Replace pgwin32_is_junction() with lstat().

Now that lstat() reports junction points with S_IFLNK/S_ISLINK(), and
unlink() can unlink them, there is no need for conditional code for
Windows in a few places.  That was expressed by testing for WIN32 or
S_ISLNK, which we can now constant-fold.

The coding around pgwin32_is_junction() was a bit suspect anyway, as we
never checked for errors, and we also know that errors can be spuriously
reported because of transient sharing violations on this OS.  The
lstat()-based code has handling for that.

This also reverts 4fc6b6ee on master only.  That was done because
lstat() didn't previously work for symlinks (junction points), but now
it does.

Tested-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
(cherry picked from commit 5fc88c5d53e43fa7dcea93499d230a0bf70f4f77)

Author: Thomas Munro <tmunro@postgresql.org>
Author: Alexandra Wang <alexandra.wang.oss@gmail.com>

1 files changed, 0 insertions, 23 deletions

diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 966b987d648..df4d6d240c0 100644
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -79,7 +79,6 @@ fsync_pgdata(const char *pg_data,
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -88,10 +87,6 @@ fsync_pgdata(const char *pg_data,
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction(pg_wal))
-		xlog_is_symlink = true;
-#endif
 
 	/*
 	 * If possible, hint to the kernel that we're soon going to fsync the data
@@ -459,27 +454,9 @@ get_dirent_type(const char *path,
 			result = PGFILETYPE_REG;
 		else if (S_ISDIR(fst.st_mode))
 			result = PGFILETYPE_DIR;
-#ifdef S_ISLNK
 		else if (S_ISLNK(fst.st_mode))
 			result = PGFILETYPE_LNK;
-#endif
 	}
 
-#if defined(WIN32) && !defined(_MSC_VER)
-
-	/*
-	 * If we're on native Windows (not Cygwin, which has its own POSIX
-	 * symlinks), but not using the MSVC compiler, then we're using a
-	 * readdir() emulation provided by the MinGW runtime that has no d_type.
-	 * Since the lstat() fallback code reports junction points as directories,
-	 * we need an extra system call to check if we should report them as
-	 * symlinks instead, following our convention.
-	 */
-	if (result == PGFILETYPE_DIR &&
-		!look_through_symlinks &&
-		pgwin32_is_junction(path))
-		result = PGFILETYPE_LNK;
-#endif
-
 	return result;
 }