hurd: Add shared mig declarations

We are using -Werror=missing-declarations, and the _S.h files generated
by mig do not currently include a declaration for the server routine.
gnu-nat.c used to have its own external declarations, but better just
share them between gnu-nat.c and the _S.c files.

Fixes

exc_request_S.c:177:24: error: no previous declaration for ‘exc_server’ [-Werror=missing-declarations]
  177 | mig_external boolean_t exc_server

gdb/ChangeLog:

	* config/i386/i386gnu.mn [%_S.o %_U.o] (COMPILE.post): Add
	"-include gnu-nat-mig.h".
	* gnu-nat-mig.h: New file.
	* gnu-nat.c: Include "gnu-nat-mig.h".
	(exc_server, msg_reply_server, notify_server,
	process_reply_server): Remove declarations.

4 files changed, 43 insertions, 7 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a974b43..c95c168 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2020-06-01  Samuel Thibault  <samuel.thibault@ens-lyon.org>
+
+	* config/i386/i386gnu.mn [%_S.o %_U.o] (COMPILE.post): Add
+	"-include gnu-nat-mig.h".
+	* gnu-nat-mig.h: New file.
+	* gnu-nat.c: Include "gnu-nat-mig.h".
+	(exc_server, msg_reply_server, notify_server,
+	process_reply_server): Remove declarations.
+
 2020-05-30  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* gnu-nat.h (inf_validate_procs, inf_suspend, inf_set_traced,
diff --git a/gdb/config/i386/i386gnu.mn b/gdb/config/i386/i386gnu.mn
index b1985b7..b7414e3 100644
--- a/gdb/config/i386/i386gnu.mn
+++ b/gdb/config/i386/i386gnu.mn
@@ -21,7 +21,7 @@ MIGCOM = $(MIG) -cc cat - /dev/null
 	| $(MIGCOM) -sheader /dev/null -server /dev/null -user $*_U.c -header $*_U.h
 
 # MIG stubs are not yet ready for C++ compilation.
-%_S.o %_U.o : COMPILE.post += -x c
+%_S.o %_U.o : COMPILE.post += -x c -include gnu-nat-mig.h
 
 NAT_GENERATED_FILES = notify_S.h notify_S.c \
 	process_reply_S.h process_reply_S.c \
diff --git a/gdb/gnu-nat-mig.h b/gdb/gnu-nat-mig.h
new file mode 100644
index 0000000..4cceff1
--- /dev/null
+++ b/gdb/gnu-nat-mig.h
@@ -0,0 +1,31 @@
+/* Common things used by the various *gnu-nat.c files
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GNU_NAT_MIG_H
+#define GNU_NAT_MIG_H
+
+#include <mach/boolean.h>
+#include <mach/message.h>
+
+boolean_t exc_server (mach_msg_header_t *InHeadP, mach_msg_header_t *OutHeadP);
+boolean_t msg_reply_server (mach_msg_header_t *InHeadP,
+			    mach_msg_header_t *OutHeadP);
+boolean_t notify_server (mach_msg_header_t *InHeadP,
+			 mach_msg_header_t *OutHeadP);
+boolean_t process_reply_server (mach_msg_header_t *InHeadP,
+				mach_msg_header_t *OutHeadP);
+
+#endif /* GNU_NAT_MIG_H */
diff --git a/gdb/gnu-nat.c b/gdb/gnu-nat.c
index bb277da..44adda5 100644
--- a/gdb/gnu-nat.c
+++ b/gdb/gnu-nat.c
@@ -83,6 +83,8 @@ extern "C"
 #include "msg_reply_S.h"
 #include "exc_request_U.h"
 #include "msg_U.h"
+
+#include "gnu-nat-mig.h"
 }
 
 struct gnu_nat_target *gnu_target;
@@ -1430,12 +1432,6 @@ struct inf *gnu_current_inf = 0;
    multi-threaded, we don't bother to lock this.  */
 static struct inf *waiting_inf;
 
-/* MIG stubs are not yet ready for C++ compilation.  */
-extern "C" int exc_server (mach_msg_header_t *, mach_msg_header_t *);
-extern "C" int msg_reply_server (mach_msg_header_t *, mach_msg_header_t *);
-extern "C" int notify_server (mach_msg_header_t *, mach_msg_header_t *);
-extern "C" int process_reply_server (mach_msg_header_t *, mach_msg_header_t *);
-
 /* Wait for something to happen in the inferior, returning what in STATUS.  */
 
 ptid_t