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[PATCH] -Wredundant-decls, do not warn for static forward decl
- From: Craig Rodrigues <rodrigc at crodrigues dot org>
- To: gcc-patches at gcc dot gnu dot org
- Date: Sat, 27 Aug 2005 20:16:15 -0400
- Subject: [PATCH] -Wredundant-decls, do not warn for static forward decl
Hi,
The FreeBSD kernel has code such as this which compiles with
gcc 3.4:
extern struct domain routedomain; /* or at least forward */
static struct protosw routesw[] = {
{ SOCK_RAW, &routedomain, 0, PR_ATOMIC|PR_ADDR,
0, route_output, raw_ctlinput, 0,
0,
raw_init, 0, 0, 0,
&route_usrreqs
}
};
static struct domain routedomain =
{ PF_ROUTE, "route", 0, 0, 0,
routesw, &routesw[sizeof(routesw)/sizeof(routesw[0])] };
This of course is illegal ISO C, and gcc 4.0 will correctly
issue an error message:
error: static declaration of 'routedomain' follows non-static declaration
Changing this could to be:
static struct domain routedomain; /* or at least forward */
will compile without error, but will emit a warning
with -Wredundant-decls:
warning: redundant redeclaration of 'routedomain'
I had a discussion on the freebsd-arch mailing list with the
FreeBSD developers on how to fix this problem:
http://lists.freebsd.org/pipermail/freebsd-arch/2005-August/004181.html
Basically, the result of the discussion was that
code which is illegal ISO C should be fixed, but it would be
nice to fix GCC so that -Wredundant-decls does not warn for static forward
declarations. -Wredundant-decls in other cases emits useful warnings,
but in this case, the warning is not useful.
Would the following patch to c-decl.c be acceptable?
2005-8-27 Craig Rodrigues <rodrigc@gcc.gnu.org>
* c-decl.c (diagnose_mismatched_decls): With -Wredundant-decls,
do not issue warning for static forward declaration of static variables.
Index: c-decl.c
===================================================================
RCS file: /cvsroot/gcc/gcc/gcc/c-decl.c,v
retrieving revision 1.630.6.16
diff -u -u -r1.630.6.16 c-decl.c
--- c-decl.c 16 Aug 2005 20:34:19 -0000 1.630.6.16
+++ c-decl.c 27 Aug 2005 23:43:06 -0000
@@ -1559,7 +1559,10 @@
&& !(DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl))
/* Don't warn about forward parameter decls. */
&& !(TREE_CODE (newdecl) == PARM_DECL
- && TREE_ASM_WRITTEN (olddecl) && !TREE_ASM_WRITTEN (newdecl)))
+ && TREE_ASM_WRITTEN (olddecl) && !TREE_ASM_WRITTEN (newdecl))
+ /* Don't warn about forward static variable decls. */
+ && !(TREE_CODE (newdecl) == VAR_DECL
+ && !TREE_PUBLIC (olddecl) && !TREE_PUBLIC (newdecl)))
{
warning ("%Jredundant redeclaration of %qD", newdecl, newdecl);
warned = true;
--
Craig Rodrigues
rodrigc@crodrigues.org