Fix GCC 7 -Wimplicit-fallthrough warnings.

dynasm/dasm_arm.h

@@ -254,6 +254,7 @@ void dasm_put(Dst_DECL, int start, ...)
       case DASM_IMMV8:
 	CK((n & 3) == 0, RANGE_I);
 	n >>= 2;
+	/* fallthrough */
       case DASM_IMML8:
       case DASM_IMML12:
 	CK(n >= 0 ? ((n>>((ins>>5)&31)) == 0) :
@@ -371,6 +372,7 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  break;
 	case DASM_REL_LG:
 	  CK(n >= 0, UNDEF_LG);
+	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);
 	  n = *DASM_POS2PTR(D, n) - (int)((char *)cp - base) - 4;

dynasm/dasm_mips.h

@@ -350,6 +350,7 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  break;
 	case DASM_REL_LG:
 	  CK(n >= 0, UNDEF_LG);
+	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);
 	  n = *DASM_POS2PTR(D, n);

dynasm/dasm_ppc.h

@@ -350,6 +350,7 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  break;
 	case DASM_REL_LG:
 	  CK(n >= 0, UNDEF_LG);
+	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);
 	  n = *DASM_POS2PTR(D, n) - (int)((char *)cp - base);

dynasm/dasm_x86.h

@@ -194,12 +194,13 @@ void dasm_put(Dst_DECL, int start, ...)
       switch (action) {
       case DASM_DISP:
 	if (n == 0) { if ((mrm&7) == 4) mrm = p[-2]; if ((mrm&7) != 5) break; }
-      case DASM_IMM_DB: if (((n+128)&-256) == 0) goto ob;
+	/* fallthrough */
+      case DASM_IMM_DB: if (((n+128)&-256) == 0) goto ob; /* fallthrough */
       case DASM_REL_A: /* Assumes ptrdiff_t is int. !x64 */
       case DASM_IMM_D: ofs += 4; break;
       case DASM_IMM_S: CK(((n+128)&-256) == 0, RANGE_I); goto ob;
       case DASM_IMM_B: CK((n&-256) == 0, RANGE_I); ob: ofs++; break;
-      case DASM_IMM_WB: if (((n+128)&-256) == 0) goto ob;
+      case DASM_IMM_WB: if (((n+128)&-256) == 0) goto ob; /* fallthrough */
       case DASM_IMM_W: CK((n&-65536) == 0, RANGE_I); ofs += 2; break;
       case DASM_SPACE: p++; ofs += n; break;
       case DASM_SETLABEL: b[pos-2] = -0x40000000; break;  /* Neg. label ofs. */
@@ -323,11 +324,14 @@ int dasm_link(Dst_DECL, size_t *szp)
 	  pos += 2;
 	  break;
 	}
+	  /* fallthrough */
 	case DASM_SPACE: case DASM_IMM_LG: case DASM_VREG: p++;
+	  /* fallthrough */
 	case DASM_DISP: case DASM_IMM_S: case DASM_IMM_B: case DASM_IMM_W:
 	case DASM_IMM_D: case DASM_IMM_WB: case DASM_IMM_DB:
 	case DASM_SETLABEL: case DASM_REL_A: case DASM_IMM_PC: pos++; break;
 	case DASM_LABEL_LG: p++;
+	  /* fallthrough */
 	case DASM_LABEL_PC: b[pos++] += ofs; break; /* Fix label offset. */
 	case DASM_ALIGN: ofs -= (b[pos++]+ofs)&*p++; break; /* Adjust ofs. */
 	case DASM_EXTERN: p += 2; break;
@@ -385,16 +389,20 @@ int dasm_encode(Dst_DECL, void *buffer)
 	    if (mrm != 5) { mm[-1] -= 0x80; break; } }
 	  if (((n+128) & -256) != 0) goto wd; else mm[-1] -= 0x40;
 	}
+	  /* fallthrough */
 	case DASM_IMM_S: case DASM_IMM_B: wb: dasmb(n); break;
 	case DASM_IMM_DB: if (((n+128)&-256) == 0) {
 	    db: if (!mark) mark = cp; mark[-2] += 2; mark = NULL; goto wb;
 	  } else mark = NULL;
+	  /* fallthrough */
 	case DASM_IMM_D: wd: dasmd(n); break;
 	case DASM_IMM_WB: if (((n+128)&-256) == 0) goto db; else mark = NULL;
+	  /* fallthrough */
 	case DASM_IMM_W: dasmw(n); break;
 	case DASM_VREG: { int t = *p++; if (t >= 2) n<<=3; cp[-1] |= n; break; }
 	case DASM_REL_LG: p++; if (n >= 0) goto rel_pc;
 	  b++; n = (int)(ptrdiff_t)D->globals[-n];
+	  /* fallthrough */
 	case DASM_REL_A: rel_a:
 	  n -= (unsigned int)(ptrdiff_t)(cp+4); goto wd; /* !x64 */
 	case DASM_REL_PC: rel_pc: {
@@ -407,6 +415,7 @@ int dasm_encode(Dst_DECL, void *buffer)
 	}
 	case DASM_IMM_LG:
 	  p++; if (n < 0) { n = (int)(ptrdiff_t)D->globals[-n]; goto wd; }
+	  /* fallthrough */
 	case DASM_IMM_PC: {
 	  int *pb = DASM_POS2PTR(D, n);
 	  n = *pb < 0 ? pb[1] : (*pb + (int)(ptrdiff_t)base);
@@ -427,6 +436,7 @@ int dasm_encode(Dst_DECL, void *buffer)
 	case DASM_EXTERN: n = DASM_EXTERN(Dst, cp, p[1], *p); p += 2; goto wd;
 	case DASM_MARK: mark = cp; break;
 	case DASM_ESC: action = *p++;
+	  /* fallthrough */
 	default: *cp++ = action; break;
 	case DASM_SECTION: case DASM_STOP: goto stop;
 	}

src/lj_asm.c

@@ -1725,6 +1725,7 @@ static void asm_setup_regsp(ASMState *as)
     case IR_SNEW: case IR_XSNEW: case IR_NEWREF:
       if (REGARG_NUMGPR < 3 && as->evenspill < 3)
 	as->evenspill = 3;  /* lj_str_new and lj_tab_newkey need 3 args. */
+      /* fallthrough */
     case IR_TNEW: case IR_TDUP: case IR_CNEW: case IR_CNEWI: case IR_TOSTR:
       ir->prev = REGSP_HINT(RID_RET);
       if (inloop)
@@ -1750,7 +1751,7 @@ static void asm_setup_regsp(ASMState *as)
 #endif
 	continue;
       }
-      /* fallthrough for integer POW */
+      /* fallthrough */ /* for integer POW */
     case IR_DIV: case IR_MOD:
       if (!irt_isnum(ir->t)) {
 	ir->prev = REGSP_HINT(RID_RET);

src/lj_cparse.c

@@ -590,28 +590,34 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	k->id = k2.id > k3.id ? k2.id : k3.id;
 	continue;
       }
+      /* fallthrough */
     case 1:
       if (cp_opt(cp, CTOK_OROR)) {
 	cp_expr_sub(cp, &k2, 2); k->i32 = k->u32 || k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 2:
       if (cp_opt(cp, CTOK_ANDAND)) {
 	cp_expr_sub(cp, &k2, 3); k->i32 = k->u32 && k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 3:
       if (cp_opt(cp, '|')) {
 	cp_expr_sub(cp, &k2, 4); k->u32 = k->u32 | k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 4:
       if (cp_opt(cp, '^')) {
 	cp_expr_sub(cp, &k2, 5); k->u32 = k->u32 ^ k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 5:
       if (cp_opt(cp, '&')) {
 	cp_expr_sub(cp, &k2, 6); k->u32 = k->u32 & k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 6:
       if (cp_opt(cp, CTOK_EQ)) {
 	cp_expr_sub(cp, &k2, 7); k->i32 = k->u32 == k2.u32; k->id = CTID_INT32;
@@ -620,6 +626,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	cp_expr_sub(cp, &k2, 7); k->i32 = k->u32 != k2.u32; k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 7:
       if (cp_opt(cp, '<')) {
 	cp_expr_sub(cp, &k2, 8);
@@ -654,6 +661,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	k->id = CTID_INT32;
 	continue;
       }
+      /* fallthrough */
     case 8:
       if (cp_opt(cp, CTOK_SHL)) {
 	cp_expr_sub(cp, &k2, 9); k->u32 = k->u32 << k2.u32;
@@ -666,6 +674,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
 	  k->u32 = k->u32 >> k2.u32;
 	continue;
       }
+      /* fallthrough */
     case 9:
       if (cp_opt(cp, '+')) {
 	cp_expr_sub(cp, &k2, 10); k->u32 = k->u32 + k2.u32;
@@ -675,6 +684,7 @@ static void cp_expr_infix(CPState *cp, CPValue *k, int pri)
       } else if (cp_opt(cp, '-')) {
 	cp_expr_sub(cp, &k2, 10); k->u32 = k->u32 - k2.u32; goto arith_result;
       }
+      /* fallthrough */
     case 10:
       if (cp_opt(cp, '*')) {
 	cp_expr_unary(cp, &k2); k->u32 = k->u32 * k2.u32; goto arith_result;

src/lj_err.c

@@ -153,6 +153,7 @@ static void *err_unwind(lua_State *L, void *stopcf, int errcode)
       if ((frame-1)->u32.lo == LJ_CONT_FFI_CALLBACK)
 	goto unwind_c;
 #endif
+      /* fallthrough */
     case FRAME_VARG:  /* Vararg frame. */
       frame = frame_prevd(frame);
       break;

src/lj_opt_sink.c

@@ -100,8 +100,8 @@ static void sink_mark_ins(jit_State *J)
 	   (LJ_32 && ir+1 < irlast && (ir+1)->o == IR_HIOP &&
 	    !sink_checkphi(J, ir, (ir+1)->op2))))
 	irt_setmark(ir->t);  /* Mark ineligible allocation. */
-      /* fallthrough */
 #endif
+      /* fallthrough */
     case IR_USTORE:
       irt_setmark(IR(ir->op2)->t);  /* Mark stored value. */
       break;

src/lj_parse.c

@@ -2696,7 +2696,8 @@ static int parse_stmt(LexState *ls)
       lj_lex_next(ls);
       parse_goto(ls);
       break;
-    }  /* else: fallthrough */
+    }
+    /* fallthrough */
   default:
     parse_call_assign(ls);
     break;

src/luajit.c

@@ -419,6 +419,7 @@ static int collectargs(char **argv, int *flags)
       break;
     case 'e':
       *flags |= FLAGS_EXEC;
+      /* fallthrough */
     case 'j':  /* LuaJIT extension */
     case 'l':
       *flags |= FLAGS_OPTION;