expr: Add const qualifiers to *2str translation arrays

Add const qualifiers to the "to string" translation arrays used by
various *2str() functions.

This fixes GCC warnings such as the following when compiling with
-Wwrite-strings:

  expr/byteorder.c:176:25: warning: initialization discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]

In order to catch these in the future, also add -Wwrite-strings to
default CFLAGS.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/expr/byteorder.c b/src/expr/byteorder.c
index 5f8e585..3805307 100644
--- a/src/expr/byteorder.c
+++ b/src/expr/byteorder.c
@@ -172,7 +172,7 @@ nftnl_expr_byteorder_parse(struct nftnl_expr *e, struct nlattr *attr)
 	return ret;
 }
 
-static char *expr_byteorder_str[] = {
+static const char *expr_byteorder_str[] = {
 	[NFT_BYTEORDER_HTON] = "hton",
 	[NFT_BYTEORDER_NTOH] = "ntoh",
 };