Polish code

code issues found by Clang with
CFLAGS="-Os -Wall -Wextra -Werror=unused-const-variable -Wno-error=unused-parameter"
enabled

The details as follows:
- variable initialization issue, modified them as Clang suggested
- data type mismatch when comparing, fix them either by casting or changing
  the data type of index of iterator
- get_sockaddr() in netutils may return -1 thus changed returning type from
  size_t to ssize_t, which makes Clang happier
- recvfrom() in udprelay is identical, fix this by creating local variable
  for comparison  and assign back to buf->len when returning value is acceptable

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

src/encrypt.c

@@ -203,7 +203,8 @@ static int safe_memcmp(const void *s1, const void *s2, size_t n)
 {
     const unsigned char *_s1 = (const unsigned char *)s1;
     const unsigned char *_s2 = (const unsigned char *)s2;
-    int ret                  = 0, i;
+    int ret                  = 0;
+    size_t i;
     for (i = 0; i < n; i++)
         ret |= _s1[i] ^ _s2[i];
     return !!ret;
@@ -219,7 +220,7 @@ int balloc(buffer_t *ptr, size_t capacity)
 
 int brealloc(buffer_t *ptr, size_t len, size_t capacity)
 {
-    int real_capacity = max(len, capacity);
+    size_t real_capacity = max(len, capacity);
     if (ptr->capacity < real_capacity) {
         ptr->array    = realloc(ptr->array, real_capacity);
         ptr->capacity = real_capacity;
@@ -1119,7 +1120,7 @@ int ss_encrypt_all(buffer_t *plain, int method, int auth, size_t capacity)
         size_t iv_len = enc_iv_len;
         int err       = 1;
 
-        static buffer_t tmp = { 0 };
+        static buffer_t tmp = { 0, 0, 0, NULL };
         brealloc(&tmp, iv_len + plain->len, capacity);
         buffer_t *cipher = &tmp;
         cipher->len = plain->len;
@@ -1178,7 +1179,7 @@ int ss_encrypt_all(buffer_t *plain, int method, int auth, size_t capacity)
 int ss_encrypt(buffer_t *plain, enc_ctx_t *ctx, size_t capacity)
 {
     if (ctx != NULL) {
-        static buffer_t tmp = { 0 };
+        static buffer_t tmp = { 0, 0, 0, NULL };
 
         int err       = 1;
         size_t iv_len = 0;
@@ -1261,7 +1262,7 @@ int ss_decrypt_all(buffer_t *cipher, int method, int auth, size_t capacity)
         cipher_ctx_t evp;
         cipher_context_init(&evp, method, 0);
 
-        static buffer_t tmp = { 0 };
+        static buffer_t tmp = { 0, 0, 0, NULL };
         brealloc(&tmp, cipher->len, capacity);
         buffer_t *plain = &tmp;
         plain->len = cipher->len - iv_len;
@@ -1324,7 +1325,7 @@ int ss_decrypt_all(buffer_t *cipher, int method, int auth, size_t capacity)
 int ss_decrypt(buffer_t *cipher, enc_ctx_t *ctx, size_t capacity)
 {
     if (ctx != NULL) {
-        static buffer_t tmp = { 0 };
+        static buffer_t tmp = { 0, 0, 0, NULL };
 
         size_t iv_len = 0;
         int err       = 1;