Make init_spin_delay() C89 compliant #2.

My previous attempt at doing so, in 80abbeba23, was not sufficient. While that
fixed the problem for bufmgr.c and lwlock.c , s_lock.c still has non-constant
expressions in the struct initializer, because the file/line/function
information comes from the caller of s_lock().

Give up on using a macro, and use a static inline instead.

Discussion: 4369.1460435533@sss.pgh.pa.us

src/backend/storage/buffer/bufmgr.c

@@ -4029,9 +4029,11 @@ rnode_comparator(const void *p1, const void *p2)
 uint32
 LockBufHdr(BufferDesc *desc)
 {
-	SpinDelayStatus delayStatus = init_local_spin_delay();
+	SpinDelayStatus delayStatus;
 	uint32		old_buf_state;
 
+	init_local_spin_delay(&delayStatus);
+
 	while (true)
 	{
 		/* set BM_LOCKED flag */
@@ -4055,9 +4057,11 @@ LockBufHdr(BufferDesc *desc)
 static uint32
 WaitBufHdrUnlocked(BufferDesc *buf)
 {
-	SpinDelayStatus delayStatus = init_local_spin_delay();
+	SpinDelayStatus delayStatus;
 	uint32		buf_state;
 
+	init_local_spin_delay(&delayStatus);
+
 	buf_state = pg_atomic_read_u32(&buf->state);
 
 	while (buf_state & BM_LOCKED)

src/backend/storage/lmgr/lwlock.c

@@ -870,7 +870,9 @@ LWLockWaitListLock(LWLock *lock)
 
 		/* and then spin without atomic operations until lock is released */
 		{
-			SpinDelayStatus delayStatus = init_local_spin_delay();
+			SpinDelayStatus delayStatus;
+
+			init_local_spin_delay(&delayStatus);
 
 			while (old_state & LW_FLAG_LOCKED)
 			{

src/backend/storage/lmgr/s_lock.c

@@ -91,7 +91,9 @@ s_lock_stuck(const char *file, int line, const char *func)
 int
 s_lock(volatile slock_t *lock, const char *file, int line, const char *func)
 {
-	SpinDelayStatus delayStatus = init_spin_delay(file, line, func);
+	SpinDelayStatus delayStatus;
+
+	init_spin_delay(&delayStatus, file, line, func);
 
 	while (TAS_SPIN(lock))
 	{

src/include/storage/s_lock.h

@@ -1005,8 +1005,19 @@ typedef struct
 	const char *func;
 } SpinDelayStatus;
 
-#define init_spin_delay(file, line, func) {0, 0, 0, file, line, func}
-#define init_local_spin_delay() init_spin_delay(__FILE__, __LINE__, PG_FUNCNAME_MACRO)
+static inline void
+init_spin_delay(SpinDelayStatus *status,
+				const char *file, int line, const char *func)
+{
+	status->spins = 0;
+	status->delays = 0;
+	status->cur_delay = 0;
+	status->file = file;
+	status->line = line;
+	status->func = func;
+}
+
+#define init_local_spin_delay(status) init_spin_delay(status, __FILE__, __LINE__, PG_FUNCNAME_MACRO)
 void perform_spin_delay(SpinDelayStatus *status);
 void finish_spin_delay(SpinDelayStatus *status);