On Mon, 10 Jun 2019, Ian Lepore wrote:
On Mon, 2019-06-10 at 07:49 -0600, Warner Losh wrote:
On Mon, Jun 10, 2019, 7:44 AM Conrad Meyer <c...@freebsd.org> wrote:
On Mon, Jun 10, 2019 at 2:10 AM T??l Coosemans <t...@freebsd.org>
wrote:
On Mon, 10 Jun 2019 05:28:04 +0000 (UTC) Dmitry Chagin
<dcha...@freebsd.org> wrote:
...
URL: https://svnweb.freebsd.org/changeset/base/348847
Log:
Use C11 anonymous unions.
Modified: head/sys/sys/ucred.h
...
Isn't this a userland header that should work with non-C11
compilers?
...
Why would one expect userland headers to work with non-C11 (gnu89)
compilers?
...
Because those compilers can choose non c11 variants of the language?
Do we promise that userland will compile with -std=c89? I hope not.
Only headers and libraries should support -std=c89. <sys/cdefs.h> has
lots of support for compilers and POSIX versions going back to K&R C,
and only the K&R parts are completely broken.
FreeBSD also has the c89 and c99 utilities. These require c89 and c99
headers to work under FreeBSD. c89 uses CFLAGS -std=iso9899:199409
-pedantic. I don't see how a 1994 standard can be correct for c89,
but -pedantic here might avoid the bug that -std=cxx doesn't actually
gives standard cxx, especially for clang. c99 uses -std=iso9899:1999
-pedantic. So anonymous unions are correctly disallowed by both c89
and c99.
At least the following headers still compile with c89: sys/types.h,
stdio.h, stdlib.h, the old version of sys/ucred.h.
Anonymous unions may be a c11 feature, but they're also available with
-std=gnu99, which I think is how we compile userland.
That is only the default, only for for parts of userland controlled by us.
Non-FreeBSD makefiles get at most the POSIX CFLAGS (something like -O)
from sys.mk if they use FreeBSD make, and something similar using gmake.
I think -std=gnu99 is how we should also compile the kernel, and I
think Bruce has been trying to say that for several years (but I'm not
sure, because the emails that seem to say so are always so full of
semi-related extraneous material that it's hard to be sure what they're
saying).
-std can be forced for kernel builds and other pure FreeBSD builds, but
then it should be the correct one.
bsd.sys.mk only directly supports the user selecting the following standards:
- c89 or c90
- c94 or c95 (the c89 utility gives -std=c94, not -std=c89)
- c99
- gnu99 (default)
Newer and more useful old standards like gnu89 are hard to select. The
user must set the undocumented variable CSTD even to change the default to
c89/90/94/95. Adding -std=whatever to CFLAGS only works if it happens to
be added after -std=${CSTD}.
Bruce_______________________________________________
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