fix ENDPROC inside a loop causing loop-stack exhaustion

Author: braindigitalis

include/basic/context.h

@@ -24,6 +24,12 @@ typedef struct basic_sound_t {
 	struct basic_sound_t* next;	/* Next */
 } basic_sound_t;
 
+typedef struct control_stack_state {
+	uint64_t for_stack_ptr;
+	uint64_t while_stack_ptr;
+	uint64_t repeat_stack_ptr;
+} control_stack_state;
+
 /**
  * @brief BASIC program context.
  *
@@ -198,6 +204,11 @@ typedef struct basic_ctx {
 	 */
 	int64_t eval_linenum;
 
+	/**
+	 * @brief The saved loop pointer state when entering PROC
+	 */
+	control_stack_state loop_state_stack[MAX_CALL_STACK_DEPTH];
+
 	/**
 	 * @brief FOR loop stack to handle `FOR...NEXT` loops.
 	 *

modules/xm/xm.c

@@ -1591,7 +1591,7 @@ static bool xm_from_memory(const char *filename, const void *bytes, size_t len,
  * @return true on success, false on failure.
  */
 bool EXPORTED MOD_INIT_SYM(KMOD_ABI)(void) {
-	dprintf("xm: loaded - this module is experimental. There may be audio artifacts.\n");
+	dprintf("xm: loaded\n");
 
 	audio_file_loader_t *loader = (audio_file_loader_t *) kmalloc(sizeof(audio_file_loader_t));
 	if (!loader) {

src/basic/function.c

@@ -668,6 +668,9 @@ void proc_statement(struct basic_ctx* ctx)
 
 		ctx->fn_type_stack[ctx->call_stack_ptr] = ctx->fn_type; // save caller’s type
 		ctx->fn_type = RT_NONE;
+		ctx->loop_state_stack[ctx->call_stack_ptr].for_stack_ptr = ctx->for_stack_ptr;
+		ctx->loop_state_stack[ctx->call_stack_ptr].while_stack_ptr = ctx->while_stack_ptr;
+		ctx->loop_state_stack[ctx->call_stack_ptr].repeat_stack_ptr = ctx->repeat_stack_ptr;
 
 		while (tokenizer_token(ctx) != NEWLINE && tokenizer_token(ctx) != ENDOFINPUT) {
 			tokenizer_next(ctx);
@@ -744,6 +747,12 @@ void endproc_statement(struct basic_ctx* ctx)
 
 		/* Now restore the *caller*'s return type. */
 		ctx->fn_type = ctx->fn_type_stack[ctx->call_stack_ptr];
+		while (ctx->for_stack_ptr > ctx->loop_state_stack[ctx->call_stack_ptr].for_stack_ptr) {
+			ctx->for_stack_ptr--;
+			buddy_free(ctx->allocator, ctx->for_stack[ctx->for_stack_ptr].for_variable);
+		}
+		ctx->while_stack_ptr = ctx->loop_state_stack[ctx->call_stack_ptr].while_stack_ptr;
+		ctx->repeat_stack_ptr = ctx->loop_state_stack[ctx->call_stack_ptr].repeat_stack_ptr;
 
 		ctx->if_nest_level = 0; // If we exit a proc, we clear the nest level