Fixed some warnings when building on Linux with -DSDL_LIBC=OFF

src/SDL_log.c

@@ -496,6 +496,11 @@ SDL_LogOutput(void *userdata, int category, SDL_LogPriority priority,
 #if HAVE_STDIO_H && \
     !(defined(__APPLE__) && (defined(SDL_VIDEO_DRIVER_COCOA) || defined(SDL_VIDEO_DRIVER_UIKIT)))
     fprintf(stderr, "%s: %s\n", SDL_priority_prefixes[priority], message);
+#else
+    /* We won't print anything, but reference the priority prefix anyway
+       to avoid a compiler warning.
+     */
+    (void)SDL_priority_prefixes[priority];
 #endif
 }
 

src/filesystem/unix/SDL_sysfilesystem.c

@@ -25,14 +25,14 @@
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 /* System dependent filesystem routines                                */
 
-#include <errno.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <limits.h>
+#include <errno.h>
 #include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 #if defined(__FREEBSD__) || defined(__OPENBSD__)
 #include <sys/sysctl.h>

src/hidapi/SDL_hidapi.c

@@ -63,7 +63,8 @@
 
 #ifdef HAVE_INOTIFY
 #include <unistd.h>  /* just in case we didn't use that SDL_USE_LIBUDEV block... */
-#include <errno.h>              /* errno, strerror */
+#include <string.h>             /* strerror */
+#include <errno.h>              /* errno */
 #include <fcntl.h>
 #include <limits.h>             /* For the definition of NAME_MAX */
 #include <sys/inotify.h>