diff --git a/docs/State-of-play.md b/docs/State-of-play.md
index 8ebf29c..2faad50 100644
--- a/docs/State-of-play.md
+++ b/docs/State-of-play.md
@@ -9,7 +9,7 @@ and over the past few days I've logged four issues that I've tagged
 These are:
 
 * 17: [Add readtables; implement quote and keyword through readtables.](https://git.journeyman.cc/simon/post-scarcity/issues/17)
-* 18: [Consider converting from `char32_t` to `char32_t`, everywhere.](https://git.journeyman.cc/simon/post-scarcity/issues/18)
+* 18: [Consider converting from `wchar_t` to `char32_t`, everywhere.](https://git.journeyman.cc/simon/post-scarcity/issues/18)
 * 20: [Environment in stack frame.](https://git.journeyman.cc/simon/post-scarcity/issues/20)
 * 21: [Temporary objects in a function must be bound to a locals slot in the stack frame](https://git.journeyman.cc/simon/post-scarcity/issues/21)
 
diff --git a/src/c/debug.h b/src/c/debug.h
index 2c4f3d0..4c3a8b3 100644
--- a/src/c/debug.h
+++ b/src/c/debug.h
@@ -104,7 +104,7 @@
  */
 extern int verbosity;
 
-void debug_print( char32_t *message, int level, int indent );
+void debug_print( char32_t * message, int level, int indent );
 
 void debug_print_object( struct pso_pointer object, int level, int indent );
 
@@ -114,6 +114,6 @@ void debug_print_128bit( __int128_t n, int level );
 
 void debug_println( int level );
 
-void debug_printf( int level, int indent, char32_t *format, ... );
+void debug_printf( int level, int indent, char32_t * format, ... );
 
 #endif
diff --git a/src/c/io/io.c b/src/c/io/io.c
index 3d4de7c..db69b73 100644
--- a/src/c/io/io.c
+++ b/src/c/io/io.c
@@ -150,9 +150,9 @@ int initialise_io(  ) {
 }
 
 struct pso_pointer initialise_default_streams( struct pso_pointer env ) {
-	// todo: issue #21: should this have stack frame passed in?
-	// It's called in initialisation before everything else is set
-	// up, so **possibly** not?
+    // todo: issue #21: should this have stack frame passed in?
+    // It's called in initialisation before everything else is set
+    // up, so **possibly** not?
     lisp_io_in = c_string_to_lisp_symbol( C_IO_IN );
     lisp_io_out = c_string_to_lisp_symbol( C_IO_OUT );
     lisp_io_log = c_string_to_lisp_symbol( C_IO_LOG );
@@ -168,11 +168,11 @@ struct pso_pointer initialise_default_streams( struct pso_pointer env ) {
 
     lisp_stdin = lock_object( make_read_stream( file_to_url_file( stdin ),
                                                 make_cons( make_cons
-                                                        ( c_string_to_lisp_keyword
-                                                          ( L"url" ),
-                                                          c_string_to_lisp_string
-                                                          ( L"::system:standard-input" ) ),
-                                                        nil ) ) );
+                                                           ( c_string_to_lisp_keyword
+                                                             ( L"url" ),
+                                                             c_string_to_lisp_string
+                                                             ( L"::system:standard-input" ) ),
+                                                           nil ) ) );
 
     env = c_bind( lisp_io_in, lisp_stdin, env );
 
@@ -183,10 +183,10 @@ struct pso_pointer initialise_default_streams( struct pso_pointer env ) {
             lock_object( make_write_stream
                          ( file_to_url_file( stdout ),
                            make_cons( make_cons
-                                   ( c_string_to_lisp_keyword( L"url" ),
-                                     c_string_to_lisp_string
-                                     ( L"::system:standard-output" ) ),
-                                   nil ) ) );
+                                      ( c_string_to_lisp_keyword( L"url" ),
+                                        c_string_to_lisp_string
+                                        ( L"::system:standard-output" ) ),
+                                      nil ) ) );
 
         env = c_bind( lisp_io_out, lisp_stdout, env );
     }
@@ -196,10 +196,10 @@ struct pso_pointer initialise_default_streams( struct pso_pointer env ) {
             lock_object( make_write_stream
                          ( file_to_url_file( stderr ),
                            make_cons( make_cons
-                                   ( c_string_to_lisp_keyword( L"url" ),
-                                     c_string_to_lisp_string
-                                     ( L"::system:standard-output" ) ),
-                                   nil ) ) );
+                                      ( c_string_to_lisp_keyword( L"url" ),
+                                        c_string_to_lisp_string
+                                        ( L"::system:standard-output" ) ),
+                                      nil ) ) );
 
         env = c_bind( lisp_io_log, lisp_stderr, env );
     }
@@ -420,29 +420,29 @@ struct pso_pointer lisp_close( struct pso_pointer frame_pointer,
 
 struct pso_pointer add_meta_integer( struct pso_pointer meta, char32_t *key,
                                      long int value ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     return
         make_cons( make_cons
-                ( c_string_to_lisp_keyword( key ), make_integer( value ) ),
-                meta );
+                   ( c_string_to_lisp_keyword( key ), make_integer( value ) ),
+                   meta );
 }
 
 struct pso_pointer add_meta_string( struct pso_pointer meta, char32_t *key,
                                     char *value ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     value = trim( value );
     char32_t buffer[strlen( value ) + 1];
     mbstowcs( buffer, value, strlen( value ) + 1 );
 
     return
         make_cons( make_cons
-                ( c_string_to_lisp_keyword( key ),
-                  c_string_to_lisp_string( buffer ) ), meta );
+                   ( c_string_to_lisp_keyword( key ),
+                     c_string_to_lisp_string( buffer ) ), meta );
 }
 
 struct pso_pointer add_meta_time( struct pso_pointer meta, char32_t *key,
                                   time_t *value ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     char datestring[256];
 
     strftime( datestring, sizeof( datestring ), nl_langinfo( D_T_FMT ),
diff --git a/src/c/io/io.h b/src/c/io/io.h
index a2b733c..f90e589 100644
--- a/src/c/io/io.h
+++ b/src/c/io/io.h
@@ -21,7 +21,7 @@ extern CURLSH *io_share;
 int initialise_io(  );
 struct pso_pointer initialise_default_streams( struct pso_pointer env );
 
-#define C_IO_IN L"*in*"
+#define C_IO_IN  L"*in*"
 #define C_IO_OUT L"*out*"
 #define C_IO_LOG L"*log*"
 
diff --git a/src/c/io/print.c b/src/c/io/print.c
index fbe2845..d6bf63b 100644
--- a/src/c/io/print.c
+++ b/src/c/io/print.c
@@ -44,9 +44,9 @@
 
 #include "ops/truth.h"
 
-struct pso_pointer in_write(struct pso_pointer p, URL_FILE *output,
-							bool escape);
-							
+struct pso_pointer in_write( struct pso_pointer p, URL_FILE * output,
+                             bool escape );
+
 /**
  * @brief write this character `wc` to this `output` stream, escaping it if
  * 1. `escape` is true; and
@@ -54,75 +54,77 @@ struct pso_pointer in_write(struct pso_pointer p, URL_FILE *output,
  *
  * TODO: this does not yet even nearly cope with all the possible special 
  * cases.
- */							
-void write_char( char32_t wc, URL_FILE * output, bool escape) {
-	if (escape && !iswprint(wc)) {
-		url_fwprintf(output, L"\\%04x", wc);
-		// url_fputwc(L'\\', output);
-	} else {
-		url_fputwc(wc, output);
-	}
+ */
+void write_char( char32_t wc, URL_FILE *output, bool escape ) {
+    if ( escape && !iswprint( wc ) ) {
+        url_fwprintf( output, L"\\%04x", wc );
+        // url_fputwc(L'\\', output);
+    } else {
+        url_fputwc( wc, output );
+    }
 }
 
 
-struct pso_pointer print_string_like_thing(struct pso_pointer p,
-										   URL_FILE *output, bool escape) {
-	switch (get_tag_value(p)) {
-	case KEYTV:
-		url_fputwc(L':', output);
-		break;
-	case STRINGTV:
-		if (escape)
-			url_fputwc(L'"', output);
-		break;
-	}
+struct pso_pointer print_string_like_thing( struct pso_pointer p,
+                                            URL_FILE *output, bool escape ) {
+    switch ( get_tag_value( p ) ) {
+        case KEYTV:
+            url_fputwc( L':', output );
+            break;
+        case STRINGTV:
+            if ( escape )
+                url_fputwc( L'"', output );
+            break;
+    }
 
-	if (keywordp(p) || stringp(p) || symbolp(p)) {
-		for (struct pso_pointer cursor = p; !nilp(cursor);
-			 cursor = pointer_to_object(cursor)->payload.string.cdr) {
-			char32_t wc = pointer_to_object(cursor)->payload.string.character;
+    if ( keywordp( p ) || stringp( p ) || symbolp( p ) ) {
+        for ( struct pso_pointer cursor = p; !nilp( cursor );
+              cursor = pointer_to_object( cursor )->payload.string.cdr ) {
+            char32_t wc =
+                pointer_to_object( cursor )->payload.string.character;
 
-			write_char( wc, output, escape);
-		}
-	}
+            write_char( wc, output, escape );
+        }
+    }
 
-	if (stringp(p)) {
-		if (escape)
-			url_fputwc(L'"', output);
-	}
-	
-	return p;
+    if ( stringp( p ) ) {
+        if ( escape )
+            url_fputwc( L'"', output );
+    }
+
+    return p;
 }
 
-struct pso_pointer write_list_content(struct pso_pointer p, URL_FILE *output,
-									  bool escape) {
-	struct pso_pointer result = nil;
+struct pso_pointer write_list_content( struct pso_pointer p, URL_FILE *output,
+                                       bool escape ) {
+    struct pso_pointer result = nil;
 
-	if (consp(p)) {
-		for (; consp(p); p = c_cdr(p)) {
-			struct pso2 *object = pointer_to_object(p);
+    if ( consp( p ) ) {
+        for ( ; consp( p ); p = c_cdr( p ) ) {
+            struct pso2 *object = pointer_to_object( p );
 
-			result = in_write(object->payload.cons.car, output, escape);
+            result = in_write( object->payload.cons.car, output, escape );
 
-			if (exceptionp(result))
-				break;
+            if ( exceptionp( result ) )
+                break;
 
-			switch (get_tag_value(object->payload.cons.cdr)) {
-			case NILTV:
-				break;
-			case CONSTV:
-				url_fputwc(L' ', output);
-				break;
-			default:
-				url_fputws(L" . ", output);
-				result = in_write(object->payload.cons.cdr, output, escape);
-			}
-		}
-	} else {
-		// TODO: return exception
-	}
+            switch ( get_tag_value( object->payload.cons.cdr ) ) {
+                case NILTV:
+                    break;
+                case CONSTV:
+                    url_fputwc( L' ', output );
+                    break;
+                default:
+                    url_fputws( L" . ", output );
+                    result =
+                        in_write( object->payload.cons.cdr, output, escape );
+            }
+        }
+    } else {
+        // TODO: return exception
+    }
 
-	return result;
+    return result;
 }
 
 /**
@@ -135,52 +137,53 @@ struct pso_pointer write_list_content(struct pso_pointer p, URL_FILE *output,
  *		reader; otherwise, print it appropriately for human readers.
  * @return p on success, exception on failure.
  */
-struct pso_pointer in_write(struct pso_pointer p, URL_FILE *output,
-							bool escape) {
-	struct pso2 *object = pointer_to_object(p);
-	struct pso_pointer result = nil;
+struct pso_pointer in_write( struct pso_pointer p, URL_FILE *output,
+                             bool escape ) {
+    struct pso2 *object = pointer_to_object( p );
+    struct pso_pointer result = nil;
 
-	if (object != NULL) {
-		uint32_t v = get_tag_value(p);
-		switch (v) {
-		case CHARACTERTV:
-			write_char(object->payload.character.character, output, escape);
-			break;
-		case CONSTV:
-			url_fputwc(L'(', output);
-			result = write_list_content(p, output, escape);
-			url_fputwc(L')', output);
-			break;
-		case INTEGERTV:
-			url_fwprintf(output, L"%d",
-						 (int64_t)(object->payload.integer.value));
-			break;
-		case KEYTV:
-		case STRINGTV:
-		case SYMBOLTV:
-			print_string_like_thing(p, output, escape);
-			break;
-		case NILTV:
-			url_fputws(L"nil", output);
-			break;
-		case READTV:
-		case WRITETV:
-			url_fwprintf(output, L"<%s stream: ",
-						 v == READTV ? "read" : "write");
-			in_write(object->payload.stream.meta, output, escape);
-			url_fputwc(L'>', output);
-			break;
-		case TRUETV:
-			url_fputwc(L't', output);
-			break;
-		default:
-			// TODO: return exception
-		}
-	} else {
-		// TODO: return exception
-	}
+    if ( object != NULL ) {
+        uint32_t v = get_tag_value( p );
+        switch ( v ) {
+            case CHARACTERTV:
+                write_char( object->payload.character.character, output,
+                            escape );
+                break;
+            case CONSTV:
+                url_fputwc( L'(', output );
+                result = write_list_content( p, output, escape );
+                url_fputwc( L')', output );
+                break;
+            case INTEGERTV:
+                url_fwprintf( output, L"%d",
+                              ( int64_t ) ( object->payload.integer.value ) );
+                break;
+            case KEYTV:
+            case STRINGTV:
+            case SYMBOLTV:
+                print_string_like_thing( p, output, escape );
+                break;
+            case NILTV:
+                url_fputws( L"nil", output );
+                break;
+            case READTV:
+            case WRITETV:
+                url_fwprintf( output, L"<%s stream: ",
+                              v == READTV ? "read" : "write" );
+                in_write( object->payload.stream.meta, output, escape );
+                url_fputwc( L'>', output );
+                break;
+            case TRUETV:
+                url_fputwc( L't', output );
+                break;
+            default:
+                // TODO: return exception
+        }
+    } else {
+        // TODO: return exception
+    }
 
-	return result;
+    return result;
 }
 
 /**
@@ -195,31 +198,32 @@ struct pso_pointer in_write(struct pso_pointer p, URL_FILE *output,
  * @param nl_after if true, print a newline *after* printing `p`; else a space.
  * @return p on success, exception on failure.
  */
-struct pso_pointer write(struct pso_pointer p, struct pso_pointer stream,
-						 bool escape, bool nl_before, bool nl_after) {
-	struct pso_pointer result = p;
-	URL_FILE *output = writep(stream)
-						   ? pointer_to_object(stream)->payload.stream.stream
-						   : file_to_url_file(stdout);
+struct pso_pointer write( struct pso_pointer p, struct pso_pointer stream,
+                          bool escape, bool nl_before, bool nl_after ) {
+    struct pso_pointer result = p;
+    URL_FILE *output = writep( stream )
+        ? pointer_to_object( stream )->payload.stream.stream
+        : file_to_url_file( stdout );
 
-	if (writep(stream)) {
-		inc_ref(stream);
+    if ( writep( stream ) ) {
+        inc_ref( stream );
 
-		if (nl_before)
-			url_fputwc(L'\n', output);
+        if ( nl_before )
+            url_fputwc( L'\n', output );
 
-		result = in_write(p, output, true);
+        result = in_write( p, output, true );
 
-		url_fputwc(nl_after ? L'\n' : L' ', output);
+        url_fputwc( nl_after ? L'\n' : L' ', output );
 
-		dec_ref(stream);
-	} else {
-		result = make_exception(
-			c_string_to_lisp_string(L"Bad write stream passed to write."), nil,
-			nil, nil);
-	}
+        dec_ref( stream );
+    } else {
+        result =
+            make_exception( c_string_to_lisp_string
+                            ( L"Bad write stream passed to write." ), nil, nil,
+                            nil );
+    }
 
-	return result;
+    return result;
 }
 
 /**
@@ -229,13 +233,13 @@ struct pso_pointer write(struct pso_pointer p, struct pso_pointer stream,
  * @param stream if a pointer to an open write stream, print to there.
  * @return struct pso_pointer `nil`, or an exception if some erroe occurred.
  */
-struct pso_pointer c_print(struct pso_pointer p, struct pso_pointer stream) {
-	return write(p, stream, true, true, false);
+struct pso_pointer c_print( struct pso_pointer p, struct pso_pointer stream ) {
+    return write( p, stream, true, true, false );
 }
 
 /**
  * @brief princ is pretty much like print except things are printed `unescaped`
  */
-struct pso_pointer c_princ(struct pso_pointer p, struct pso_pointer stream) {
-	return write(p, stream, false, true, false);
+struct pso_pointer c_princ( struct pso_pointer p, struct pso_pointer stream ) {
+    return write( p, stream, false, true, false );
 }
diff --git a/src/c/memory/memory.c b/src/c/memory/memory.c
index b4b84cd..6e7e5af 100644
--- a/src/c/memory/memory.c
+++ b/src/c/memory/memory.c
@@ -77,60 +77,60 @@ struct pso_pointer initialise_memory( uint32_t node ) {
 /**
  * @brief Pop an object off the freelist for the specified `size_class`.
  */
-struct pso_pointer pop_freelist( uint8_t size_class) {
-	// `t`, because if `allocate_page` fails it will be set to `nil`.
-	struct pso_pointer result = t;
-		
-	if ( size_class <= MAX_SIZE_CLASS ) {
-	    if ( nilp( freelists[size_class] ) ) {
-	        result = allocate_page( size_class );
-	    }
+struct pso_pointer pop_freelist( uint8_t size_class ) {
+    // `t`, because if `allocate_page` fails it will be set to `nil`.
+    struct pso_pointer result = t;
 
-	    if ( nilp( result ) ) {
-	        fputws( L"FATAL: Page space exhausted\n", stderr );
-	        exit( 1 );          // TODO: we don't want to do this! Somehow, we need to
-	        // recover a workable environment, ideally by throwing a pre-made
-	        // exception.
-	    }
+    if ( size_class <= MAX_SIZE_CLASS ) {
+        if ( nilp( freelists[size_class] ) ) {
+            result = allocate_page( size_class );
+        }
 
-	    if ( !exceptionp( result ) && !nilp( result ) ) {
-			pthread_mutex_lock( &freelists_mutices[size_class]);
-	        result = freelists[size_class];
-	        struct pso2 *object = pointer_to_object( result );
-	        freelists[size_class] = object->payload.free.next;
-			pthread_mutex_unlock(&freelists_mutices[size_class]);
+        if ( nilp( result ) ) {
+            fputws( L"FATAL: Page space exhausted\n", stderr );
+            exit( 1 );          // TODO: we don't want to do this! Somehow, we need to
+            // recover a workable environment, ideally by throwing a pre-made
+            // exception.
+        }
 
-	        /* the object ought already to have the right size class in its tag
-	         * because it was popped off the freelist for that size class. */
-	        if ( object->header.tag.bytes.size_class != size_class ) {
-	            // TODO: return an exception instead? Or warn, set it, and continue?
-	        }
-	        /* the objext ought to have a reference count ot zero, because it's 
-	         * on the freelist, but again we should sanity check. */
-	        if ( object->header.count != 0 ) {
-	            fwprintf( stderr, 
-					L"WARNING: Request to allocate object of size class %d, which is not implemented", 
-					size_class);
-	        }
-	    }
-	}                           // TODO: else throw exception
-	
-	return result;
+        if ( !exceptionp( result ) && !nilp( result ) ) {
+            pthread_mutex_lock( &freelists_mutices[size_class] );
+            result = freelists[size_class];
+            struct pso2 *object = pointer_to_object( result );
+            freelists[size_class] = object->payload.free.next;
+            pthread_mutex_unlock( &freelists_mutices[size_class] );
+
+            /* the object ought already to have the right size class in its tag
+             * because it was popped off the freelist for that size class. */
+            if ( object->header.tag.bytes.size_class != size_class ) {
+                // TODO: return an exception instead? Or warn, set it, and continue?
+            }
+            /* the objext ought to have a reference count ot zero, because it's 
+             * on the freelist, but again we should sanity check. */
+            if ( object->header.count != 0 ) {
+                fwprintf( stderr,
+                          L"WARNING: Request to allocate object of size class %d, which is not implemented",
+                          size_class );
+            }
+        }
+    }                           // TODO: else throw exception
+
+    return result;
 }
 
-void push_freelist( struct pso_pointer p) {
-	struct pso2 *obj = pointer_to_object( p );
-	uint8_t size_class = ( obj->header.tag.bytes.size_class );
+void push_freelist( struct pso_pointer p ) {
+    struct pso2 *obj = pointer_to_object( p );
+    uint8_t size_class = ( obj->header.tag.bytes.size_class );
 
-	strncpy( ( char * ) ( obj->header.tag.bytes.mnemonic ), FREETAG,
-	         TAGLENGTH );
-	
-	pthread_mutex_lock( &freelists_mutices[size_class]);
+    strncpy( ( char * ) ( obj->header.tag.bytes.mnemonic ), FREETAG,
+             TAGLENGTH );
 
-	if ( size_class <= MAX_SIZE_CLASS ) {
-		obj->payload.free.next = freelists[size_class];
-		freelists[size_class] = p;
-	}
-	
-	pthread_mutex_unlock(&freelists_mutices[size_class]);
+    pthread_mutex_lock( &freelists_mutices[size_class] );
+
+    if ( size_class <= MAX_SIZE_CLASS ) {
+        obj->payload.free.next = freelists[size_class];
+        freelists[size_class] = p;
+    }
+
+    pthread_mutex_unlock( &freelists_mutices[size_class] );
 }
diff --git a/src/c/memory/memory.h b/src/c/memory/memory.h
index 720bf1d..776e140 100644
--- a/src/c/memory/memory.h
+++ b/src/c/memory/memory.h
@@ -10,6 +10,7 @@
 #ifndef __psse_memory_memory_h
 #define __psse_memory_memory_h
 #include <pthread.h>
+#include <stdbool.h>
 
 #include "memory/pointer.h"
 
@@ -26,10 +27,11 @@
 
 struct pso_pointer initialise_memory(  );
 
-struct pso_pointer pop_freelist( uint8_t size_class);
-void push_freelist( struct pso_pointer p);
+struct pso_pointer pop_freelist( uint8_t size_class );
+void push_freelist( struct pso_pointer p );
 
 extern struct pso_pointer out_of_memory_exception;
 extern struct pso_pointer freelists[];
 extern pthread_mutex_t freelists_mutices[];
+extern bool memory_initialised;
 #endif
diff --git a/src/c/memory/page.c b/src/c/memory/page.c
index 2cc12c7..9857a1d 100644
--- a/src/c/memory/page.c
+++ b/src/c/memory/page.c
@@ -319,11 +319,11 @@ struct pso_pointer allocate_page( uint8_t size_class ) {
                               L"\nAllocated page %d for objects of size class %x.\n",
                               npages_allocated, size_class );
 
-				pthread_mutex_lock( &freelists_mutices[size_class]);
+                pthread_mutex_lock( &freelists_mutices[size_class] );
                 freelists[size_class] =
                     initialise_page( ( union page * ) pg, npages_allocated,
                                      size_class, freelists[size_class] );
-				pthread_mutex_unlock( &freelists_mutices[size_class]);
+                pthread_mutex_unlock( &freelists_mutices[size_class] );
 
                 debug_printf( DEBUG_ALLOC, 0,
                               L"Initialised page %d; freelist for size class %x updated with head at page %d, offset %d.\n",
diff --git a/src/c/memory/pso.c b/src/c/memory/pso.c
index 1a25c26..f6a241c 100644
--- a/src/c/memory/pso.c
+++ b/src/c/memory/pso.c
@@ -35,16 +35,20 @@
 #include "ops/truth.h"
 
  /**
-  * @brief Allocate an object of this size_class with this tag.
+  * @brief Allocate an object of this `size_class` with this `tag`.
   *
   * All objects that are allocated (after completion of init)) should be linked
-  * onto the `locals` slot on a stack frame. This guarantees
-  * 1. that they get `inc_ref`ed; and that, 
+  * onto the `locals` slot of a stack frame. This guarantees
+  * 1. that they do get `inc_ref`ed; and that, 
   * 2. if nothing else hangs onto them they will be reclaimed when that stack
   *    frame is reclaimed.
   * for some objects (e.g. those cons cells on the locals list) this isn't 
   * possible due to infinite recursion, but those special cases need to be
-  * audited carefully
+  * audited carefully.
+  *
+  * The stack frame pointer is DELIBERATELY a C pointer, not a Lisp pointer,
+  * because you are definitely not supposed to be calling this function from
+  * Lisp. Please do not!
   * 
   * @param stack_pointer C (NOT Lisp!) pointer to an active stack frame (or
   *	NULL, but only during initialisation).
@@ -52,8 +56,9 @@
   * @param size_class The size class for the object to be allocated;
   * @return struct pso_pointer a pointer to the newly allocated object
   */
-struct pso_pointer allocate( /* struct pso4 * stack_pointer,*/ char *tag, uint8_t size_class ) {
-	// todo: issue #21: must have stack frame passed in.
+struct pso_pointer allocate( struct pso4 *stack_pointer, char *tag,
+                             uint8_t size_class ) {
+    // todo: issue #21: must have stack frame passed in.
 
 #ifdef DEBUG
     debug_printf( DEBUG_ALLOC, 0,
@@ -61,26 +66,29 @@ struct pso_pointer allocate( /* struct pso4 * stack_pointer,*/ char *tag, uint8_
                   size_class, tag );
 #endif
 
-	struct pso_pointer result = pop_freelist(size_class); 
+    struct pso_pointer result = pop_freelist( size_class );
 
-	if (!nilp( result)) {
-		strncpy( ( char * ) ( pointer_to_object(result)->header.tag.bytes.mnemonic ), tag,
-		         TAGLENGTH );
-	
-		debug_printf( DEBUG_ALLOC, 0, L"at page %d, offset %d... ",
-		              result.page, result.offset );
-//			if ( stack_pointer != NULL && 
-//				(stack_pointer->header.tag.value & 0xffffff) == STACKTV) {
-//				struct pso_pointer locals = make_cons(result,
-//					 stack_pointer->payload.stack_frame.locals);
-//				stack_pointer->payload.stack_frame.locals = locals;
-//				
-//			} else {
-//				fputws( L"WARNING: No stack frame passed to `allocate`.\n", stderr);
-//			}
-		} else {
-	//		TODO: throw exception
-		}
+    if ( !nilp( result ) ) {
+        strncpy( ( char * ) ( pointer_to_object( result )->header.tag.bytes.
+                              mnemonic ), tag, TAGLENGTH );
+
+        debug_printf( DEBUG_ALLOC, 0, L"at page %d, offset %d... ",
+                      result.page, result.offset );
+        if ( stack_pointer != NULL &&
+             ( stack_pointer->header.tag.value & 0xffffff ) == STACKTV ) {
+            struct pso_pointer locals = make_cons( result,
+                                                   stack_pointer->
+                                                   payload.stack_frame.
+                                                   locals );
+            stack_pointer->payload.stack_frame.locals = locals;
+
+        } else if ( memory_initialised ) {
+            fputws( L"WARNING: No stack frame passed to `allocate`.\n",
+                    stderr );
+        }
+    } else {
+        //    TODO: throw exception
+    }
 
 #ifdef DEBUG
     debug_print( exceptionp( result ) ? L"fail\n" : L"success\n", DEBUG_ALLOC,
@@ -203,7 +211,7 @@ struct pso_pointer free_object( struct pso_pointer p ) {
         obj->payload.words[i] = 0;
     }
 
-	push_freelist(p);
+    push_freelist( p );
 
     return result;
 }
diff --git a/src/c/memory/pso.h b/src/c/memory/pso.h
index c9894cf..38a18f6 100644
--- a/src/c/memory/pso.h
+++ b/src/c/memory/pso.h
@@ -14,9 +14,10 @@
 
 #include "memory/header.h"
 #include "memory/pointer.h"
+#include "memory/pso4.h"
 
-// todo: issue #21: must have stack frame passed in.
-struct pso_pointer allocate( char *tag, uint8_t size_class );
+struct pso_pointer allocate( struct pso4 *stack_pointer, char *tag,
+                             uint8_t size_class );
 
 struct pso_pointer dec_ref( struct pso_pointer pointer );
 
diff --git a/src/c/ops/bind.c b/src/c/ops/bind.c
index e34122c..32e1f4e 100644
--- a/src/c/ops/bind.c
+++ b/src/c/ops/bind.c
@@ -41,6 +41,6 @@ struct pso_pointer lisp_bind(
 struct pso_pointer c_bind( struct pso_pointer key,
                            struct pso_pointer value,
                            struct pso_pointer store ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     return make_cons( make_cons( key, value ), store );
 }
diff --git a/src/c/ops/eval_apply.c b/src/c/ops/eval_apply.c
index 819a2eb..7d39ca2 100644
--- a/src/c/ops/eval_apply.c
+++ b/src/c/ops/eval_apply.c
@@ -85,12 +85,18 @@ struct pso_pointer eval(
         default:
             result =
                 make_exception( make_cons
-                                ( c_string_to_lisp_string
-                                  ( L"Can't yet evaluate things of this type: " ),
-                                  result ), frame_pointer,
-                                make_cons( make_cons
-                                        ( c_string_to_lisp_keyword( L"tag" ),
-                                          get_tag_string( result ) ), nil ),
+                                ( frame, c_string_to_lisp_string
+                                  ( frame,
+                                    L"Can't yet evaluate things of this type: " ),
+                                  result ), frame_pointer, make_cons( frame,
+                                                                      make_cons
+                                                                      ( frame,
+                                                                        c_string_to_lisp_keyword
+                                                                        ( frame,
+                                                                          L"tag" ),
+                                                                        get_tag_string
+                                                                        ( result ) ),
+                                                                      nil ),
                                 nil );
     }
 
diff --git a/src/c/ops/list_ops.c b/src/c/ops/list_ops.c
index 4e58600..8036c47 100644
--- a/src/c/ops/list_ops.c
+++ b/src/c/ops/list_ops.c
@@ -44,7 +44,7 @@ struct pso_pointer cdr(
 #ifdef MANAGED_POINTER_ONLY
     struct pso4 *frame = pointer_to_pso4( frame_pointer );
 #endif
-    return c_cdr( fetch_arg( frame, 0 ) );
+    return c_cdr( frame, fetch_arg( frame, 0 ) );
 }
 
 /**
@@ -66,7 +66,7 @@ struct pso_pointer cons(
     struct pso4 *frame = pointer_to_pso4( frame_pointer );
 
 #endif
-    return make_cons( fetch_arg( frame, 0 ), fetch_arg( frame, 1 ) );
+    return make_cons( frame, fetch_arg( frame, 0 ), fetch_arg( frame, 1 ) );
 }
 
 #endif
diff --git a/src/c/ops/repl.c b/src/c/ops/repl.c
index c3fa5a1..f470477 100644
--- a/src/c/ops/repl.c
+++ b/src/c/ops/repl.c
@@ -48,11 +48,13 @@ void int_handler( int dummy ) {
  * Very simple read/eval/print loop for bootstrapping.
  */
 void c_repl( bool show_prompt ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     signal( SIGINT, int_handler );
     debug_print( L"Entered repl\n", DEBUG_REPL, 0 );
 
-    struct pso_pointer env = consp( oblist ) ? oblist : make_cons( oblist, nil );
+    // TODO: NULL is not OK here, but will do until we have a REPL in Lisp.
+    struct pso_pointer env =
+        consp( oblist ) ? oblist : make_cons( NULL, oblist, nil );
     struct pso_pointer input_stream = c_assoc( lisp_io_in, env );
     struct pso_pointer output_stream = c_assoc( lisp_io_out, env );
 
diff --git a/src/c/ops/repl.h b/src/c/ops/repl.h
index aa8c416..0dc862f 100644
--- a/src/c/ops/repl.h
+++ b/src/c/ops/repl.h
@@ -13,7 +13,7 @@
 #define SRC_C_OPS_REPL_H_
 
 
-	// todo: issue #21: must have stack frame passed in.
+  // todo: issue #21: must have stack frame passed in.
 void c_repl(  );
 
 
diff --git a/src/c/ops/reverse.c b/src/c/ops/reverse.c
index 4e2704b..7bf3bc2 100644
--- a/src/c/ops/reverse.c
+++ b/src/c/ops/reverse.c
@@ -36,7 +36,7 @@
  * 		the argument was not a sequence.
  */
 struct pso_pointer c_reverse( struct pso_pointer sequence ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     struct pso_pointer result = nil;
 
     for ( struct pso_pointer cursor = sequence; !nilp( sequence );
@@ -66,8 +66,8 @@ struct pso_pointer c_reverse( struct pso_pointer sequence ) {
             default:
                 result =
                     make_exception( make_cons( c_string_to_lisp_string
-                                            ( L"Invalid object in sequence" ),
-                                            cursor ), nil, nil, nil );
+                                               ( L"Invalid object in sequence" ),
+                                               cursor ), nil, nil, nil );
                 goto exit;
                 break;
         }
diff --git a/src/c/ops/string_ops.c b/src/c/ops/string_ops.c
index f84d327..bc199d1 100644
--- a/src/c/ops/string_ops.c
+++ b/src/c/ops/string_ops.c
@@ -69,12 +69,13 @@ uint32_t calculate_hash( wint_t c, struct pso_pointer ptr ) {
  * char32_t in larger pso classes, so this function may be only for strings
  * (and thus simpler).
  */
-struct pso_pointer make_string_like_thing( wint_t c, struct pso_pointer tail,
+struct pso_pointer make_string_like_thing( struct pso4 *frame_pointer,
+                                           wint_t c, struct pso_pointer tail,
                                            char *tag ) {
     struct pso_pointer pointer = tail;
 
     if ( check_type( tail, tag ) || nilp( tail ) ) {
-        pointer = allocate( tag, CONS_SIZE_CLASS );
+        pointer = allocate( frame_pointer, tag, CONS_SIZE_CLASS );
         struct pso2 *cell = pointer_to_object( pointer );
 
         cell->payload.string.character = c;
@@ -106,8 +107,9 @@ struct pso_pointer make_string_like_thing( wint_t c, struct pso_pointer tail,
  * @param c the character to add (prepend);
  * @param tail the string which is being built.
  */
-struct pso_pointer make_string( wint_t c, struct pso_pointer tail ) {
-    return make_string_like_thing( c, tail, STRINGTAG );
+struct pso_pointer make_string( struct pso4 *frame_pointer, wint_t c,
+                                struct pso_pointer tail ) {
+    return make_string_like_thing( frame_pointer, c, tail, STRINGTAG );
 }
 
 /**
@@ -118,8 +120,9 @@ struct pso_pointer make_string( wint_t c, struct pso_pointer tail ) {
  * @param c the character to add (prepend);
  * @param tail the keyword which is being built.
  */
-struct pso_pointer make_keyword( wint_t c, struct pso_pointer tail ) {
-    return make_string_like_thing( c, tail, KEYTAG );
+struct pso_pointer make_keyword( struct pso4 *frame_pointer, wint_t c,
+                                 struct pso_pointer tail ) {
+    return make_string_like_thing( frame_pointer, c, tail, KEYTAG );
 }
 
 /**
@@ -130,22 +133,26 @@ struct pso_pointer make_keyword( wint_t c, struct pso_pointer tail ) {
  * @param c the character to add (prepend);
  * @param tail the symbol which is being built.
  */
-struct pso_pointer make_symbol( wint_t c, struct pso_pointer tail ) {
-    return make_string_like_thing( c, tail, SYMBOLTAG );
+struct pso_pointer make_symbol( struct pso4 *frame_pointer, wint_t c,
+                                struct pso_pointer tail ) {
+    return make_string_like_thing( frame_pointer, c, tail, SYMBOLTAG );
 }
 
 
 /**
  * Return a lisp string representation of this wide character string.
  */
-struct pso_pointer c_string_to_lisp_string( char32_t *string ) {
+struct pso_pointer c_string_to_lisp_string( struct pso4 *frame_pointer,
+                                            char32_t *string ) {
     struct pso_pointer result = nil;
 
     for ( int i = wcslen( string ) - 1; i >= 0; i-- ) {
         if ( string[i] != '"' ) {
-            result = make_string( string[i], result );
+            result = make_string( frame_pointer, string[i], result );
         } else {
-            result = make_string( L'\\', make_string( string[i], result ) );
+            result = make_string( frame_pointer, L'\\',
+                                  make_string( frame_pointer, string[i],
+                                               result ) );
         }
     }
 
@@ -157,14 +164,15 @@ struct pso_pointer c_string_to_lisp_string( char32_t *string ) {
  * Return a lisp symbol representation of this wide character string. In
  * symbols, I am accepting only lower case characters.
  */
-struct pso_pointer c_string_to_lisp_symbol( char32_t *symbol ) {
+struct pso_pointer c_string_to_lisp_symbol( struct pso4 *frame_pointer,
+                                            char32_t *symbol ) {
     struct pso_pointer result = nil;
 
     for ( int i = wcslen( symbol ) - 1; i >= 0; i-- ) {
         char32_t c = towlower( symbol[i] );
 
         if ( iswalpha( c ) || c == L'-' || c == L'*' ) {
-            result = make_symbol( c, result );
+            result = make_symbol( frame_pointer, c, result );
         }
     }
 
@@ -175,14 +183,15 @@ struct pso_pointer c_string_to_lisp_symbol( char32_t *symbol ) {
  * Return a lisp keyword representation of this wide character string. In
  * keywords, I am accepting only lower case characters and numbers.
  */
-struct pso_pointer c_string_to_lisp_keyword( char32_t *symbol ) {
+struct pso_pointer c_string_to_lisp_keyword( struct pso4 *frame_pointer,
+                                             char32_t *symbol ) {
     struct pso_pointer result = nil;
 
     for ( int i = wcslen( symbol ) - 1; i >= 0; i-- ) {
         char32_t c = towlower( symbol[i] );
 
         if ( iswalnum( c ) || c == L'-' ) {
-            result = make_keyword( c, result );
+            result = make_keyword( frame_pointer, c, result );
         }
     }
 
diff --git a/src/c/ops/string_ops.h b/src/c/ops/string_ops.h
index d17d9fc..aeaf243 100644
--- a/src/c/ops/string_ops.h
+++ b/src/c/ops/string_ops.h
@@ -17,19 +17,26 @@
 #include <wchar.h>
 #include <wctype.h>
 
-struct pso_pointer make_string_like_thing( wint_t c, struct pso_pointer tail,
+struct pso_pointer make_string_like_thing( struct pso4 *frame_pointer,
+                                           wint_t c, struct pso_pointer tail,
                                            char *tag );
 
-struct pso_pointer make_string( wint_t c, struct pso_pointer tail );
+struct pso_pointer make_string( struct pso4 *frame_pointer, wint_t c,
+                                struct pso_pointer tail );
 
-struct pso_pointer make_keyword( wint_t c, struct pso_pointer tail );
+struct pso_pointer make_keyword( struct pso4 *frame_pointer, wint_t c,
+                                 struct pso_pointer tail );
 
-struct pso_pointer make_symbol( wint_t c, struct pso_pointer tail );
+struct pso_pointer make_symbol( struct pso4 *frame_pointer, wint_t c,
+                                struct pso_pointer tail );
 
-struct pso_pointer c_string_to_lisp_string( char32_t *string );
+struct pso_pointer c_string_to_lisp_string( struct pso4 *frame_pointer,
+                                            char32_t * string );
 
-struct pso_pointer c_string_to_lisp_keyword( char32_t *symbol );
+struct pso_pointer c_string_to_lisp_keyword( struct pso4 *frame_pointer,
+                                             char32_t * symbol );
 
-struct pso_pointer c_string_to_lisp_symbol( char32_t *symbol );
+struct pso_pointer c_string_to_lisp_symbol( struct pso4 *frame_pointer,
+                                            char32_t * symbol );
 
 #endif
diff --git a/src/c/payloads/character.c b/src/c/payloads/character.c
index cb807c1..962724c 100644
--- a/src/c/payloads/character.c
+++ b/src/c/payloads/character.c
@@ -24,8 +24,8 @@
 
 #include "payloads/character.h"
 
-struct pso_pointer make_character( wint_t c ) {
-    struct pso_pointer result = allocate( CHARACTERTAG, 2 );
+struct pso_pointer make_character( struct pso4 *frame_pointer, wint_t c ) {
+    struct pso_pointer result = allocate( frame_pointer, CHARACTERTAG, 2 );
 
     if ( !nilp( result ) ) {
         pointer_to_object( result )->payload.character.character =
diff --git a/src/c/payloads/character.h b/src/c/payloads/character.h
index 1f5e099..a901642 100644
--- a/src/c/payloads/character.h
+++ b/src/c/payloads/character.h
@@ -26,6 +26,7 @@
 #include <wchar.h>
 #include <wctype.h>
 
+#include "memory/pso4.h"
 
 #define CHARTAG "CHR"
 #define CHARTV  5392451
@@ -37,5 +38,5 @@ struct character_payload {
     char32_t character;
 };
 
-struct pso_pointer make_character( wint_t c );
+struct pso_pointer make_character( struct pso4 *frame_pointer, wint_t c );
 #endif
diff --git a/src/c/payloads/cons.c b/src/c/payloads/cons.c
index 8a05088..9af48b7 100644
--- a/src/c/payloads/cons.c
+++ b/src/c/payloads/cons.c
@@ -30,9 +30,11 @@
  * @param cdr the pointer which should form the cdr of this cons cell.
  * @return struct pso_pointer a pointer to the newly allocated cons cell.
  */
-struct pso_pointer make_cons(struct pso_pointer car, struct pso_pointer cdr) {
-	// todo: issue #21: must have stack frame passed in.
-    struct pso_pointer result = allocate( CONSTAG, 2 );
+struct pso_pointer make_cons( struct pso4 *frame_pointer,
+                              struct pso_pointer car,
+                              struct pso_pointer cdr ) {
+    // todo: issue #21: must have stack frame passed in.
+    struct pso_pointer result = allocate( frame_pointer, CONSTAG, 2 );
 
     struct pso2 *object = pointer_to_object( result );
     object->payload.cons.car = inc_ref( car );
@@ -68,8 +70,8 @@ struct pso_pointer c_car( struct pso_pointer cons ) {
  * @return the cdr of the indicated cell.
  * @exception if the pointer does not indicate a cons cell.
  */
-struct pso_pointer c_cdr(struct pso_pointer p) {
-	// todo: issue #21: must have stack frame passed in.
+struct pso_pointer c_cdr( struct pso4 *stack_pointer, struct pso_pointer p ) {
+    // todo: issue #21: must have stack frame passed in.
     struct pso_pointer result = nil;
     struct pso2 *object = pointer_to_object( p );
 
@@ -85,8 +87,8 @@ struct pso_pointer c_cdr(struct pso_pointer p) {
         default:
             result =
                 make_exception( make_cons
-                                ( c_string_to_lisp_string
-                                  ( L"Invalid type for cdr" ),
+                                ( stack_pointer, c_string_to_lisp_string
+                                  ( stack_pointer, L"Invalid type for cdr" ),
                                   get_tag_string( p ) ), nil, nil, nil );
             break;
     }
@@ -109,6 +111,6 @@ struct pso_pointer destroy_cons( struct pso_pointer fp,
         struct pso4 *frame = pointer_to_pso4( fp );
         struct pso_pointer p = frame->payload.stack_frame.arg[0];
         dec_ref( c_car( p ) );
-        dec_ref( c_cdr( p ) );
+        dec_ref( c_cdr( frame, p ) );
     }
 }
diff --git a/src/c/payloads/cons.h b/src/c/payloads/cons.h
index 0192f4e..21b2334 100644
--- a/src/c/payloads/cons.h
+++ b/src/c/payloads/cons.h
@@ -12,6 +12,7 @@
 #include <stdbool.h>
 
 #include "memory/pointer.h"
+#include "memory/pso4.h"
 
 #define CONS_SIZE_CLASS 2
 
@@ -28,10 +29,12 @@ struct cons_payload {
 
 struct pso_pointer c_car( struct pso_pointer cons );
 
-struct pso_pointer c_cdr( struct pso_pointer cons );
+struct pso_pointer c_cdr( struct pso4 *stack_pointer,
+                          struct pso_pointer cons );
 
 // todo: issue #21: must have stack frame passed in.
-struct pso_pointer make_cons( struct pso_pointer car, struct pso_pointer cdr );
+struct pso_pointer make_cons( struct pso4 *stack_pointer,
+                              struct pso_pointer car, struct pso_pointer cdr );
 
 struct pso_pointer destroy_cons( struct pso_pointer fp,
                                  struct pso_pointer env );
diff --git a/src/c/payloads/exception.c b/src/c/payloads/exception.c
index 8817894..28da143 100644
--- a/src/c/payloads/exception.c
+++ b/src/c/payloads/exception.c
@@ -38,7 +38,8 @@ struct pso_pointer make_exception( struct pso_pointer message,
                                    struct pso_pointer frame,
                                    struct pso_pointer meta,
                                    struct pso_pointer cause ) {
-    struct pso_pointer result = allocate( EXCEPTIONTAG, 3 );
+    struct pso_pointer result =
+        allocate( pointer_to_pso4( frame ), EXCEPTIONTAG, 3 );
 
     if ( !nilp( result ) && !exceptionp( result ) ) {
         struct pso3 *object = ( struct pso3 * ) pointer_to_object( result );
diff --git a/src/c/payloads/integer.c b/src/c/payloads/integer.c
index 8437a8b..0c0e861 100644
--- a/src/c/payloads/integer.c
+++ b/src/c/payloads/integer.c
@@ -14,6 +14,7 @@
 #include "memory/pointer.h"
 #include "memory/pso.h"
 #include "memory/pso2.h"
+#include "memory/pso4.h"
 #include "memory/tags.h"
 
 #include "debug.h"
@@ -24,11 +25,11 @@
  * @param more `nil`, or a pointer to the more significant cell(s) of this number.
  * *NOTE* that if `more` is not `nil`, `value` *must not* exceed `MAX_INTEGER`.
  */
-struct pso_pointer make_integer( int64_t value ) {
+struct pso_pointer make_integer( struct pso4 *frame_pointer, int64_t value ) {
     struct pso_pointer result = nil;
     debug_print( L"Entering make_integer\n", DEBUG_ALLOC, 0 );
 
-    result = allocate( INTEGERTAG, 2 );
+    result = allocate( frame_pointer, INTEGERTAG, 2 );
     struct pso2 *cell = pointer_to_object( result );
     cell->payload.integer.value = value;
 
diff --git a/src/c/payloads/integer.h b/src/c/payloads/integer.h
index 0a391aa..9205ebc 100644
--- a/src/c/payloads/integer.h
+++ b/src/c/payloads/integer.h
@@ -12,6 +12,8 @@
 
 #include <stdint.h>
 
+#include "memory/pso4.h"
+
 /**
  * @brief An integer .
  *
@@ -23,6 +25,6 @@ struct integer_payload {
     __int128_t value;
 };
 
-struct pso_pointer make_integer( int64_t value );
+struct pso_pointer make_integer( struct pso4 *frame_pointer, int64_t value );
 
 #endif
diff --git a/src/c/payloads/psse_string.c b/src/c/payloads/psse_string.c
index 8a4bdbe..ad23d19 100644
--- a/src/c/payloads/psse_string.c
+++ b/src/c/payloads/psse_string.c
@@ -8,23 +8,19 @@
  */
 
 
-#include <stdint.h>
 
  /*
   * wide characters
   */
-#include <wchar.h>
-#include <wctype.h>
 
 #include "memory/node.h"
 #include "memory/pointer.h"
 #include "memory/pso.h"
-#include "memory/pso2.h"
 #include "memory/pso4.h"
 #include "memory/tags.h"
 
-#include "ops/string_ops.h"
-#include "ops/truth.h"
+#include "payloads/cons.h"
+
 
 /**
  * @brief When an string is freed, its cdr pointer must be decremented.
@@ -38,7 +34,7 @@ struct pso_pointer destroy_string( struct pso_pointer fp,
         struct pso4 *frame = pointer_to_pso4( fp );
         struct pso_pointer p = frame->payload.stack_frame.arg[0];
 
-        dec_ref( c_cdr( p ) );
+        dec_ref( c_cdr( frame, p ) );
     }
 
     return nil;
diff --git a/src/c/payloads/read_stream.c b/src/c/payloads/read_stream.c
index a0b0876..1286335 100644
--- a/src/c/payloads/read_stream.c
+++ b/src/c/payloads/read_stream.c
@@ -15,6 +15,7 @@
 #include "memory/pointer.h"
 #include "memory/pso.h"
 #include "memory/pso2.h"
+#include "memory/pso4.h"
 #include "memory/tags.h"
 
 
@@ -24,9 +25,10 @@
  * @param metadata a pointer to an associaton containing metadata on the stream.
  * @return a pointer to the new read stream.
  */
-struct pso_pointer make_read_stream( URL_FILE *input,
+struct pso_pointer make_read_stream( struct pso4 *frame_pointer,
+                                     URL_FILE *input,
                                      struct pso_pointer metadata ) {
-    struct pso_pointer pointer = allocate( READTAG, 2 );
+    struct pso_pointer pointer = allocate( frame_pointer, READTAG, 2 );
     struct pso2 *cell = pointer_to_object( pointer );
 
     cell->payload.stream.stream = input;
diff --git a/src/c/payloads/read_stream.h b/src/c/payloads/read_stream.h
index 1ea0adb..23a04a7 100644
--- a/src/c/payloads/read_stream.h
+++ b/src/c/payloads/read_stream.h
@@ -29,7 +29,8 @@ struct stream_payload {
     struct pso_pointer meta;
 };
 
-struct pso_pointer make_read_stream( URL_FILE * input,
+struct pso_pointer make_read_stream( struct pso4 *frame_pointer,
+                                     URL_FILE * input,
                                      struct pso_pointer metadata );
 
 #endif
diff --git a/src/c/payloads/stack.c b/src/c/payloads/stack.c
index 89fb617..0b025ca 100644
--- a/src/c/payloads/stack.c
+++ b/src/c/payloads/stack.c
@@ -33,12 +33,13 @@
  */
 struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
                                ... ) {
-	// todo: issue #21: must have stack frame passed in.
+    // todo: issue #21: must have stack frame passed in.
     va_list args;
     va_start( args, previous );
 
-    struct pso_pointer frame_pointer = allocate( STACKTAG, 4 );
-    struct pso4 *frame = ( struct pso4 * ) pointer_to_object( frame_pointer );
+    struct pso4 *frame = pointer_to_pso4( previous );
+    struct pso_pointer frame_pointer =
+        allocate( pointer_to_pso4( previous ), STACKTAG, 4 );
 
 #ifdef DEBUG
     debug_printf( DEBUG_ALLOC, 0,
@@ -72,7 +73,8 @@ struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
 
         for ( ; cursor < arg_count; cursor++ ) {
             more_args =
-                make_cons( va_arg( args, struct pso_pointer ), more_args );
+                make_cons( frame, va_arg( args, struct pso_pointer ),
+                           more_args );
         }
 
         frame->payload.stack_frame.more = c_reverse( more_args );
@@ -103,6 +105,8 @@ struct pso_pointer destroy_stack_frame( struct pso_pointer fp,
         dec_ref( frame->payload.stack_frame.previous );
         dec_ref( frame->payload.stack_frame.function );
         dec_ref( frame->payload.stack_frame.more );
+        dec_ref( frame->payload.stack_frame.locals );
+        dec_ref( frame->payload.stack_frame.env );
 
         for ( int i = 0; i < args_in_frame; i++ ) {
             dec_ref( frame->payload.stack_frame.arg[i] );
diff --git a/src/c/payloads/stack.h b/src/c/payloads/stack.h
index ed02588..e9ab776 100644
--- a/src/c/payloads/stack.h
+++ b/src/c/payloads/stack.h
@@ -31,10 +31,10 @@ struct stack_frame_payload {
     struct pso_pointer more;
     /** the function to be called. */
     struct pso_pointer function;
-	/** the execute-time environment */
-	struct pso_pointer env;
-	/** a list of objects created in the context of this frame */
-	struct pso_pointer locals;
+  /** the execute-time environment */
+    struct pso_pointer env;
+  /** a list of objects created in the context of this frame */
+    struct pso_pointer locals;
     /** the number of arguments provided. */
     uint32_t args;
     /** the depth of the stack below this frame */
diff --git a/src/c/payloads/write_stream.c b/src/c/payloads/write_stream.c
index 371f32c..1397e7a 100644
--- a/src/c/payloads/write_stream.c
+++ b/src/c/payloads/write_stream.c
@@ -15,6 +15,7 @@
 #include "memory/pointer.h"
 #include "memory/pso.h"
 #include "memory/pso2.h"
+#include "memory/pso4.h"
 #include "memory/tags.h"
 
 
@@ -24,9 +25,10 @@
  * @param metadata a pointer to an associaton containing metadata on the stream.
  * @return a pointer to the new read stream.
  */
-struct pso_pointer make_write_stream( URL_FILE *output,
+struct pso_pointer make_write_stream( struct pso4 *frame_pointer,
+                                      URL_FILE *output,
                                       struct pso_pointer metadata ) {
-    struct pso_pointer pointer = allocate( WRITETAG, 2 );
+    struct pso_pointer pointer = allocate( frame_pointer, WRITETAG, 2 );
     struct pso2 *cell = pointer_to_object( pointer );
 
     cell->payload.stream.stream = output;
diff --git a/src/c/payloads/write_stream.h b/src/c/payloads/write_stream.h
index 69de8a4..07e3b14 100644
--- a/src/c/payloads/write_stream.h
+++ b/src/c/payloads/write_stream.h
@@ -13,6 +13,7 @@
 /* write stream shares a payload with /see read_streem.h */
 
 #include "io/fopen.h"
-struct pso_pointer make_write_stream( URL_FILE * output,
+struct pso_pointer make_write_stream( struct pso4 *frame_pointer,
+                                      URL_FILE * output,
                                       struct pso_pointer metadata );
 #endif