@@ -13,11 +13,17 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 WITH REGARD TO THIS SOFTWARE.

 */

-static const char *errors[] = {"underflow", "overflow", "division by zero"};

+static const char *errors[] = {

+	"Working-stack underflow",

+	"Return-stack underflow",

+	"Working-stack overflow",

+	"Return-stack overflow",

+	"Working-stack division by zero",

+	"Return-stack division by zero"};

 int

-uxn_halt(Uxn *u, Uint8 error, char *name, Uint16 addr)

+uxn_halt(Uxn *u, Uint8 error, Uint16 addr)

 {

-	fprintf(stderr, "Halted: %s %s#%04x, at 0x%04x\n", name, errors[error - 1], u->ram[addr], addr);

+	fprintf(stderr, "Halted: %s#%04x, at 0x%04x\n", errors[error], u->ram[addr], addr);

 	return 0;

 }

@@ -20,8 +20,8 @@ WITH REGARD TO THIS SOFTWARE.

 #define PUSH8(s, x) { if(s->ptr == 0xff) { errcode = 2; goto err; } s->dat[s->ptr++] = (x); }

 #define PUSH16(s, x) { if((j = s->ptr) >= 0xfe) { errcode = 2; goto err; } k = (x); s->dat[j] = k >> 8; s->dat[j + 1] = k; s->ptr = j + 2; }

 #define PUSH(s, x) { if(bs) { PUSH16(s, (x)) } else { PUSH8(s, (x)) } }

-#define POP8(o) { if(!(j = *sp)) { errcode = 1; goto err; } o = (Uint16)src->dat[--j]; *sp = j; }

-#define POP16(o) { if((j = *sp) <= 1) { errcode = 1; goto err; } o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }

+#define POP8(o) { if(!(j = *sp)) { errcode = 0; goto err; } o = (Uint16)src->dat[--j]; *sp = j; }

+#define POP16(o) { if((j = *sp) <= 1) { errcode = 0; goto err; } o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }

 #define POP(o) { if(bs) { POP16(o) } else { POP8(o) } }

 #define POKE(x, y) { if(bs) { u->ram[(x)] = (y) >> 8; u->ram[(x) + 1] = (y); } else { u->ram[(x)] = y; } }

 #define PEEK16(o, x) { o = (u->ram[(x)] << 8) + u->ram[(x) + 1]; }

@@ -89,7 +89,7 @@ uxn_eval(Uxn *u, Uint16 pc)

 		case 0x18: /* ADD */ POP(a) POP(b) PUSH(src, b + a) break;

 		case 0x19: /* SUB */ POP(a) POP(b) PUSH(src, b - a) break;

 		case 0x1a: /* MUL */ POP(a) POP(b) PUSH(src, (Uint32)b * a) break;

-		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) { errcode = 3; goto err; } PUSH(src, b / a) break;

+		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) { errcode = 4; goto err; } PUSH(src, b / a) break;

 		case 0x1c: /* AND */ POP(a) POP(b) PUSH(src, b & a) break;

 		case 0x1d: /* ORA */ POP(a) POP(b) PUSH(src, b | a) break;

 		case 0x1e: /* EOR */ POP(a) POP(b) PUSH(src, b ^ a) break;

@@ -99,10 +99,10 @@ uxn_eval(Uxn *u, Uint16 pc)

 	return 1;

 err:

-	if ((instr & 0x40 ? 1 : 0) ^ (errcode == 2 && ((instr & 0x1f) == 0x0e || (instr & 0x1f) == 0x0f)))

-		return uxn_halt(u, errcode, "Return-stack", pc - 1);

-	else

-		return uxn_halt(u, errcode, "Working-stack", pc - 1);

+	/* set 1 in errcode if it involved the return stack instead of the working stack */

+	/*        (stack overflow & (       instruction opcode was STH or JSR        )) ^ Return Mode */

+	errcode |= ((errcode >> 1 & instr >> 1 & instr >> 2 & instr >> 3 & ~instr >> 4) ^ instr >> 6) & 1;

+	return uxn_halt(u, errcode, pc - 1);

 }

 /* clang-format on */

@@ -45,5 +45,5 @@ typedef struct Uxn {

 int uxn_boot(Uxn *c, Uint8 *memory);

 int uxn_eval(Uxn *u, Uint16 pc);

-int uxn_halt(Uxn *u, Uint8 error, char *name, Uint16 addr);

+int uxn_halt(Uxn *u, Uint8 error, Uint16 addr);

 Device *uxn_port(Uxn *u, Uint8 id, Uint8 (*deifn)(Device *, Uint8), void (*deofn)(Device *, Uint8));