svn commit: r286103 - head/share/man/man9

[Bruce Evans]

On Tue, 4 Aug 2015, Ed Schouten wrote:

> 2015-08-04 20:23 GMT+02:00 Warner Losh <imp at bsdimp.com>:
>> There’s at least one compiler in common use that warns about
>>
>> extern int fred[1];
>> extern int fred[1];
>>
>> being a repeated declaration (despite being legal C).
>
> Would you happen to know which one that is?

All non-broken compilers warn about this when directed to do so by
-Wredundant-decls.  I think -Wno-system-headers turns this off, but
we use -Wsystem-headers so as to see bugs in our system headers.

clang is broken and doesn't even warn that it ignores -Wredundant-decls.

We use -Wredundant-decls at WARNS >= 6.  We used to use it always in the
kernel, but now we turn it and most other warnings off in cddl code.

We use -Wsystem-headers at WARNS >= 1.  We don't use it explicitly in
the kernel.  That might be a bug.  The kernel uses nonstandard include
paths, but so does userland for bootstrapping and cross compiling.
The kernel also uses -nostdinc and that should kill any idea that the
kernel has about which headers are system ones.  Makeworld doesn't
seem to use -nostdinc.  That might be another bug.  It uses lots of
-I paths, but there is still a possibility of getting host headers
mixed with target ones.  cddl has different messes for -nostdinc.  It
seems to duplicate it together with spamming CFLAGS with lots of -I's.

Bruce