imagetype: squash -Wsign-compare warning

diff --git a/lib/gvc/gvusershape.c b/lib/gvc/gvusershape.c
index 02da47cd20fe9cfb45b9e55a6fa3b5f1b0c64802..63b9f5d3076c67b2def2b6d98edd7c646ee034c7 100644 (file)
--- a/lib/gvc/gvusershape.c
+++ b/lib/gvc/gvusershape.c
@@ -81,10 +81,9 @@ static int imagetype (usershape_t *us)
 {
     char header[HDRLEN];
     char line[200];
-    int i;
 
     if (us->f && fread(header, 1, HDRLEN, us->f) == HDRLEN) {
-        for (i = 0; i < sizeof(knowntypes) / sizeof(knowntype_t); i++) {
+        for (size_t i = 0; i < sizeof(knowntypes) / sizeof(knowntype_t); i++) {
            if (!memcmp (header, knowntypes[i].template, knowntypes[i].size)) {
                us->stringtype = knowntypes[i].stringtype;
                us->type = knowntypes[i].type;