Move extern declarations for EXEC_BACKEND to header files

This fixes warnings from -Wmissing-variable-declarations (not yet part
of the standard warning options) under EXEC_BACKEND.  The
NON_EXEC_STATIC variables need a suitable declaration in a header file
under EXEC_BACKEND.

Also fix the inconsistent application of the volatile qualifier for
PMSignalState, which was revealed by this change.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/e0a62134-83da-4ba4-8cdb-ceb0111c95ce@eisentraut.org

src/backend/postmaster/launch_backend.c

@@ -114,7 +114,7 @@ typedef struct
 	PROC_HDR   *ProcGlobal;
 	PGPROC	   *AuxiliaryProcs;
 	PGPROC	   *PreparedXactProcs;
-	PMSignalData *PMSignalState;
+	volatile PMSignalData *PMSignalState;
 	pid_t		PostmasterPid;
 	TimestampTz PgStartTime;
 	TimestampTz PgReloadTime;
@@ -668,16 +668,6 @@ SubPostmasterMain(int argc, char *argv[])
 	pg_unreachable();			/* main_fn never returns */
 }
 
-/*
- * The following need to be available to the save/restore_backend_variables
- * functions.  They are marked NON_EXEC_STATIC in their home modules.
- */
-extern slock_t *ProcStructLock;
-extern PGPROC *AuxiliaryProcs;
-extern PMSignalData *PMSignalState;
-extern pg_time_t first_syslogger_file_time;
-extern struct bkend *ShmemBackendArray;
-
 #ifndef WIN32
 #define write_inheritable_socket(dest, src, childpid) ((*(dest) = (src)), true)
 #define read_inheritable_socket(dest, src) (*(dest) = *(src))

src/include/postmaster/postmaster.h

@@ -36,6 +36,10 @@ extern PGDLLIMPORT bool remove_temp_files_after_crash;
 extern PGDLLIMPORT bool send_abort_for_crash;
 extern PGDLLIMPORT bool send_abort_for_kill;
 
+#ifdef EXEC_BACKEND
+extern struct bkend *ShmemBackendArray;
+#endif
+
 #ifdef WIN32
 extern PGDLLIMPORT HANDLE PostmasterHandle;
 #else

src/include/postmaster/syslogger.h

@@ -75,6 +75,10 @@ extern PGDLLIMPORT char *Log_filename;
 extern PGDLLIMPORT bool Log_truncate_on_rotation;
 extern PGDLLIMPORT int Log_file_mode;
 
+#ifdef EXEC_BACKEND
+extern pg_time_t first_syslogger_file_time;
+#endif
+
 #ifndef WIN32
 extern PGDLLIMPORT int syslogPipe[2];
 #else

src/include/storage/pmsignal.h

@@ -57,6 +57,10 @@ typedef enum
 /* PMSignalData is an opaque struct, details known only within pmsignal.c */
 typedef struct PMSignalData PMSignalData;
 
+#ifdef EXEC_BACKEND
+extern volatile PMSignalData *PMSignalState;
+#endif
+
 /*
  * prototypes for functions in pmsignal.c
  */

src/include/storage/proc.h

@@ -453,6 +453,11 @@ extern PGDLLIMPORT int TransactionTimeout;
 extern PGDLLIMPORT int IdleSessionTimeout;
 extern PGDLLIMPORT bool log_lock_waits;
 
+#ifdef EXEC_BACKEND
+extern slock_t *ProcStructLock;
+extern PGPROC *AuxiliaryProcs;
+#endif
+
 
 /*
  * Function Prototypes