add generic terminal prompt function

diff --git a/xdiff/xmerge.c b/xdiff/xmerge.c
index 6d6fc1bc5e01be7305ec5101f43645a1dce69bd3..9e13b25abc90350de4488276074dc282edc216b1 100644 (file)
--- a/xdiff/xmerge.c
+++ b/xdiff/xmerge.c
@@ -336,7 +336,7 @@ static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
 static int line_contains_alnum(const char *ptr, long size)
 {
        while (size--)
-               if (isalnum(*(ptr++)))
+               if (isalnum((unsigned char)*(ptr++)))
                        return 1;
        return 0;
 }