alloc: arena_t -> alloc_t

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

Makefile

@@ -19,7 +19,8 @@ CFLAGS=$(GFLAGS) $(DFLAGS) -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

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_list;
+} 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 *);
-
-/// 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 *);
+lisp_t *tag_generic(void *, tag_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 +1,206 @@
+/* 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_metadata_t *data = raw_ptr;
+  return (alloc_node_t *)(&data[-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_list.
+  u64 free_list_size = VEC_SIZE(&alloc->free_list, alloc_node_t *);
+  for (u64 i = 0; i < free_list_size; ++i)
+  {
+    alloc_node_t **nodeptr = &VEC_GET(&alloc->free_list, i, alloc_node_t *);
+    if (nodeptr[0]->metadata.tag != type)
+      continue;
+
+    // Swap this node with the last item of the free_list
+    alloc_node_t **lastptr =
+        &VEC_GET(&alloc->free_list, free_list_size - 1, alloc_node_t *);
+
+    alloc_node_t *val = *lastptr;
+    *nodeptr          = *lastptr;
+    *lastptr          = val;
+
+    // Decrement the size of the free list
+    alloc->free_list.size -= sizeof(val);
+
+    // Get the valid node and goto the end.
+    node = *lastptr;
+
+    goto end;
+  }
+
+  // We couldn't get anything from the free list, 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_list, &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_list);
+  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)
-{
-  sym_table_free(&sys->symtable);
-
-  // Iterate through each cell of memory currently allocated and free them
-  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
-  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 *);
-    lisp_free(allocated);
-  }
-
-  // Free the containers
-  vec_free(&sys->memory.conses);
-  vec_free(&sys->memory.vectors);
-
-  // Ensure no one treats this as active in any sense
-  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)
+tag_t get_tag(const lisp_t *lisp)
 {
-  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;
-  }
+  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);
 }
 
 void lisp_print(FILE *fp, lisp_t *lisp)
@@ -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 registered
+  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);
-  memcpy(vec_data(vec) + vec->size, ptr, 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)