Increase compiler warning level

...and fix the resulting warnings.

Author: mthuurne

Makefile

@@ -1,4 +1,5 @@
-CFLAGS ?= -std=c99 -Wall -O2 -fomit-frame-pointer
+CFLAGS = -std=c99 -O2 -fomit-frame-pointer
+CFLAGS += -Wall -Wextra -Wundef -Wold-style-definition
 LDFLAGS = -s -static
 
 BINARIES = mininit-initramfs mininit-syspart splashkill

initramfs.c

@@ -53,7 +53,7 @@ static int multi_mount(
 	return -1;
 }
 
-const char *mount_boot()
+const char *mount_boot(void)
 {
 	/* Create boot and root mount points.
 	 * Failure is most likely fatal, but perhaps mkdir on a usable mount point
@@ -77,7 +77,7 @@ const char *mount_boot()
 	return boot_mount;
 }
 
-int open_dir_to_clean()
+int open_dir_to_clean(void)
 {
 	int fd = open("/", O_PATH | O_DIRECTORY);
 	if (fd < 0) {
@@ -86,7 +86,7 @@ int open_dir_to_clean()
 	return fd;
 }
 
-int switch_root()
+int switch_root(void)
 {
 	DEBUG("Switching root\n");
 

loop.c

@@ -9,7 +9,7 @@
 #include "loop.h"
 
 
-int logetfree()
+int logetfree(void)
 {
 	int fd = open("/dev/loop-control", O_RDWR);
 	if (fd < 0) {

loop.h

@@ -5,7 +5,7 @@
  * Find or allocate a free loop device.
  * Returns the minor block device number (0-255), or -1 on errors.
  */
-int logetfree();
+int logetfree(void);
 
 /**
  * Set the given file as a backing file for the given loop device.

mininit.h

@@ -14,18 +14,18 @@ int create_mount_point(const char *path);
  * is mounted.
  * Returns the mount point of the boot partition on success and NULL on errors.
  */
-const char *mount_boot();
+const char *mount_boot(void);
 
 /**
  * Returns a file descriptor for the directory to be cleaned up before we exec.
  * If there is nothing to clean up, return -1.
  * If there was an error opening the directory, return -1 as well.
  */
-int open_dir_to_clean();
+int open_dir_to_clean(void);
 
 /**
  * Make the current directory the root directory and preserve the boot partition
  * in the "boot" subdirectory of the current directory.
  * Returns 0 on success and -1 on errors.
  */
-int switch_root();
+int switch_root(void);

splashkill.c

@@ -31,7 +31,7 @@ static void quit_hdl(int err)
 	exit(err);
 }
 
-static int waitForEnter()
+static int waitForEnter(void)
 {
 	fd = open(event_fn, O_RDONLY);
 	if (fd < 0) {
@@ -60,6 +60,7 @@ int main(int argc, char **argv)
 	if (fork())
 		execl(init_fn, "/init", NULL);
 
+	(void)argc;
 	strlcpy(argv[0], process_name, strlen(argv[0]));
 
 	int res = waitForEnter();

syspart.c

@@ -10,17 +10,17 @@
 #include "mininit.h"
 
 
-const char *mount_boot()
+const char *mount_boot(void)
 {
 	return "/";
 }
 
-int open_dir_to_clean()
+int open_dir_to_clean(void)
 {
 	return -1;
 }
 
-int switch_root()
+int switch_root(void)
 {
 	DEBUG("Pivoting root\n");
 	if (syscall(SYS_pivot_root, ".", "boot")) {