On Thu, Apr 14, 2016 at 09:33:37AM -0400, Holger Freyther wrote:

...

On 14 Apr 2016, at 08:49, Neels Hofmeyr nhofmeyr@sysmocom.de wrote:

This is after the patch to libasn1c, removing str arg constness.

src/ranap_msg_factory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ranap_msg_factory.c b/src/ranap_msg_factory.c index bdae92e..461df1a 100644 --- a/src/ranap_msg_factory.c +++ b/src/ranap_msg_factory.c @@ -181,7 +181,7 @@ struct msgb *ranap_new_msg_dt(uint8_t sapi, const uint8_t *nas, unsigned int nas ies.sapi = RANAP_SAPI_sapi_0;

/* Avoid copying + later freeing of OCTET STRING */

• OCTET_STRING_noalloc(&ies.nas_pdu, nas, nas_len);

• OCTET_STRING_noalloc(&ies.nas_pdu, (uint8_t*)nas, nas_len);

doesn't seem the right way forward. Does OCTET_STRING_noalloc or its users need/want to modify the buffer?

So, I want to change this:

static inline void OCTET_STRING_noalloc(OCTET_STRING_t *s, const uint8_t *str, int size) { s->buf = str; s->size = size; }

because OCTET_STRING_t.s is not const, and must not be const, will never be const. OCTET_STRING_noalloc() has no way to tell whether callers will subsequently modify the buffer or not. So that function must not secretly unconst:

static inline void OCTET_STRING_noalloc(OCTET_STRING_t *s, const uint8_t *str, int size) { s->buf = (uint8_t*)str; s->size = size; }

^ this is bad.

To get rid of compiler warnings, I want to change to more sensible:

static inline void OCTET_STRING_noalloc(OCTET_STRING_t *s, uint8_t *str, int size) { s->buf = str; s->size = size; }

All callers of OCTET_STRING_noalloc() pass a non-const pointer, except that one above. I just want to unconst that single caller.

OCTET_STRING_t.buf is simply not const. So if we're not going to do an ugly unconst like this somewhere, we have to change ranap_new_msg_dt() to take a non-const uint8_t* nas. I didn't want to change that though, because the function does rightfully signal outwards that *nas is never changed, because its use of the unconsted value is contained entirely in that function (to encode a message) and nas is in fact not modified (given that the encoders work correctly).

Admitted, I should also add a comment.

~Neels