Add nonnull and nullable attributes to API

This will warn if NULL is passed to any nonnull-annotated parameter, and is
also supported by sanitizers which can check for violations at runtime.

Unfortunately, it is currently only supported by clang.  GCC has a similar
feature in the nonnull attribute, but this has a different syntax (it's a
function attribute) and is more dangerous since it is used by the optimizer to
assume a null pointer is undefined behavior.  This one just warns and still
allows code to handle the situation gracefully, which I think is more
appropriate for a library API.

Note that this optimization behavior is not some unlikely edge case: switching
these attributes to the GCC one will break release builds.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/test_reader_writer.c b/test/test_reader_writer.c
index 60f8805f..41f57e77 100644
--- a/test/test_reader_writer.c
+++ b/test/test_reader_writer.c
@@ -286,7 +286,15 @@ test_reader(const char* path)
 	SerdNode g = serd_node_from_string(SERD_URI, USTR("http://example.org/"));
 	serd_reader_set_default_graph(reader, &g);
 	serd_reader_add_blank_prefix(reader, USTR("tmp"));
+
+#if defined(__GNUC__)
+#	pragma GCC diagnostic push
+#	pragma GCC diagnostic ignored "-Wnonnull"
+#endif
 	serd_reader_add_blank_prefix(reader, NULL);
+#if defined(__GNUC__)
+#	pragma GCC diagnostic pop
+#endif
 
 	assert(serd_reader_read_file(reader, USTR("http://notafile")));
 	assert(serd_reader_read_file(reader, USTR("file:///better/not/exist")));