lib: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix multiple
warnings by explicitly adding multiple break statements instead of
letting the code fall through to the next case, and by replacing a
number of /* fall through */ comments with the new pseudo-keyword
macro fallthrough.

Notice that Clang doesn't recognize /* Fall through */ comments as
implicit fall-through markings.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

lib/cmdline.c

@@ -153,6 +153,7 @@ unsigned long long memparse(const char *ptr, char **retptr)
 	case 'k':
 		ret <<= 10;
 		endptr++;
+		fallthrough;
 	default:
 		break;
 	}

lib/kstrtox.c

@@ -363,6 +363,7 @@ int kstrtobool(const char *s, bool *res)
 		default:
 			break;
 		}
+		break;
 	default:
 		break;
 	}

lib/nlattr.c

@@ -434,7 +434,7 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 			err = -EINVAL;
 			goto out_err;
 		}
-		/* fall through */
+		fallthrough;
 
 	case NLA_STRING:
 		if (attrlen < 1)

lib/vsprintf.c

@@ -2530,6 +2530,7 @@ qualifier:
 	case 'd':
 	case 'i':
 		spec->flags |= SIGN;
+		break;
 	case 'u':
 		break;
 

lib/zlib_inflate/inflate.c

@@ -396,7 +396,7 @@ int zlib_inflate(z_streamp strm, int flush)
             strm->adler = state->check = REVERSE(hold);
             INITBITS();
             state->mode = DICT;
-	    /* fall through */
+	    fallthrough;
         case DICT:
             if (state->havedict == 0) {
                 RESTORE();
@@ -404,10 +404,10 @@ int zlib_inflate(z_streamp strm, int flush)
             }
             strm->adler = state->check = zlib_adler32(0L, NULL, 0);
             state->mode = TYPE;
-	    /* fall through */
+	    fallthrough;
         case TYPE:
             if (flush == Z_BLOCK) goto inf_leave;
-	    /* fall through */
+	    fallthrough;
         case TYPEDO:
             INFLATE_TYPEDO_HOOK(strm, flush);
             if (state->last) {
@@ -446,7 +446,7 @@ int zlib_inflate(z_streamp strm, int flush)
             state->length = (unsigned)hold & 0xffff;
             INITBITS();
             state->mode = COPY;
-	    /* fall through */
+	    fallthrough;
         case COPY:
             copy = state->length;
             if (copy) {
@@ -480,7 +480,7 @@ int zlib_inflate(z_streamp strm, int flush)
 #endif
             state->have = 0;
             state->mode = LENLENS;
-	    /* fall through */
+	    fallthrough;
         case LENLENS:
             while (state->have < state->ncode) {
                 NEEDBITS(3);
@@ -501,7 +501,7 @@ int zlib_inflate(z_streamp strm, int flush)
             }
             state->have = 0;
             state->mode = CODELENS;
-	    /* fall through */
+	    fallthrough;
         case CODELENS:
             while (state->have < state->nlen + state->ndist) {
                 for (;;) {
@@ -575,7 +575,7 @@ int zlib_inflate(z_streamp strm, int flush)
                 break;
             }
             state->mode = LEN;
-	    /* fall through */
+	    fallthrough;
         case LEN:
             if (have >= 6 && left >= 258) {
                 RESTORE();
@@ -615,7 +615,7 @@ int zlib_inflate(z_streamp strm, int flush)
             }
             state->extra = (unsigned)(this.op) & 15;
             state->mode = LENEXT;
-	    /* fall through */
+	    fallthrough;
         case LENEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -623,7 +623,7 @@ int zlib_inflate(z_streamp strm, int flush)
                 DROPBITS(state->extra);
             }
             state->mode = DIST;
-	    /* fall through */
+	    fallthrough;
         case DIST:
             for (;;) {
                 this = state->distcode[BITS(state->distbits)];
@@ -649,7 +649,7 @@ int zlib_inflate(z_streamp strm, int flush)
             state->offset = (unsigned)this.val;
             state->extra = (unsigned)(this.op) & 15;
             state->mode = DISTEXT;
-	    /* fall through */
+	    fallthrough;
         case DISTEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -669,7 +669,7 @@ int zlib_inflate(z_streamp strm, int flush)
                 break;
             }
             state->mode = MATCH;
-	    /* fall through */
+	    fallthrough;
         case MATCH:
             if (left == 0) goto inf_leave;
             copy = out - left;
@@ -720,7 +720,7 @@ int zlib_inflate(z_streamp strm, int flush)
                 INITBITS();
             }
             state->mode = DONE;
-	    /* fall through */
+	    fallthrough;
         case DONE:
             ret = Z_STREAM_END;
             goto inf_leave;

lib/zstd/bitstream.h

@@ -269,6 +269,7 @@ ZSTD_STATIC size_t BIT_initDStream(BIT_DStream_t *bitD, const void *srcBuffer, s
 		case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16;
 			/* fall through */
 		case 2: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[1]) << 8;
+			fallthrough;
 		default:;
 		}
 		{

lib/zstd/huf_compress.c

@@ -560,6 +560,7 @@ size_t HUF_compress1X_usingCTable(void *dst, size_t dstSize, const void *src, si
 	case 2: HUF_encodeSymbol(&bitC, ip[n + 1], CTable); HUF_FLUSHBITS_1(&bitC);
 		/* fall through */
 	case 1: HUF_encodeSymbol(&bitC, ip[n + 0], CTable); HUF_FLUSHBITS(&bitC);
+		fallthrough;
 	case 0:
 	default:;
 	}