Clean up compile warnings and default to -Wall.

Hopefully this will make introducing new bugs more obvious.

Makefile

@@ -5,7 +5,7 @@ config.mk:
 	$(MAKE) shairport
 endif
 
-CFLAGS ?= -O2
+CFLAGS ?= -O2 -Wall
 -include config.mk
 
 PREFIX ?= /usr/local

audio_pipe.c

@@ -44,7 +44,7 @@ static void start(int sample_rate) {
 }
 
 static void play(short buf[], int samples) {
-    write(fd, buf, samples*4);
+    write_unchecked(fd, buf, samples*4);
 }
 
 static void stop(void) {

common.c

@@ -28,6 +28,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <memory.h>
+#include <unistd.h>
 #include <openssl/rsa.h>
 #include <openssl/pem.h>
 #include <openssl/evp.h>

common.h

@@ -40,6 +40,13 @@ void die(char *format, ...);
 void warn(char *format, ...);
 void debug(int level, char *format, ...);
 
+/* functions that ignore return values without compiler warnings.
+ * for use only where return values really don't matter!
+ */
+#define write_unchecked(...) (void)(write(__VA_ARGS__)+1)
+#define read_unchecked(...)  (void)(read (__VA_ARGS__)+1)
+#define lockf_unchecked(...) (void)(lockf(__VA_ARGS__)+1)
+
 uint8_t *base64_dec(char *input, int *outlen);
 char *base64_enc(uint8_t *input, int length);
 

daemon.c

@@ -56,7 +56,7 @@ void daemon_init() {
             exit(1);
         } else if (buf[0] != 0) {
             // First byte is non zero, child sent error message
-            write(STDERR_FILENO, buf, ret);
+            write_unchecked(STDERR_FILENO, buf, ret);
             fprintf(stderr, "\n");
             exit(1);
         } else {
@@ -86,7 +86,7 @@ void daemon_init() {
 
 void daemon_ready() {
     char ok = 0;
-    write(daemon_pipe[1], &ok, 1);
+    write_unchecked(daemon_pipe[1], &ok, 1);
     close(daemon_pipe[1]);
     daemon_pipe[1] = -1;
 }
@@ -100,7 +100,7 @@ void daemon_fail(const char *format, va_list arg) {
 
 void daemon_exit() {
     if (lock_fd > 0) {
-        lockf(lock_fd, F_ULOCK, 0);
+        lockf_unchecked(lock_fd, F_ULOCK, 0);
         close(lock_fd);
         unlink(config.pidfile);
         lock_fd = -1;

mdns_external.c

@@ -64,7 +64,7 @@ static int fork_execvp(const char *file, char *const argv[]) {
 
         // If we reach this point then execve has failed.
         // Write erno's value into the pipe and exit.
-        write(execpipe[1], &errno, sizeof(errno));
+        write_unchecked(execpipe[1], &errno, sizeof(errno));
 
         _exit(-1);
         return 0; // Just to make the compiler happy.

rtsp.c

@@ -356,7 +356,7 @@ static void msg_write_response(int fd, rtsp_message *resp) {
         die("Attempted to write overlong RTSP packet");
 
     strcpy(p, "\r\n");
-    write(fd, pkt, p-pkt+2);
+    write_unchecked(fd, pkt, p-pkt+2);
 }
 
 static void handle_options(rtsp_conn_info *conn,
@@ -590,7 +590,7 @@ static char *make_nonce(void) {
     int fd = open("/dev/random", O_RDONLY);
     if (fd < 0)
         die("could not open /dev/random!");
-    read(fd, random, sizeof(random));
+    read_unchecked(fd, random, sizeof(random));
     close(fd);
     return base64_enc(random, 8);
 }