Still grinding incrementally forward, through barbed wire entanglements.

Morale fading.

src/c/payloads/cons.h

@@ -11,6 +11,7 @@
 #define __psse_payloads_cons_h
 #include <stdbool.h>
 
+#include "memory/node.h"
 #include "memory/pointer.h"
 #include "memory/pso2.h"
 #include "memory/pso4.h"
@@ -32,7 +33,7 @@ struct pso_pointer make_cons( struct pso_pointer frame_pointer,
                               struct pso_pointer car, struct pso_pointer cdr );
 
 /**
- * macro short-cuts for make_cons. 
+ * macro short-cuts for make_cons.
  */
 // #define make_cons(frame_pointer,car,cdr) (cons(make_frame(2, frame_pointer, car, cdr)))
 

src/c/payloads/stack.c

@@ -24,12 +24,46 @@
 
 #include "ops/reverse.h"
 #include "ops/list_ops.h"
+#include "ops/stack_ops.h"
+
+/**
+ * @brief Add an argument to this (already initialised) stack frame, updating
+ * the args count.
+ *
+ * TODO: unit test this to death and back!
+ *
+ * @param frame_pointer a pointer to the frame to be modified.
+ * @param arg_pointer the pointer to the arg to be added.
+ *
+ * @return `nil` on success; potentially an exception on failure.
+ */
+struct pso_pointer add_arg( struct pso_pointer frame_pointer, struct pso_pointer arg_pointer) {
+    struct pso4* frame = pointer_to_pso4( frame_pointer);
+    struct pso_pointer result = nil;
+
+    if (frame->payload.stack_frame.args < args_in_frame) {
+        frame->payload.stack_frame.arg[frame->payload.stack_frame.args++] = push_local(frame_pointer, arg_pointer);
+    } else {
+        struct pso_pointer new_more = c_reverse( frame_pointer,
+            make_cons( frame_pointer,
+                arg_pointer,
+                c_reverse( frame_pointer, frame->payload.stack_frame.more)));
+        if (exceptionp(new_more)) {
+            result = new_more;
+        } else {
+            frame->payload.stack_frame.more =
+                push_local( frame_pointer, new_more);
+        }
+    }
+
+    return result;
+}
 
 /**
  * @brief Construct a stack frame with this `previous` pointer, and arguments
  * taken from the remaining arguments to this function, which should all be
  * struct pso_pointer.
- * 
+ *
  * @param arg_count the count of arguments to the Lisp function.
  * @param previous the parent stack frame.
  * @param ... the arguments to the Lisp function, all of which must be of type
@@ -42,6 +76,9 @@ struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
     va_list args;
     va_start( args, previous );
 
+    /* NOTE! It is really important not to `push_local` the new_pointer here,
+     * since that would stop stack frames and all the temporary objects they
+     * curate ever being garbage collected! */
     struct pso_pointer new_pointer = allocate( previous, STACKTAG, 4 );
     struct pso4 *new_frame = pointer_to_pso4( new_pointer );
 
@@ -85,7 +122,7 @@ struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
                            more_args );
         }
 
-        new_frame->payload.stack_frame.more = c_reverse( more_args );
+        new_frame->payload.stack_frame.more = c_reverse( previous, more_args );
     } else {
         for ( ; cursor < args_in_frame; cursor++ ) {
             new_frame->payload.stack_frame.arg[cursor] = nil;
@@ -103,7 +140,10 @@ struct pso_pointer make_frame( int arg_count, struct pso_pointer previous,
  * @brief variant of make_frame with an explicit replacement environment, to
  * be called by functions like `binding` which add bindings to their upstack
  * environment.
- * 
+ *
+ * TODO: someone who really understood how C varargs functions work could save
+ * a lot of potentially error prone code by having this call `make_frame`, q.v.
+ *
  * @param arg_count the count of arguments to the Lisp function.
  * @param previous the parent stack frame.
  * @param env the modified environment
@@ -119,6 +159,9 @@ struct pso_pointer make_frame_with_env( int arg_count,
     va_start( args, env );
 
     struct pso4 *prev_frame = pointer_to_pso4( previous );
+    /* NOTE! It is really important not to `push_local` the new_pointer here,
+     * since that would stop stack frames and all the temporary objects they
+     * curate ever being garbage collected! */
     struct pso_pointer new_pointer = allocate( previous, STACKTAG, 4 );
     struct pso4 *new_frame = pointer_to_pso4( new_pointer );
 
@@ -159,7 +202,7 @@ struct pso_pointer make_frame_with_env( int arg_count,
                            more_args );
         }
 
-        new_frame->payload.stack_frame.more = c_reverse( more_args );
+        new_frame->payload.stack_frame.more = c_reverse( previous, more_args );
     } else {
         for ( ; cursor < args_in_frame; cursor++ ) {
             new_frame->payload.stack_frame.arg[cursor] = nil;
@@ -189,6 +232,9 @@ struct pso_pointer make_frame_with_arglist_and_env( struct pso_pointer
                                                     argvalues,
                                                     struct pso_pointer env ) {
     struct pso4 *prev_frame = pointer_to_pso4( previous );
+    /* NOTE! It is really important not to `push_local` the new_pointer here,
+     * since that would stop stack frames and all the temporary objects they
+     * curate ever being garbage collected! */
     struct pso_pointer new_pointer = allocate( previous, STACKTAG, 4 );
     struct pso4 *new_frame = pointer_to_pso4( new_pointer );
     struct pso_pointer arg_length =

src/c/payloads/stack.h

@@ -20,7 +20,7 @@
 #define args_in_frame 8
 
 /**
- * A stack frame. 
+ * A stack frame.
  */
 struct stack_frame_payload {
     /** the previous frame. */
@@ -60,4 +60,6 @@ struct pso_pointer make_frame_with_arglist( struct pso_pointer previous,
 struct pso_pointer destroy_stack_frame( struct pso_pointer fp,
                                         struct pso_pointer env );
 
+struct pso_pointer add_arg( struct pso_pointer frame_pointer, struct pso_pointer arg_pointer);
+
 #endif