Add JQ_FALLTHROUGH and use it to quiet warnings

src/execute.c

@@ -575,6 +575,7 @@ jv jq_next(jq_state *jq) {
 
     case STOREVN:
         stack_save(jq, pc - 1, stack_get_pos(jq));
+        JQ_FALLTHROUGH;
     case STOREV: {
       uint16_t level = *pc++;
       uint16_t v = *pc++;
@@ -742,7 +743,7 @@ jv jq_next(jq_state *jq) {
       }
       stack_push(jq, container);
       stack_push(jq, jv_number(-1));
-      // fallthrough
+      JQ_FALLTHROUGH;
     }
     case ON_BACKTRACK(EACH):
     case ON_BACKTRACK(EACH_OPT): {

src/jv.c

@@ -1222,7 +1222,9 @@ static uint32_t jvp_string_hash(jv jstr) {
 
   switch(len & 3) {
   case 3: k1 ^= tail[2] << 16;
+          JQ_FALLTHROUGH;
   case 2: k1 ^= tail[1] << 8;
+          JQ_FALLTHROUGH;
   case 1: k1 ^= tail[0];
           k1 *= c1; k1 = rotl32(k1,15); k1 *= c2; h1 ^= k1;
   }

src/jv.h

@@ -5,6 +5,13 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#if (defined(__GNUC__) && __GNUC__ >= 7) || \
+    (defined(__clang__) && __clang_major__ >= 10)
+# define JQ_FALLTHROUGH __attribute__((fallthrough))
+#else
+# define JQ_FALLTHROUGH do {} while (0) /* fallthrough */
+#endif
+
 typedef enum {
   JV_KIND_INVALID,
   JV_KIND_NULL,

src/jv_dtoa.c

@@ -195,6 +195,7 @@
 #include "jv_dtoa.h"
 
 #include "jv_alloc.h"
+#include "jv.h"
 #define MALLOC jv_mem_alloc
 #define FREE jv_mem_free
 
@@ -1723,6 +1724,7 @@ gethex(struct dtoa_context* C,  CONST char **sp, U *rvp, int rounding, int sign)
 		  case '-':
 			esign = 1;
 			/* no break */
+			JQ_FALLTHROUGH;
 		  case '+':
 			s++;
 		  }
@@ -2327,7 +2329,10 @@ retlow1:
 jvp_strtod
  (struct dtoa_context* C, const char *s00, char **se)
 {
-	int bb2, bb5, bbe, bd2, bd5, bbbits, bs2, c, e, e1, test_scale;
+	int bb2, bb5, bbe, bd2, bd5, bbbits, bs2, c, e, e1;
+#ifdef Honor_FLT_ROUNDS
+	int test_scale;
+#endif
 	int esign, i, j, k, nd, nd0, nf, nz, nz0, nz1, sign;
 	CONST char *s, *s0, *s1;
 	double aadj, aadj1;
@@ -2367,10 +2372,12 @@ jvp_strtod
 		case '-':
 			sign = 1;
 			/* no break */
+			JQ_FALLTHROUGH;
 		case '+':
 			if (*++s)
 				goto break2;
 			/* no break */
+			JQ_FALLTHROUGH;
 		case 0:
 			goto ret0;
 		case '\t':
@@ -2478,6 +2485,7 @@ jvp_strtod
 		switch(c = *++s) {
 			case '-':
 				esign = 1;
+				JQ_FALLTHROUGH;
 			case '+':
 				c = *++s;
 			}
@@ -3699,6 +3707,7 @@ jvp_dtoa
 		case 2:
 			leftright = 0;
 			/* no break */
+			JQ_FALLTHROUGH;
 		case 4:
 			if (ndigits <= 0)
 				ndigits = 1;
@@ -3707,6 +3716,7 @@ jvp_dtoa
 		case 3:
 			leftright = 0;
 			/* no break */
+			JQ_FALLTHROUGH;
 		case 5:
 			i = ndigits + k + 1;
 			ilim = i;