diff options
| author | arehbein <arehbein@sysmocom.de> | 2023-09-16 22:41:22 +0200 |
|---|---|---|
| committer | arehbein <arehbein@sysmocom.de> | 2023-09-19 12:30:19 +0200 |
| commit | 35fcd6025d92c196e70a90c5bb7d85ead0b43f7a (patch) | |
| tree | 6e48763d6394fa1bc28c2c20c297d178de70928b | |
| parent | fd2eaea8246f8125cb526b0d2f248546fdbf1221 (diff) | |
ipa: Don't break strict aliasing rule
Somehow gcc doesn't always warn about this rule being broken.
We are breaking the strict aliasing rule here and libosmo-netif
currently does not make use of the '-fno-strict-aliasing' flag.
It's possible that this has also been causing nondeterministic
timestamps in libosmo-netif stream tests every once in a while.
Related: OS#6164, OS#5753
Change-Id: Ibed543cdfcdda8c0256ce7d8818ff96d6d46e9b0
| -rw-r--r-- | include/osmocom/netif/ipa.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/include/osmocom/netif/ipa.h b/include/osmocom/netif/ipa.h index 1923253..7826895 100644 --- a/include/osmocom/netif/ipa.h +++ b/include/osmocom/netif/ipa.h @@ -23,7 +23,19 @@ struct osmo_ipa_msgb_cb { uint8_t proto_ext; } __attribute__ ((packed)); -#define OSMO_IPA_MSGB_CB(__msg) ((struct osmo_ipa_msgb_cb *)&((__msg)->cb[0])) + +/* We don't just cast to 'struct osmo_ipa_msgb_cb *', because that would + * break the strict aliasing rule. Casting to a reference to a union with + * a compatible struct member seems to be allowed, though, see: + * N1570 Committee Draft — April 12, 2011 ISO/IEC 9899:201x, + * Section 6.5, §7 */ +#define OSMO_IPA_MSGB_CB(__msg) (&((( \ + union { \ + unsigned long cb; \ + struct osmo_ipa_msgb_cb _cb; \ + } \ + *)&((__msg)->cb[0]))->_cb)) + #define osmo_ipa_msgb_cb_proto(__x) OSMO_IPA_MSGB_CB(__x)->proto #define osmo_ipa_msgb_cb_proto_ext(__x) OSMO_IPA_MSGB_CB(__x)->proto_ext |