(uxnemu) Interrupt infinite loops with an error.

src/devices/system.c

@@ -20,7 +20,8 @@ static const char *errors[] = {
 	"Working-stack overflow",
 	"Return-stack overflow",
 	"Working-stack division by zero",
-	"Return-stack division by zero"};
+	"Return-stack division by zero",
+	"Execution timeout"};
 
 static void
 system_print(Stack *s, char *name)

src/uxn.c

@@ -30,16 +30,25 @@ WITH REGARD TO THIS SOFTWARE.
 #define DEVW8(x, y) { dev->dat[(x) & 0xf] = y; dev->deo(dev, (x) & 0x0f); }
 #define DEVW(d, x, y) { dev = (d); if(bs) { DEVW8((x), (y) >> 8); DEVW8((x) + 1, (y)); } else { DEVW8((x), (y)) } }
 #define WARP(x) { if(bs) pc = (x); else pc += (Sint8)(x); }
+#define LIMIT 0x40000 /* around 3 ms */
 
 int
 uxn_eval(Uxn *u, Uint16 pc)
 {
 	unsigned int a, b, c, j, k, bs, instr, errcode;
+	unsigned int limit = LIMIT;
 	Uint8 kptr, *sp;
 	Stack *src, *dst;
 	Device *dev;
 	if(!pc || u->dev[0].dat[0xf]) return 0;
 	while((instr = u->ram[pc++])) {
+		if(!limit--) {
+			if(!uxn_interrupt()) {
+				errcode = 6;
+				goto timeout;
+			}
+			limit = LIMIT;
+		}
 		/* Return Mode */
 		if(instr & 0x40) {
 			src = &u->rst; dst = &u->wst;
@@ -101,6 +110,7 @@ err:
 	/* set 1 in errcode if it involved the return stack instead of the working stack */
 	/*        (stack overflow & ( opcode was STH / JSR )) ^ Return Mode */
 	errcode |= ((errcode >> 1 & ((instr & 0x1e) == 0x0e)) ^ instr >> 6) & 1;
+timeout:
 	return uxn_halt(u, errcode, pc - 1);
 }
 

src/uxn.h

@@ -47,6 +47,7 @@ typedef struct Uxn {
 
 int uxn_boot(Uxn *u, Uint8 *ram);
 int uxn_eval(Uxn *u, Uint16 pc);
+int uxn_interrupt(void);
 int uxn_halt(Uxn *u, Uint8 error, Uint16 addr);
 Device *uxn_port(Uxn *u, Uint8 id, Uint8 (*deifn)(Device *, Uint8), void (*deofn)(Device *, Uint8));
 #endif /* UXN_UXN_H */

src/uxncli.c

@@ -101,6 +101,12 @@ load(Uxn *u, char *filepath)
 	return 1;
 }
 
+int
+uxn_interrupt(void)
+{
+	return 1;
+}
+
 static int
 start(Uxn *u)
 {

src/uxnemu.c

@@ -32,6 +32,7 @@ WITH REGARD TO THIS SOFTWARE.
 #define WIDTH 64 * 8
 #define HEIGHT 40 * 8
 #define PAD 4
+#define TIMEOUT_FRAMES 10
 
 static SDL_Window *gWindow;
 static SDL_Texture *gTexture;
@@ -43,7 +44,7 @@ static SDL_Rect gRect;
 
 static Device *devscreen, *devmouse, *devctrl, *devaudio0, *devfile0;
 static Uint8 zoom = 1;
-static Uint32 stdin_event, audio0_event, redraw_event;
+static Uint32 stdin_event, audio0_event, redraw_event, interrupt_event;
 
 static int
 error(char *msg, const char *err)
@@ -89,12 +90,19 @@ stdin_handler(void *p)
 static int
 redraw_handler(void *p)
 {
-	SDL_Event event;
+	int dropped_frames = 0;
+	SDL_Event event, interrupt;
 	event.type = redraw_event;
+	interrupt.type = interrupt_event;
 	for(;;) {
 		SDL_Delay(16);
-		if(SDL_HasEvent(redraw_event) == SDL_FALSE)
+		if(SDL_HasEvent(redraw_event) == SDL_FALSE) {
 			SDL_PushEvent(&event);
+			dropped_frames = 0;
+		}
+		else if(++dropped_frames == TIMEOUT_FRAMES) {
+			SDL_PushEvent(&interrupt);
+		}
 	}
 	return 0;
 	(void)p;
@@ -169,6 +177,7 @@ init(void)
 	stdin_event = SDL_RegisterEvents(1);
 	audio0_event = SDL_RegisterEvents(POLYPHONY);
 	redraw_event = SDL_RegisterEvents(1);
+	interrupt_event = SDL_RegisterEvents(1);
 	SDL_CreateThread(stdin_handler, "stdin", NULL);
 	SDL_CreateThread(redraw_handler, "redraw", NULL);
 	SDL_StartTextInput();
@@ -467,6 +476,12 @@ run(Uxn *u)
 	return error("SDL_WaitEvent", SDL_GetError());
 }
 
+int
+uxn_interrupt(void)
+{
+	return SDL_PeepEvents(NULL, 1, SDL_GETEVENT, interrupt_event, interrupt_event) < 1;
+}
+
 int
 main(int argc, char **argv)
 {