libnftables: Ensure output_fp is never NULL

Initialize output_fp to 'stdout' upon context creation and check output
stream validity in nft_ctx_set_output(). This allows to drop checks in
nft_{gmp_,}print() and do_command_export(). While doing so for the
latter, simplify it a bit by using nft_print() which takes care of
flushing the output stream.

If applications desire to drop all output, they are supposed to open
/dev/null and assign that.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 0 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index ff7878c9..353b87bc 100644
--- a/src/main.c
+++ b/src/main.c
@@ -173,7 +173,6 @@ int main(int argc, char * const *argv)
 	int i, val, rc;
 
 	nft = nft_ctx_new(NFT_CTX_DEFAULT);
-	nft_ctx_set_output(nft, stdout);
 
 	while (1) {
 		val = getopt_long(argc, argv, OPTSTRING, options, NULL);