On Wed, 18 May 2016, Ian Lepore wrote:
On Wed, 2016-05-18 at 22:02 +0000, Gleb Smirnoff wrote:
Log:
Revert r299830, it has couple of fatal errors.
The CMSG_ family of macros take care of alignment, so we don't need
r299830
at all, even if it was correct. Put NO_WCAST_ALIGN into Makefile.
The breaks detection of cast-align bugs elsewhere in the program.
So all of this was about a "cast increases required alignment" kind of
warning for a macro that takes care of alignment? Wouldn't the proper
fix then be to change CMSG_DATA() so that its internal cast is void*
instead of unsigned char* (he asked, knowing Bruce would come along
soon and point out why that's a dumb question)?
I don't know much about CMSG*, so I wouldn't have if you didn't ask :-).
Changing its type might expose bugs. Kernel code mostly casts it so
would get the same cast-align error if that were enabled in the kernel.
netinet6 passes it to a function without an explicit cast. The function
does an implicit conversion to a struct pointer and there should be a
different warning for that. char * and u_char * are required to be
binary compatible with void *, but it is bad style to depend on that.
So void * works better in all cases in the kernel.
LINUX_CMSG_DATA() already returns void *.
Bruce
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