fix compile warning

diff --git a/ext/standard/mail.c b/ext/standard/mail.c
index db5658c26eb51d57df48daaa70aad26e119d9ab2..6c5f3ec9cf20f702aa447d656bf02344ea1de4c9 100644 (file)
--- a/ext/standard/mail.c
+++ b/ext/standard/mail.c
@@ -58,7 +58,7 @@
 #define MAIL_ASCIIZ_CHECK(str, len)                    \
        p = str;                                        \
        e = p + len;                                    \
-       while (p = memchr(p, '\0', (e - p))) {          \
+       while ((p = memchr(p, '\0', (e - p)))) {        \
                *p = ' ';                               \
        }                                               \