Fix warning in musl related to ioctl

Ioctl's in musl take ints, while glibc take unsigned longs. When not
using glibc, default to casting the ioctl number to an int. Tests
passing.

test.sh

@@ -4,13 +4,17 @@ set -e
 # set -x # For debugging
 
 # If you ever mess this up:
-#  $ sudo mknod /dev/loop-control c 10 237
-#  $ sudo chmod 600 /dev/loop-control
-#  $ sudo chown root:root /dev/loop-control
+#  $ mknod /dev/loop-control c 10 237
+#  $ chmod 600 /dev/loop-control
+#  $ chown root:root /dev/loop-control
 #
 # For cleanup:
-#  $ sudo find /dev -maxdepth 1 -type b -name 'loop[0-9]*' -exec rm -f {} \;
+#  $ find /dev -maxdepth 1 -type b -name 'loop[0-9]*' -exec rm -f {} \;
 
+if [ "$(id -u)" -ne 0 ]; then
+    echo "Run as root. We need permissions to write and setup a loop device."
+    exit 1
+fi
 
 DISKFILE="/tmp/disk.img"
 BINFILE="/tmp/file.bin"
@@ -22,9 +26,9 @@ echo "Using device: ${LOOPDEV}"
 cleanup() {
     echo "Cleaning up..."
     set +e -x
-    sudo losetup -d ${LOOPDEV}
-    sudo rm ${LOOPDEV}
-    sudo rm ${BINFILE} ${DISKFILE}
+    losetup -d ${LOOPDEV}
+    rm ${LOOPDEV}
+    rm ${BINFILE} ${DISKFILE}
 }
 
 trap cleanup EXIT INT TERM
@@ -36,28 +40,31 @@ if losetup ${LOOPDEV} >/dev/null 2>&1; then
 fi
 
 if [ ! -f ${DISKFILE} ]; then
+    echo "Creating ${DISKFILE}"
     dd if=/dev/zero of=${DISKFILE} bs=1M count=256
 fi
 
 if [ ! -f ${BINFILE} ]; then
+    echo "Creating ${BINFILE}"
     dd if=/dev/urandom of=${BINFILE} bs=1M count=64
 fi
 
 if [ ! -e ${LOOPDEV} ]; then
-    sudo losetup ${LOOPDEV} ${DISKFILE}
+    mknod ${LOOPDEV} b 7 ${LOOPNUM} # busybox needs this
+    losetup ${LOOPDEV} ${DISKFILE}
 fi
 
-sudo ./writeimg -nd ${LOOPDEV} ${BINFILE}
-sudo ./writeimg -vnd ${LOOPDEV} ${BINFILE}
+./writeimg -nd ${LOOPDEV} ${BINFILE}
+./writeimg -vnd ${LOOPDEV} ${BINFILE}
 
-sudo ./writeimg -nd ${LOOPDEV} ./writeimg
-sudo ./writeimg -vnd ${LOOPDEV} ./writeimg
+./writeimg -nd ${LOOPDEV} ./writeimg
+./writeimg -vnd ${LOOPDEV} ./writeimg
 
-sudo ./writeimg -nd ${LOOPDEV} ./LICENSE
-sudo ./writeimg -vnd ${LOOPDEV} ./LICENSE
+./writeimg -nd ${LOOPDEV} ./LICENSE
+./writeimg -vnd ${LOOPDEV} ./LICENSE
 
 # Redirect this to avoid confusion
-! sudo ./writeimg -vnd ${LOOPDEV} ./crc32.h 2>/dev/null
+! ./writeimg -vnd ${LOOPDEV} ./crc32.h 2>/dev/null
 
 GREEN="\e[32m"
 RESET="\e[0m"

writeimg.c

@@ -278,7 +278,11 @@ int main(int argc, char *argv[]) {
             exit(EXIT_FAILURE);
         }
 
+#ifdef __GLIBC__
         if (ioctl(fd, BLKGETSIZE64, &device_size) < 0) {
+#else /* With musl, ioctl's take ints, kheaders provide unsigned longs. Passes tests. */
+        if (ioctl(fd, (int)BLKGETSIZE64, &device_size) < 0) {
+#endif
             perror("ioctl");
             close(fd);
             exit(EXIT_FAILURE);