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Incomplete patch to fix build with top-of-tree GCC

From: Steve Ellcey <sellcey at imgtec dot com>
To: GNU C Library <libc-alpha at sourceware dot org>
Date: Fri, 15 May 2015 09:42:50 -0700
Subject: Incomplete patch to fix build with top-of-tree GCC
Authentication-results: sourceware.org; auth=none
Reply-to: <sellcey at imgtec dot com>

I was wondering if anyone can help me with a patch to fix the glibc
build with the latest GCC.  A recent GCC patch to fix middle-end/66110
caused us to get some new strict-aliasing errors.  I can do the
mechanical change to use the DIAG_* macros to allow the
non-strict-aliasing but the macros need to be accompanied by a comment
about why it is OK to ignore the warnings and I am not sure how to write
a coherent explanation of that since I am not familiar with the code in
question.  Here is the patch I have so far with no comments, does any
one want to help finish it by adding some comments?

Steve Ellcey
sellcey@imgtec.com



2015-05-15  Steve Ellcey  <sellcey@imgtec.com>

	* inet/rcmd.c (__ivaliduser): Ignore strict-aliasing.
	(iruserok_af): Ditto.
	* libio/memstream.c (open_memstream): Ditto.
	* libio/oldiofdopen.c (_IO_old_fdopen): Ditto.
	* libio/oldiofopen.c (_IO_old_fopen): Ditto.
	* libio/oldiopopen.c (_IO_old_popen): Ditto.
	* resolv/res_hconf.c (_res_hconf_reorder_addrs): Ditto.

diff --git a/inet/rcmd.c b/inet/rcmd.c
index acacaa0..f2c04b7 100644
--- a/inet/rcmd.c
+++ b/inet/rcmd.c
@@ -82,6 +82,7 @@ static char sccsid[] = "@(#)rcmd.c	8.3 (Berkeley) 3/26/94";
 #include <stdlib.h>
 #include <wchar.h>
 #include <sys/uio.h>
+#include <libc-internal.h>
 
 
 int __ivaliduser (FILE *, u_int32_t, const char *, const char *);
@@ -382,11 +383,17 @@ rresvport_af(alport, family)
 	switch(family){
 	case AF_INET:
 		len = sizeof(struct sockaddr_in);
+		DIAG_PUSH_NEEDS_COMMENT;
+		DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
 		sport = &((struct sockaddr_in *)&ss)->sin_port;
+		DIAG_POP_NEEDS_COMMENT;
 		break;
 	case AF_INET6:
 		len = sizeof(struct sockaddr_in6);
+		DIAG_PUSH_NEEDS_COMMENT;
+		DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
 		sport = &((struct sockaddr_in6 *)&ss)->sin6_port;
+		DIAG_POP_NEEDS_COMMENT;
 		break;
 	default:
 		__set_errno (EAFNOSUPPORT);
@@ -611,14 +618,20 @@ iruserok_af (raddr, superuser, ruser, luser, af)
   switch (af){
   case AF_INET:
     ra.ss_family = AF_INET;
+    DIAG_PUSH_NEEDS_COMMENT;
+    DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
     memcpy (&(((struct sockaddr_in *)&ra)->sin_addr), raddr,
 	    sizeof(struct in_addr));
+    DIAG_POP_NEEDS_COMMENT;
     ralen = sizeof(struct sockaddr_in);
     break;
   case AF_INET6:
     ra.ss_family = AF_INET6;
+    DIAG_PUSH_NEEDS_COMMENT;
+    DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
     memcpy (&(((struct sockaddr_in6 *)&ra)->sin6_addr), raddr,
 	    sizeof(struct in6_addr));
+    DIAG_POP_NEEDS_COMMENT;
     ralen = sizeof(struct sockaddr_in6);
     break;
   default:
diff --git a/libio/memstream.c b/libio/memstream.c
index e1c5434..b6abf6f 100644
--- a/libio/memstream.c
+++ b/libio/memstream.c
@@ -19,6 +19,7 @@
 #include "strfile.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <libc-internal.h>
 
 
 struct _IO_FILE_memstream
@@ -89,7 +90,10 @@ open_memstream (bufloc, sizeloc)
       return NULL;
     }
   _IO_init (&new_f->fp._sf._sbf._f, 0);
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
   _IO_JUMPS ((struct _IO_FILE_plus *) &new_f->fp._sf._sbf) = &_IO_mem_jumps;
+  DIAG_POP_NEEDS_COMMENT;
   _IO_str_init_static_internal (&new_f->fp._sf, buf, _IO_BUFSIZ, buf);
   new_f->fp._sf._sbf._f._flags &= ~_IO_USER_BUF;
   new_f->fp._sf._s._allocate_buffer = (_IO_alloc_type) malloc;
diff --git a/libio/oldiofdopen.c b/libio/oldiofdopen.c
index e0d5354..56520f6 100644
--- a/libio/oldiofdopen.c
+++ b/libio/oldiofdopen.c
@@ -31,6 +31,7 @@
 #include <stdlib.h>
 #include "libioP.h"
 #include <fcntl.h>
+#include <libc-internal.h>
 
 #ifndef _IO_fcntl
 # define _IO_fcntl __fcntl
@@ -113,7 +114,10 @@ _IO_old_fdopen (fd, mode)
   new_f->fp.file._file._lock = &new_f->lock;
 #endif
   _IO_old_init (&new_f->fp.file._file, 0);
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
   _IO_JUMPS ((struct _IO_FILE_plus *) &new_f->fp) = &_IO_old_file_jumps;
+  DIAG_POP_NEEDS_COMMENT;
   _IO_old_file_init ((struct _IO_FILE_plus *) &new_f->fp);
 #if  !_IO_UNIFIED_JUMPTABLES
   new_f->fp.vtable = NULL;
diff --git a/libio/oldiofopen.c b/libio/oldiofopen.c
index dac424a..be6df8f 100644
--- a/libio/oldiofopen.c
+++ b/libio/oldiofopen.c
@@ -30,6 +30,7 @@
 #define _IO_USE_OLD_IO_FILE
 #include "libioP.h"
 #include <stdlib.h>
+#include <libc-internal.h>
 
 
 _IO_FILE *
@@ -52,7 +53,10 @@ _IO_old_fopen (filename, mode)
   new_f->fp.file._file._lock = &new_f->lock;
 #endif
   _IO_old_init (&new_f->fp.file._file, 0);
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
   _IO_JUMPS ((struct _IO_FILE_plus *) &new_f->fp) = &_IO_old_file_jumps;
+  DIAG_POP_NEEDS_COMMENT;
   _IO_old_file_init ((struct _IO_FILE_plus *) &new_f->fp);
 #if  !_IO_UNIFIED_JUMPTABLES
   new_f->fp.vtable = NULL;
diff --git a/libio/oldiopopen.c b/libio/oldiopopen.c
index f6bcf5d..e89c761 100644
--- a/libio/oldiopopen.c
+++ b/libio/oldiopopen.c
@@ -38,6 +38,7 @@
 #endif
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <libc-internal.h>
 
 #ifndef _IO_fork
 #ifdef _LIBC
@@ -215,7 +216,10 @@ _IO_old_popen (command, mode)
 #endif
   fp = &new_f->fpx.file.file._file;
   _IO_old_init (fp, 0);
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
   _IO_JUMPS ((struct _IO_FILE_plus *) &new_f->fpx.file) = &_IO_old_proc_jumps;
+  DIAG_POP_NEEDS_COMMENT;
   _IO_old_file_init ((struct _IO_FILE_plus *) &new_f->fpx.file);
 #if  !_IO_UNIFIED_JUMPTABLES
   new_f->fpx.file.vtable = NULL;
diff --git a/resolv/res_hconf.c b/resolv/res_hconf.c
index 73942e8..7ce819f 100644
--- a/resolv/res_hconf.c
+++ b/resolv/res_hconf.c
@@ -45,6 +45,7 @@
 #include "ifreq.h"
 #include "res_hconf.h"
 #include <wchar.h>
+#include <libc-internal.h>
 
 #if IS_IN (libc)
 # define fgets_unlocked __fgets_unlocked
@@ -443,14 +444,20 @@ _res_hconf_reorder_addrs (struct hostent *hp)
 		continue;
 
 	      ifaddrs[new_num_ifs].addrtype = AF_INET;
+	      DIAG_PUSH_NEEDS_COMMENT;
+	      DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
 	      ifaddrs[new_num_ifs].u.ipv4.addr =
 		((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
+	      DIAG_POP_NEEDS_COMMENT;
 
 	      if (__ioctl (sd, SIOCGIFNETMASK, cur_ifr) < 0)
 		continue;
 
+	      DIAG_PUSH_NEEDS_COMMENT;
+	      DIAG_IGNORE_NEEDS_COMMENT (5, "-Wstrict-aliasing");
 	      ifaddrs[new_num_ifs].u.ipv4.mask =
 		((struct sockaddr_in *) &cur_ifr->ifr_netmask)->sin_addr.s_addr;
+	      DIAG_POP_NEEDS_COMMENT;
 
 	      /* Now we're committed to this entry.  */
 	      ++new_num_ifs;

Follow-Ups:
- Re: Incomplete patch to fix build with top-of-tree GCC
  - From: Joseph Myers

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