diff --git a/src/ast.c b/src/ast.c
index 96e1379..66f181a 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -1,7 +1,9 @@
+#include <inttypes.h>
 #include <stdio.h>
 
 #include "include/ast.h"
 #include "include/dstr.h"
+#include "include/gc.h"
 #include "include/scope.h"
 #include "include/util.h"
 
@@ -19,7 +21,7 @@ static char* asttype_names[] = {
 };
 
 AST* ast_init(ASTType type, void* data) {
-    AST* ast = malloc(sizeof(AST));
+    AST* ast = gc_alloc(sizeof(AST), GC_TYPE_AST);
 
     ast->type = type;
     ast->data = data;
@@ -62,6 +64,23 @@ void ast_destroy(AST* ast) {
     free(ast);
 }
 
+void ast_destroy_psv(AST* ast) {
+    if (!ast) return;
+
+    switch (ast->type) {
+        case AST_TYPE_NUM:   ast_num_data_destroy(ast->data); break;
+        case AST_TYPE_CALL:  ast_call_data_destroy_psv(ast->data); break;
+        case AST_TYPE_VREF:  ast_vref_data_destroy(ast->data); break;
+        case AST_TYPE_VDEF:  ast_vdef_data_destroy_psv(ast->data); break;
+        case AST_TYPE_BLOCK: ast_block_data_destroy_psv(ast->data); break;
+        case AST_TYPE_FDEF:  ast_fdef_data_destroy_psv(ast->data); break;
+        case AST_TYPE_ARG:   ast_arg_data_destroy(ast->data); break;
+        case AST_TYPE_BIF:   ast_bif_data_destroy(ast->data); break;
+        default:
+            log_dbgf("Unknown ast type %d (max: %d)", ast->type, AST_TYPE_MAX);
+    }
+}
+
 void ast_print(AST* ast) { ast_print_i(ast, 0); }
 
 void ast_print_i(AST* ast, int i) {
@@ -132,6 +151,8 @@ ASTBIFData* ast_bif_data_init(AST* fn(size_t, AST**, Scope*)) {
     return (ASTBIFData*)fn;
 }
 
+void ast_bif_data_destroy(ASTBIFData* bif) { return; }
+
 ASTCallData* ast_call_data_init(char* to, size_t argc, AST** argv) {
     talloc(ASTCallData, call);
 
@@ -152,6 +173,13 @@ void ast_call_data_destroy(ASTCallData* call) {
     free(call);
 }
 
+void ast_call_data_destroy_psv(ASTCallData* call) {
+    if (!call) return;
+    free(call->to);
+    free(call->argv);
+    free(call);
+}
+
 void ast_call_print(ASTCallData* data, int i) {
     INDENT_BEGIN(i);
 
@@ -178,6 +206,11 @@ void ast_vdef_data_destroy(ASTVDefData* vdef) {
     free(vdef);
 }
 
+void ast_vdef_data_destroy_psv(ASTVDefData* vdef) {
+    free(vdef->name);
+    free(vdef);
+}
+
 void ast_vdef_print(ASTVDefData* vdef, int depth) {
     INDENT_BEGIN(depth);
 
@@ -228,6 +261,11 @@ void ast_block_data_destroy(ASTBlockData* block) {
     free(block);
 }
 
+void ast_block_data_destroy_psv(ASTBlockData* block) {
+    free(block->inside);
+    free(block);
+}
+
 void ast_block_print(ASTBlockData* data, int depth) {
     INDENT_BEGIN(depth);
 
@@ -256,6 +294,13 @@ void ast_fdef_data_destroy(ASTFDefData* fdef) {
     ast_destroy(fdef->body);
 }
 
+void ast_fdef_data_destroy_psv(ASTFDefData* fdef) {
+    free(fdef->name);
+    free(fdef->argv);
+    free(fdef->body);
+    free(fdef);
+}
+
 void ast_fdef_print(ASTFDefData* fdef, int i) {
     INDENT_BEGIN(i)
     INDENT_TITLE("ASTFDefData", fdef);
diff --git a/src/exec.c b/src/exec.c
index 78103f8..cb51c49 100644
--- a/src/exec.c
+++ b/src/exec.c
@@ -42,7 +42,7 @@ AST* exec_start(AST* ast) {
     dlist_destroy(builtins);
     */
 
-    scope_destroy_psv(global);
+    // scope_destroy_psv(global);
     return res;
 }
 
diff --git a/src/gc.c b/src/gc.c
new file mode 100644
index 0000000..7b520a2
--- /dev/null
+++ b/src/gc.c
@@ -0,0 +1,37 @@
+#include "include/gc.h"
+#include "include/ast.h"
+#include "include/scope.h"
+#include "include/util.h"
+#include <stdio.h>
+
+#include <stddef.h>
+
+GC* gclist = NULL;
+
+void gc_destroy(GC* gc) { free(gc); }
+
+void* gc_alloc(size_t sz, GCType type) {
+    void* mem = malloc(sz);
+    GC* gc = malloc(sizeof(GC));
+
+    gc->p = mem;
+    gc->type = type;
+    gc->marked = false;
+    gc->nxt = gclist;
+    gclist = gc;
+
+    return mem;
+}
+
+void gc_hack_free() {
+    while (gclist) {
+        log_dbgf("freeing %p", gclist);
+        GC* gc = gclist;
+        gclist = gclist->nxt;
+        switch (gc->type) {
+            case GC_TYPE_AST:   ast_destroy_psv(gc->p); break;
+            case GC_TYPE_SCOPE: scope_destroy_psv(gc->p); break;
+        }
+        gc_destroy(gc);
+    }
+}
diff --git a/src/include/ast.h b/src/include/ast.h
index 5e846f8..eaff6cc 100644
--- a/src/include/ast.h
+++ b/src/include/ast.h
@@ -41,6 +41,8 @@ AST* ast_init(ASTType type, void* data);
 AST* ast_init_scope(ASTType type, void* data, Scope* scope);
 // Destroy an `AST`, recursively.
 void ast_destroy(AST* ast);
+// Destroy an `AST`.
+void ast_destroy_psv(AST* ast);
 // Print an `AST`, recursively.
 void ast_print(AST* ast);
 // Helper function to `ast_print()`, where `i` is indentation level.
@@ -73,8 +75,8 @@ typedef AST* (*ASTBIFData)(size_t argc, AST** argv, Scope* scope);
 
 // Create a built-in function.
 ASTBIFData* ast_bif_data_init(AST* fn(size_t, AST**, Scope*));
-
-// There is no `ASTBIFData` destroy function, as function pointers are immortal.
+// Destroy an `ASTBIFData`.
+void ast_bif_data_destroy(ASTBIFData* bif);
 
 // A call (to a function).
 typedef struct {
@@ -85,8 +87,10 @@ typedef struct {
 
 // Create a new `ASTCallData`.
 ASTCallData* ast_call_data_init(char* to, size_t argc, AST** argv);
-// Destroy an `ASTCallData`.
+// Destroy an `ASTCallData` recursively.
 void ast_call_data_destroy(ASTCallData* call);
+// Destroy an `ASTCallData`.
+void ast_call_data_destroy_psv(ASTCallData *call);
 // Print an `ASTCallData`.
 void ast_call_print(ASTCallData*, int i);
 
@@ -100,6 +104,8 @@ typedef struct {
 ASTVDefData* ast_vdef_data_init(char* name, AST* val);
 // Destroys the `ASTVDefData`, `ASTVDefData->name`, and `ASTVDefData->val`.
 void ast_vdef_data_destroy(ASTVDefData* vdef);
+// Destroy an `ASTVDefData`.
+void ast_vdef_data_destroy_psv(ASTVDefData* vdef);
 // Print an `ASTVDefData`.
 void ast_vdef_print(ASTVDefData*, int depth);
 
@@ -125,6 +131,8 @@ typedef struct {
 ASTBlockData* ast_block_data_init(AST** inside, size_t ln);
 // Destroy an `ASTBlockData`, recursively.
 void ast_block_data_destroy(ASTBlockData* block);
+// Destroy an `ASTBlockData`.
+void ast_block_data_destroy_psv(ASTBlockData *block);
 // Print an `ASTBlockData`.
 void ast_block_print(ASTBlockData*, int i);
 
@@ -137,8 +145,10 @@ typedef struct {
 
 // Create a new `ASTFDefData`.
 ASTFDefData* ast_fdef_data_init(char* name, size_t argc, AST** argv, AST* body);
-// Destroy an `ASTFDefData`.
+// Destroy an `ASTFDefData`, recursively.
 void ast_fdef_data_destroy(ASTFDefData* fdef);
+// Destroy an `ASTFDefData`.
+void ast_fdef_data_destroy_psv(ASTFDefData* fdef);
 // Print an `ASTFDefData`.
 void ast_fdef_print(ASTFDefData* fdef, int i);
 
diff --git a/src/include/gc.h b/src/include/gc.h
new file mode 100644
index 0000000..020719c
--- /dev/null
+++ b/src/include/gc.h
@@ -0,0 +1,31 @@
+#ifndef GC_H
+#define GC_H
+
+#include <stdlib.h>
+
+// The type a GC can refer to.
+typedef enum {
+    GC_TYPE_AST,
+    GC_TYPE_SCOPE,
+    GC_TYPE_MAX = GC_TYPE_SCOPE
+} GCType;
+
+// Added to each AST and Scope; keep track of what's actually still accessible.
+typedef struct GC_STRUCT {
+    void* p;               // Pointer to the data.
+    struct GC_STRUCT* nxt; // The next GC in the linked list.
+    GCType type;           // What type of data.
+    bool marked;           // Whether the data is still accessible.
+} GC;
+
+GC* gc_init(void* p, GCType type, GC*);
+// Does not free ->p or ->nxt.
+void gc_destroy(GC* gc);
+
+// Allocate for an object in the heap, and keep track of it in the GC.
+void* gc_alloc(size_t sz, GCType type);
+
+// Free everything, immediately.
+void gc_hack_free();
+
+#endif
diff --git a/src/include/scope.h b/src/include/scope.h
index b91490a..55e65dc 100644
--- a/src/include/scope.h
+++ b/src/include/scope.h
@@ -7,7 +7,7 @@
 typedef struct SCOPE_T {
     HTab* here; // This scope's hash table.
     struct SCOPE_T* inherit; // The scope to inherit from.
-    int uses; // How many `AST`s are linked to this scope.
+    int uses; // How many `AST`s are linked to this scope. // TODO: REMOVE.
 } Scope;
 
 // Create a new `Scope`. Creates new empty `HTab` for current scope.
diff --git a/src/main.c b/src/main.c
index f788a1d..d4499ff 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4,7 +4,7 @@
 #include "include/ast.h"
 #include "include/dstr.h"
 #include "include/exec.h"
-
+#include "include/gc.h"
 #include "include/lexer.h"
 #include "include/util.h"
 
@@ -22,8 +22,9 @@ int main(int argc, char** argv) {
         ast_print(root);
         AST* eval = exec_start(root);
         ast_print(eval);
-        ast_destroy(eval);
-        ast_destroy(root);
+        // ast_destroy(eval);
+        // ast_destroy(root);
+        gc_hack_free();
         exit(0);
     }
 
@@ -60,8 +61,9 @@ int main(int argc, char** argv) {
 
             AST* eval = exec_start(root);
             ast_print(eval);
-            ast_destroy(eval);
-            ast_destroy(root);
+            // ast_destroy(eval);
+            // ast_destroy(root);
+            gc_hack_free();
         }
 
         dstr_destroy(ln);
diff --git a/src/scope.c b/src/scope.c
index 4076e04..09b6c7c 100644
--- a/src/scope.c
+++ b/src/scope.c
@@ -1,11 +1,12 @@
 #include "include/scope.h"
+#include "include/gc.h"
 #include "include/htab.h"
 #include "include/util.h"
 #include <stdio.h>
 #include <stdlib.h>
 
 Scope* scope_init(Scope* inherit) {
-    Scope* scope = malloc(sizeof(Scope));
+    Scope* scope = gc_alloc(sizeof(Scope), GC_TYPE_SCOPE);
 
     scope->here = htab_init();
     scope->inherit = inherit;