Bug#871094: Patch to fix GCC 7 build failures

[Johannes Brandstätter]

tags 871094 + patch
thanks

The attached patch fixes the implicit fallthrough warnings and an
uninitialized variable.
--- a/src/bloc.c
+++ b/src/bloc.c
@@ -1249,6 +1249,7 @@
     case MEM_SET_SIZE:
         u32 = args;
         bd->trks = (*u32 + bd->seclen - 1) / bd->seclen + 1;
+        __attribute__((fallthrough));
     default:
         ret = -1;
         break;
--- a/src/char.c
+++ b/src/char.c
@@ -154,6 +154,7 @@
             CHARDEV_DPRINTF("one serial port\n");
             register_outd = 1;
             /* No break here */
+            __attribute__((fallthrough));
         case CHARDEV_KBD:
             CHARDEV_DPRINTF("one input port %d %d\n", n, i);
             if (i < 16 && chardev_open(cur) == 0) {
@@ -162,6 +163,7 @@
             if (!register_outd)
                 break;
             /* No break here */
+            __attribute__((fallthrough));
         case CHARDEV_DISPLAY:
             CHARDEV_DPRINTF("one output port %d %d\n", n, j);
             if (j < 16 && chardev_open(cur) == 0) {
@@ -587,6 +589,7 @@
     case ADB_LISTEN:
         memcpy(adb_send + 1, buf, len);
         /* No break here */
+        __attribute__((fallthrough));
     case ADB_TALK:
         adb_send[0] = (dev->addr << 4) | cmd | reg;
         break;
--- a/src/libc/src/format.c
+++ b/src/libc/src/format.c
@@ -281,6 +281,7 @@
                 goto next;
             }
             /* No break here */
+            __attribute__((fallthrough));
         case '1' ... '9':
             switch (maxfill) {
             case -2:
@@ -350,6 +351,7 @@
                 goto invalid;
             } else {
                 tmp = outc(outf, private, '%', maxlen - totlen);
+                __attribute__((fallthrough));
             }
         default:
         invalid:
--- a/src/of.c
+++ b/src/of.c
@@ -3000,7 +3000,7 @@
 {
     OF_env_t *OF_env = OF_env_main;
     OF_node_t *pci_ata = dev;
-    OF_node_t *ata, *atas[2];
+    OF_node_t *ata, *atas[2] = { NULL };
     int i;
 
     OF_prop_int_new(OF_env, pci_ata, "#address-cells", 1);