplicate the MSB (preserve sign)
+      ;
 }
 
-  // Free the containers
+char *as_sym(lisp_t *obj)
-  vec_free(&sys->memory.conses);
+{
-  vec_free(&sys->memory.vectors);
+  assert(IS_TAG(obj, SYM));
-
+  return (char *)UNTAG(obj, SYM);
-  // Ensure no one treats this as active in any sense
-  memset(sys, 0, sizeof(*sys));
 }
 
-lisp_t *make_int(i64 i)
+cons_t *as_cons(lisp_t *obj)
 {
-  return tag_int(i);
+  assert(IS_TAG(obj, CONS));
+  return (cons_t *)UNTAG(obj, CONS);
 }
 
-lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
+vec_t *as_vec(lisp_t *obj)
 {
-  lisp_t *cons = sys_alloc(sys, TAG_CONS);
+  assert(IS_TAG(obj, VEC));
-  CAR(cons)    = car;
+  return (vec_t *)UNTAG(obj, VEC);
-  CDR(cons)    = cdr;
-  return cons;
-}
-
-lisp_t *make_vec(sys_t *sys, u64 capacity)
-{
-  lisp_t *vec = sys_alloc(sys, TAG_VEC);
-  vec_init(as_vec(vec), capacity);
-  return vec;
-}
-
-lisp_t *intern(sys_t *sys, sv_t sv)
-{
-  const char *str = sym_table_find(&sys->symtable, sv);
-  return tag_sym(str);
-}
-
-lisp_t *car(lisp_t *lsp)
-{
-  if (!IS_TAG(lsp, CONS))
-    return NIL;
-  else
-    return CAR(lsp);
-}
-
-lisp_t *cdr(lisp_t *lsp)
-{
-  if (!IS_TAG(lsp, CONS))
-    return NIL;
-  else
-    return CDR(lsp);
-}
-
-void lisp_free(lisp_t *item)
-{
-  switch (get_tag(item))
-  {
-  case TAG_CONS:
-    // Delete the cons
-    free(as_cons(item));
-    break;
-  case TAG_VEC:
-  {
-    vec_t *vec = as_vec(item);
-    vec_free(vec);
-    free(vec);
-    break;
-  }
-  case TAG_NIL:
-  case TAG_INT:
-  case TAG_SYM:
-  case NUM_TAGS:
-    // shouldn't be dealt with (either constant or dealt with elsewhere)
-    break;
-  }
-}
-
-void lisp_free_rec(lisp_t *item)
-{
-  switch (get_tag(item))
-  {
-  case TAG_CONS:
-  {
-    lisp_free_rec(car(item));
-    lisp_free_rec(cdr(item));
-    free(as_cons(item));
-    break;
-  }
-  case TAG_VEC:
-  {
-    vec_t *vec = as_vec(item);
-    for (size_t i = 0; i < VEC_SIZE(vec, lisp_t **); ++i)
-    {
-      lisp_t *allocated = VEC_GET(vec, i, lisp_t *);
-      lisp_free_rec(allocated);
-    }
-    vec_free(vec);
-    free(vec);
-    break;
-  }
-  case TAG_NIL:
-  case TAG_INT:
-  case TAG_SYM:
-  case NUM_TAGS:
-    // shouldn't be dealt with (either constant or dealt with elsewhere)
-    break;
-  }
 }
 
 void lisp_print(FILE *fp, lisp_t *lisp)
@@ -191,26 +98,26 @@ void lisp_print(FILE *fp, lisp_t *lisp)
     fprintf(fp, "NIL");
     break;
   case TAG_INT:
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "INT[");
 #endif
     fprintf(fp, "%ld", as_int(lisp));
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #endif
     break;
   case TAG_SYM:
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "SYM[");
 #endif
     fprintf(fp, "%s", as_sym(lisp));
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #endif
     break;
   case TAG_CONS:
   {
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "LIST[");
 #else
     fprintf(fp, "(");
@@ -238,7 +145,7 @@ void lisp_print(FILE *fp, lisp_t *lisp)
         break;
       }
     }
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #else
     fprintf(fp, ")");
@@ -247,7 +154,7 @@ void lisp_print(FILE *fp, lisp_t *lisp)
   }
   case TAG_VEC:
   {
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "VEC[");
 #else
     fprintf(fp, "[");
@@ -264,7 +171,7 @@ void lisp_print(FILE *fp, lisp_t *lisp)
       }
     }
 
-#if VERBOSE_LOGS
+#if VERBOSE_LOGS == 2
     fprintf(fp, "]");
 #else
     fprintf(fp, "]");
@@ -278,6 +185,31 @@ void lisp_print(FILE *fp, lisp_t *lisp)
   }
 }
 
+u64 tag_sizeof(tag_t tag)
+{
+  switch (tag)
+  {
+  case TAG_NIL:
+    return 0;
+  case TAG_INT:
+  case TAG_SYM:
+    return sizeof(lisp_t *);
+  case TAG_CONS:
+    return sizeof(cons_t);
+  case TAG_VEC:
+    return sizeof(vec_t);
+  case NUM_TAGS:
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+u64 lisp_sizeof(lisp_t *lisp)
+{
+  return tag_sizeof(get_tag(lisp));
+}
+
 /* Copyright (C) 2025, 2026 Aryadev Chavali
 
  * This program is distributed in the hope that it will be useful, but WITHOUT

src/sys.c

@@ -0,0 +1,156 @@
+/* sys.c: System implementation
+ * Created: 2026-02-12
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <alisp/sys.h>
+
+void sys_init(sys_t *sys)
+{
+  memset(sys, 0, sizeof(*sys));
+}
+
+lisp_t *sys_alloc(sys_t *sys, tag_t type)
+{
+  switch (type)
+  {
+  case TAG_CONS:
+  case TAG_VEC:
+    return alloc_make(&sys->memory, type);
+  // Shouldn't be allocated
+  case TAG_NIL:
+  case TAG_INT:
+  case TAG_SYM:
+  default:
+    FAIL("Unreachable");
+  }
+  return NIL;
+}
+
+u64 sys_cost(sys_t *sys)
+{
+  return alloc_cost(&sys->memory) + sym_table_cost(&sys->symtable);
+}
+
+void sys_free(sys_t *sys)
+{
+  sym_table_free(&sys->symtable);
+  alloc_free(&sys->memory);
+  memset(sys, 0, sizeof(*sys));
+}
+
+lisp_t *make_int(i64 i)
+{
+  return tag_int(i);
+}
+
+lisp_t *cons(sys_t *sys, lisp_t *car, lisp_t *cdr)
+{
+  lisp_t *cons = sys_alloc(sys, TAG_CONS);
+  CAR(cons)    = car;
+  CDR(cons)    = cdr;
+  return cons;
+}
+
+lisp_t *make_vec(sys_t *sys, u64 capacity)
+{
+  lisp_t *vec = sys_alloc(sys, TAG_VEC);
+  vec_init(as_vec(vec), capacity);
+  return vec;
+}
+
+lisp_t *intern(sys_t *sys, sv_t sv)
+{
+  const char *str = sym_table_find(&sys->symtable, sv);
+  return tag_sym(str);
+}
+
+lisp_t *car(lisp_t *lsp)
+{
+  if (!IS_TAG(lsp, CONS))
+    return NIL;
+  else
+    return CAR(lsp);
+}
+
+lisp_t *cdr(lisp_t *lsp)
+{
+  if (!IS_TAG(lsp, CONS))
+    return NIL;
+  else
+    return CDR(lsp);
+}
+
+void lisp_free(lisp_t *item)
+{
+  switch (get_tag(item))
+  {
+  case TAG_CONS:
+    // Delete the cons
+    free(as_cons(item));
+    break;
+  case TAG_VEC:
+  {
+    vec_t *vec = as_vec(item);
+    vec_free(vec);
+    free(vec);
+    break;
+  }
+  case TAG_NIL:
+  case TAG_INT:
+  case TAG_SYM:
+  case NUM_TAGS:
+    // shouldn't be dealt with (either constant or dealt with elsewhere)
+    break;
+  }
+}
+
+void lisp_free_rec(lisp_t *item)
+{
+  switch (get_tag(item))
+  {
+  case TAG_CONS:
+  {
+    lisp_free_rec(car(item));
+    lisp_free_rec(cdr(item));
+    free(as_cons(item));
+    break;
+  }
+  case TAG_VEC:
+  {
+    vec_t *vec = as_vec(item);
+    for (size_t i = 0; i < VEC_SIZE(vec, lisp_t **); ++i)
+    {
+      lisp_t *allocated = VEC_GET(vec, i, lisp_t *);
+      lisp_free_rec(allocated);
+    }
+    vec_free(vec);
+    free(vec);
+    break;
+  }
+  case TAG_NIL:
+  case TAG_INT:
+  case TAG_SYM:
+  case NUM_TAGS:
+    // shouldn't be dealt with (either constant or dealt with elsewhere)
+    break;
+  }
+}
+
+/* Copyright (C) 2026 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/tag.c

@@ -1,82 +0,0 @@
-/* tag.c: Pointer tagging
- * Created: 2025-08-19
- * Author: Aryadev Chavali
- * License: See end of file
- * Commentary:
- */
-
-#include <assert.h>
-#include <stdlib.h>
-
-#include <alisp/lisp.h>
-
-lisp_t *tag_int(i64 i)
-{
-  return TAG((u64)i, INT);
-}
-
-lisp_t *tag_sym(const char *str)
-{
-  return TAG((u64)str, SYM);
-}
-
-lisp_t *tag_vec(const vec_t *vec)
-{
-  return TAG((u64)vec, VEC);
-}
-
-lisp_t *tag_cons(const cons_t *cons)
-{
-  return TAG((u64)cons, CONS);
-}
-
-tag_t get_tag(const lisp_t *lisp)
-{
-  static_assert(NUM_TAGS == 5);
-  if (!lisp)
-    return TAG_NIL;
-  else if (IS_TAG(lisp, INT))
-    return TAG_INT;
-
-  return (u64)lisp & 0xFF;
-}
-
-i64 as_int(lisp_t *obj)
-{
-  assert(IS_TAG(obj, INT));
-  u64 p_obj = (u64)obj;
-  return UNTAG(p_obj, INT) |               // Delete the tag
-         (NTH_BYTE(p_obj, 7) & 0x80) << 56 // duplicate the MSB (preserve sign)
-      ;
-}
-
-char *as_sym(lisp_t *obj)
-{
-  assert(IS_TAG(obj, SYM));
-  return (char *)UNTAG(obj, SYM);
-}
-
-cons_t *as_cons(lisp_t *obj)
-{
-  assert(IS_TAG(obj, CONS));
-  return (cons_t *)UNTAG(obj, CONS);
-}
-
-vec_t *as_vec(lisp_t *obj)
-{
-  assert(IS_TAG(obj, VEC));
-  return (vec_t *)UNTAG(obj, VEC);
-}
-
-/* Copyright (C) 2025, 2026 Aryadev Chavali
-
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
- * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
- * details.
-
- * You may distribute and modify this code under the terms of the GNU General
- * Public License Version 2, which you should have received a copy of along with
- * this program.  If not, please go to <https://www.gnu.org/licenses/>.
-
- */

src/vec.c

@@ -81,10 +81,24 @@ void vec_append(vec_t *vec, const void *const ptr, u64 size)
   if (!vec)
     return;
   vec_ensure_free(vec, size);
+  if (ptr)
     memcpy(vec_data(vec) + vec->size, ptr, size);
   vec->size += size;
 }
 
+bool vec_try_append(vec_t *vec, const void *const ptr, u64 size)
+{
+  if (!vec || vec->capacity - vec->size < size)
+    return false;
+  if (ptr)
+  {
+    void *newptr = vec_data(vec) + vec->size;
+    memcpy(newptr, ptr, size);
+  }
+  vec->size += size;
+  return true;
+}
+
 void vec_clone(vec_t *dest, vec_t *src)
 {
   if (!src || !dest)

test/test_stream.c

@@ -54,7 +54,7 @@ void stream_test_prologue(void)
 
 void stream_test_epilogue(void)
 {
-  TEST_INFO("Freeing resources and deleting file `%s`\n", valid_filename);
+  TEST_INFO("Deleting file `%s`\n", valid_filename);
   assert(valid_fp);
   fclose(valid_fp);
   remove(valid_filename);