fail if input and output are the same

Originally committed as revision 23672 to svn://svn.ffmpeg.org/ffmpeg/trunk

tools/qt-faststart.c

@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <inttypes.h>
+#include <string.h>
 
 #ifdef __MINGW32__
 #define fseeko(x,y,z)  fseeko64(x,y,z)
@@ -98,6 +99,11 @@ int main(int argc, char *argv[])
         return 0;
     }
 
+    if (!strcmp(argv[1], argv[2])) {
+        fprintf(stderr, "input and output files need to be different\n");
+        return 1;
+    }
+
     infile = fopen(argv[1], "rb");
     if (!infile) {
         perror(argv[1]);