Allow nested use of PR_SaveParams()

PR_SaveParams() is required for implementing the +initialize diversion
used by Objective-QuakeC because builtins do not have local def spaces
(of course, a normal stack calling convention would help). However, it
is entirely possible for a call to +initialize to trigger another call
to +initialize, thus the need for stacking parameter stashes. As a
bonus, this implementation cleans up some fields in progs_t.

include/QF/progs.h

@@ -91,15 +91,63 @@ void PR_RunError (progs_t *pr, const char *error, ...) __attribute__((format(pri
 		(pr)->pr_params[1] = (pr)->pr_real_params[1];	\
 	} while (0)
 
-/** Save the current parameters.
+/**	\name Detouring Function Calls
-	\param pr		pointer to ::progs_t VM struct
+
+	These functions allow a builtin function that uses PR_CallFunction() to
+	safely insert a call to another VM function. The +initialize diversion
+	required by Objective-QuakeC uses this.
+
+		PR_PushFrame (pr);
+		__auto_type params = PR_SaveParams (pr);
+		... set up parameters to detour_function
+		PR_ExecuteProgram (pr, detour_function)
+		PR_RestoreParams (pr, params);
+		PR_PopFrame (pr);
+
 */
-void PR_SaveParams (progs_t *pr);
+///@{
+typedef struct pr_stashed_params_s {
+	pr_type_t  *param_ptrs[2];
+	int         argc;
+	pr_type_t   params[1];
+} pr_stashed_params_t;
+
+/** Save the current parameters to the provided stash.
+
+	\warning	The memory for the parameter stash is allocated using
+				alloca().
+
+	\param pr		pointer to ::progs_t VM struct
+	\return 		Pointer to a newly allocated and initialized parameter
+					stash that has the current parameters saved to it.
+	\hideinitializer
+*/
+#define PR_SaveParams(pr) \
+	_PR_SaveParams((pr), \
+				   alloca (field_offset (pr_stashed_params_t, \
+										 params[(pr)->pr_argc \
+												* (pr)->pr_param_size])))
+
+/** [INTERNAL] Save the current parameters to the provided stash.
+
+	\warning	Requires \a params to be correctly allocated. Use
+				PR_SaveParams instead as it will create a suitable stash for
+				saving the parameters.
+
+	\param pr		pointer to ::progs_t VM struct
+	\param params	location to save the parameters, must be of adequade size
+					to hold \a pr_argc * \a pr_param_size words in \a params
+	\return 		\a params Allows the likes of:
+						__auto_type params = PR_SaveParams (pr);
+*/
+pr_stashed_params_t *_PR_SaveParams (progs_t *pr, pr_stashed_params_t *params);
 
 /** Restore the parameters saved by PR_SaveParams().
 	\param pr		pointer to ::progs_t VM struct
+	\param params	pointer to stash created by PR_SaveParams()
 */
-void PR_RestoreParams (progs_t *pr);
+void PR_RestoreParams (progs_t *pr, pr_stashed_params_t *params);
+///@}
 
 /** Push an execution frame onto the VM stack. Saves current execution state.
 	\param pr		pointer to ::progs_t VM struct
@@ -1662,9 +1710,6 @@ struct progs_s {
 	pr_type_t  *pr_return;
 	pr_type_t  *pr_params[MAX_PARMS];
 	pr_type_t  *pr_real_params[MAX_PARMS];
-	pr_type_t  *pr_param_ptrs[2];
-	pr_type_t  *pr_saved_params;
-	int         pr_saved_argc;
 	int         pr_param_size;		///< covers both params and return
 	int         pr_param_alignment;	///< covers both params and return
 	///@}

libs/gamecode/pr_exec.c

@@ -72,37 +72,40 @@ PR_RunError (progs_t * pr, const char *error, ...)
 	PR_Error (pr, "Program error: %s", string->str);
 }
 
-VISIBLE void
+VISIBLE pr_stashed_params_t *
-PR_SaveParams (progs_t *pr)
+_PR_SaveParams (progs_t *pr, pr_stashed_params_t *params)
 {
 	int         i;
 	int         size = pr->pr_param_size * sizeof (pr_type_t);
 
-	pr->pr_param_ptrs[0] = pr->pr_params[0];
+	params->param_ptrs[0] = pr->pr_params[0];
-	pr->pr_param_ptrs[1] = pr->pr_params[1];
+	params->param_ptrs[1] = pr->pr_params[1];
 	pr->pr_params[0] = pr->pr_real_params[0];
 	pr->pr_params[1] = pr->pr_real_params[1];
 	for (i = 0; i < pr->pr_argc; i++) {
-		memcpy (pr->pr_saved_params + i * pr->pr_param_size,
+		memcpy (params->params + i * pr->pr_param_size,
 				pr->pr_real_params[i], size);
-		if (i < 2)
+		if (i < 2) { //XXX FIXME what the what?!?
-			memcpy (pr->pr_real_params[i], pr->pr_param_ptrs[0], size);
+			memcpy (pr->pr_real_params[i], params->param_ptrs[0], size);
+		}
 	}
-	pr->pr_saved_argc = pr->pr_argc;
+	params->argc = pr->pr_argc;
+	return params;
 }
 
 VISIBLE void
-PR_RestoreParams (progs_t *pr)
+PR_RestoreParams (progs_t *pr, pr_stashed_params_t *params)
 {
 	int         i;
 	int         size = pr->pr_param_size * sizeof (pr_type_t);
 
-	pr->pr_params[0] = pr->pr_param_ptrs[0];
+	pr->pr_params[0] = params->param_ptrs[0];
-	pr->pr_params[1] = pr->pr_param_ptrs[1];
+	pr->pr_params[1] = params->param_ptrs[1];
-	pr->pr_argc = pr->pr_saved_argc;
+	pr->pr_argc = params->argc;
-	for (i = 0; i < pr->pr_argc; i++)
+	for (i = 0; i < pr->pr_argc; i++) {
 		memcpy (pr->pr_real_params[i],
-				pr->pr_saved_params + i * pr->pr_param_size, size);
+				params->params + i * pr->pr_param_size, size);
+	}
 }
 
 VISIBLE inline void

libs/gamecode/pr_resolve.c

@@ -139,10 +139,6 @@ PR_ResolveGlobals (progs_t *pr)
 			goto error;
 		pr->pr_param_alignment = G_INT (pr, def->ofs);
 	}
-	if (pr->pr_saved_params)
-		free (pr->pr_saved_params);
-	pr->pr_saved_params = calloc (pr->pr_param_size * MAX_PARMS,
-								  sizeof (pr_type_t));
 	memcpy (pr->pr_real_params, pr->pr_params, sizeof (pr->pr_params));
 	if (!pr->globals.time) {
 		if ((def = PR_FindGlobal (pr, "time")))

libs/ruamoko/rua_obj.c

@@ -728,12 +728,12 @@ obj_send_initialize (progs_t *pr, pr_class_t *class)
 			sel = &G_STRUCT (pr, pr_sel_t, method->method_name);
 			if (sel->sel_id == selector->sel_id) {
 				PR_PushFrame (pr);
-				PR_SaveParams (pr);
+				__auto_type params = PR_SaveParams (pr);
 				// param 0 is known to be the class pointer
 				P_POINTER (pr, 1) = method->method_name;
 				// pr->pr_argc is known to be 2
 				PR_ExecuteProgram (pr, method->method_imp);
-				PR_RestoreParams (pr);
+				PR_RestoreParams (pr, params);
 				PR_PopFrame (pr);
 				return;
 			}