Store getopt() return in a signed variable

On certain platforms [0] a char may be unsigned [1]. The loop for
getopt would loop forever because:

     (char)-1 => 255 and 255 != -1

A signed char also worked. I don't know what that would mean for
performance or portability. int feels simpler to me.

[0]: I'm using Arch Linux ARM on the Samsung Chromebook 2, which is
     armv7h. Not sure about other ARM platforms. With this fix, imv
     appears to work correctly.

     details: https://archlinuxarm.org/platforms/armv7/samsung/samsung-chromebook-2

[1]: http://stackoverflow.com/questions/2054939/is-char-signed-or-unsigned-by-default#2054941

1 files changed, 2 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index e73b205..fefd1ff 100644
--- a/src/main.c
+++ b/src/main.c
@@ -103,7 +103,8 @@ static void parse_args(int argc, char** argv)
   /* Do not print getopt errors */
   opterr = 0;
 
-  char *argp, *ep = *argv, o;
+  char *argp, *ep = *argv;
+  int o;
 
   while((o = getopt(argc, argv, "firasSudxhln:b:e:t:")) != -1) {
     switch(o) {