Checking pgwin32_is_junction() errors

From ec732571a1fa88fefcf9834987114716eb9c5998 Mon Sep 17 00:00:00 2001
From: Melih Mutlu <memutlu@microsoft.com>
Date: Mon, 21 Feb 2022 14:46:05 +0300
Subject: [PATCH 1/3] Added Windows with MinGW environment in Cirrus CI

---
 .cirrus.yml | 79 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 65 insertions(+), 14 deletions(-)

diff --git a/.cirrus.yml b/.cirrus.yml
index f23d6cae55..3d8c4cd813 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -23,7 +23,6 @@ env:
   CHECKFLAGS: -Otarget
   PROVE_FLAGS: --timer
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
-  TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
   PG_TEST_EXTRA: kerberos ldap ssl
 
 
@@ -338,13 +337,30 @@ task:
     cores_script: src/tools/ci/cores_backtrace.sh macos "${HOME}/cores"
 
 
+WINDOWS_ENVIRONMENT_BASE: &WINDOWS_ENVIRONMENT_BASE
+    env:
+      # Half the allowed per-user CPU cores
+      CPUS: 4
+      # The default working dir is in a directory msbuild complains about
+      CIRRUS_WORKING_DIR: "c:/cirrus"
+      TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
+
+      # Avoids port conflicts between concurrent tap test runs
+      PG_TEST_USE_UNIX_SOCKETS: 1
+
+    only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*windows.*'
+
+    sysinfo_script: |
+      chcp
+      systeminfo
+      powershell -Command get-psdrive -psprovider filesystem
+      set
+
 task:
+  << : *WINDOWS_ENVIRONMENT_BASE
   name: Windows - Server 2019, VS 2019
 
   env:
-    # Half the allowed per-user CPU cores
-    CPUS: 4
-
     # Our windows infrastructure doesn't have test concurrency above the level
     # of a single vcregress test target. Due to that, it's useful to run prove
     # with multiple jobs. For the other tasks it isn't, because two sources
@@ -354,15 +370,11 @@ task:
     # likely can be improved upon further.
     PROVE_FLAGS: -j10 --timer
 
-    # The default cirrus working dir is in a directory msbuild complains about
-    CIRRUS_WORKING_DIR: "c:/cirrus"
     # Avoid re-installing over and over
     NO_TEMP_INSTALL: 1
     # git's tar doesn't deal with drive letters, see
     # https://postgr.es/m/b6782dc3-a7b0-ed56-175f-f8f54cb08d67%40dunslane.net
     TAR: "c:/windows/system32/tar.exe"
-    # Avoids port conflicts between concurrent tap test runs
-    PG_TEST_USE_UNIX_SOCKETS: 1
     PG_REGRESS_SOCK_DIR: "c:/cirrus/"
     # -m enables parallelism
     # verbosity:minimal + Summary reduce verbosity, while keeping a summary of
@@ -393,12 +405,6 @@ task:
     cpu: $CPUS
     memory: 4G
 
-  sysinfo_script: |
-    chcp
-    systeminfo
-    powershell -Command get-psdrive -psprovider filesystem
-    set
-
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
@@ -456,6 +462,51 @@ task:
       path: "crashlog-*.txt"
       type: text/plain
 
+task:
+  << : *WINDOWS_ENVIRONMENT_BASE
+  name: Windows - Server 2019, MinGW64
+  windows_container:
+    image: $CONTAINER_REPO/windows_ci_mingw64:latest
+    cpu: $CPUS
+    memory: 4G
+  env:
+    CCACHE_DIR: C:/msys64/ccache
+    BUILD_DIR: "%CIRRUS_WORKING_DIR%/build"
+
+  ccache_cache:
+    folder: ${CCACHE_DIR}
+
+  mingw_info_script:
+    - C:\msys64\usr\bin\bash.exe -lc "where gcc"
+    - C:\msys64\usr\bin\bash.exe -lc "gcc --version"
+    - C:\msys64\usr\bin\bash.exe -lc "where perl"
+    - C:\msys64\usr\bin\bash.exe -lc "perl --version"
+
+  configure_script:
+    - C:\msys64\usr\bin\bash.exe -lc "mkdir %BUILD_DIR% &&
+      cd %BUILD_DIR% &&
+      %CIRRUS_WORKING_DIR%/configure
+        --host=x86_64-w64-mingw32
+        --enable-cassert
+        --enable-tap-tests
+        --with-icu
+        --with-libxml
+        --with-libxslt
+        --with-lz4
+        --enable-debug
+        CC='ccache gcc'
+        CXX='ccache g++'"
+
+  build_script:
+    C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s world-bin -j${CPUS}"
+
+  upload_caches: ccache
+
+  tests_script:
+  - set "NoDefaultCurrentDirectoryInExePath=0"
+  - C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s ${CHECK} ${CHECKFLAGS} -j${CPUS} TMPDIR=%BUILD_DIR%/tmp_install"
+
+  on_failure: *on_failure
 
 task:
   name: CompilerWarnings
-- 
2.36.1

From 2390efc8ffebcb975c0c96b63479a1f22bf8e422 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 28 Jul 2022 15:19:38 +1200
Subject: [PATCH 2/3] Provide lstat() for Windows.

Junction points will be reported with S_ISLNK(x.st_mode), like in POSIX.
stat() will follow symlinks, like in POSIX (but only one level before it
gives up, unlike in POSIX).

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/include/port/win32_port.h | 18 +++++++-
 src/port/win32stat.c          | 79 +++++++++++++++++++++++++++++++++--
 2 files changed, 92 insertions(+), 5 deletions(-)

diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index 4de5bf3bf6..b8cf2e1480 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -286,10 +286,11 @@ struct stat						/* This should match struct __stat64 */
 
 extern int	_pgfstat64(int fileno, struct stat *buf);
 extern int	_pgstat64(const char *name, struct stat *buf);
+extern int	_pglstat64(const char *name, struct stat *buf);
 
 #define fstat(fileno, sb)	_pgfstat64(fileno, sb)
 #define stat(path, sb)		_pgstat64(path, sb)
-#define lstat(path, sb)		_pgstat64(path, sb)
+#define lstat(path, sb)		_pglstat64(path, sb)
 
 /* These macros are not provided by older MinGW, nor by MSVC */
 #ifndef S_IRUSR
@@ -335,6 +336,21 @@ extern int	_pgstat64(const char *name, struct stat *buf);
 #define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
 #endif
 
+/*
+ * In order for lstat() to be able to report junction points as symlinks, we
+ * need to hijack a bit in st_mode, since neither MSVC nor MinGW provides
+ * S_ISLNK and there aren't any spare bits.  We'll steal the one for character
+ * devices, because we don't otherwise make use of those.
+ */
+#ifdef S_ISLNK
+#error "S_ISLNK is already defined"
+#endif
+#ifdef S_IFLNK
+#error "S_IFLNK is already defined"
+#endif
+#define S_IFLNK S_IFCHR
+#define S_ISLNK(m) (((m) & S_IFLNK) == S_IFLNK)
+
 /*
  * Supplement to <fcntl.h>.
  * This is the same value as _O_NOINHERIT in the MS header file. This is
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index e03ed5f35c..686c510fed 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -15,7 +15,11 @@
 
 #ifdef WIN32
 
+#define UMDF_USING_NTSTATUS
+
 #include "c.h"
+#include "port/win32ntdll.h"
+
 #include <windows.h>
 
 /*
@@ -107,12 +111,10 @@ fileinfo_to_stat(HANDLE hFile, struct stat *buf)
 }
 
 /*
- * Windows implementation of stat().
- *
- * This currently also implements lstat(), though perhaps that should change.
+ * Windows implementation of lstat().
  */
 int
-_pgstat64(const char *name, struct stat *buf)
+_pglstat64(const char *name, struct stat *buf)
 {
 	/*
 	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
@@ -129,10 +131,79 @@ _pgstat64(const char *name, struct stat *buf)
 
 	ret = fileinfo_to_stat(hFile, buf);
 
+	/*
+	 * Unfortunately it's not possible for fileinfo_to_stat() to see a
+	 * FILE_ATTRIBUTE_REPARSE_POINT flag with just a handle, so at this point
+	 * junction points appear as directories.  Ask for the full attributes
+	 * while we still have the handle open.  Someone else can unlink the file
+	 * while we have it open, but they can't create another file with the same
+	 * name.
+	 */
+	if (ret == 0 && S_ISDIR(buf->st_mode))
+	{
+		DWORD		attr;
+
+		attr = GetFileAttributes(name);
+		if (attr == INVALID_FILE_ATTRIBUTES)
+		{
+			DWORD		err;
+
+			/* If it's been unlinked since we opened it, report as ENOENT. */
+			err = GetLastError();
+			if (err == ERROR_ACCESS_DENIED &&
+				pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
+				errno = ENOENT;
+			else
+				_dosmaperr(err);
+
+			ret = -1;
+		}
+		else if (attr & FILE_ATTRIBUTE_REPARSE_POINT)
+		{
+			buf->st_mode &= ~S_IFDIR;
+			buf->st_mode |= S_IFLNK;
+		}
+	}
+
 	CloseHandle(hFile);
 	return ret;
 }
 
+/*
+ * Windows implementation of stat().
+ */
+int
+_pgstat64(const char *name, struct stat *buf)
+{
+	int			ret;
+
+	ret = _pglstat64(name, buf);
+
+	/* Do we need to follow a symlink (junction point)? */
+	if (ret == 0 && S_ISLNK(buf->st_mode))
+	{
+		char		next[MAXPGPATH];
+
+		if (readlink(name, next, sizeof(next)) < 0)
+			return -1;
+
+		ret = _pglstat64(next, buf);
+		if (ret == 0 && S_ISLNK(buf->st_mode))
+		{
+			/*
+			 * We're only prepared to go one hop, because we only expect to
+			 * deal with the simple cases that we create.  The error for too
+			 * many symlinks is supposed to be ELOOP, but Windows hasn't got
+			 * it.
+			 */
+			errno = EIO;
+			return -1;
+		}
+	}
+
+	return ret;
+}
+
 /*
  * Windows implementation of fstat().
  */
-- 
2.36.1

From 2d44c134f62872889439db6910709af745901dd9 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 28 Jul 2022 15:25:10 +1200
Subject: [PATCH 3/3] Remove pgwin32_is_junction().

Now that lstat() reports junction points with S_IFLNK, there is no need
for sparate code paths for Windows in a few places.  The coding around
pgwin32_is_junction() was a bit suspect anyway, as we never checked for
errors.

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/backend/commands/tablespace.c    |  3 +--
 src/backend/replication/basebackup.c | 12 +-----------
 src/backend/storage/file/fd.c        |  5 -----
 src/backend/utils/adt/misc.c         |  7 -------
 src/bin/pg_checksums/pg_checksums.c  |  4 ----
 src/bin/pg_rewind/file_ops.c         |  4 ----
 src/common/file_utils.c              | 21 --------------------
 src/include/port.h                   |  1 -
 src/include/port/win32_port.h        |  1 -
 src/port/dirmod.c                    | 29 +++++++++++++---------------
 10 files changed, 15 insertions(+), 72 deletions(-)

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index cb7d46089a..b74f40aac6 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -827,8 +827,7 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
 	/*
 	 * Try to remove the symlink.  We must however deal with the possibility
 	 * that it's a directory instead of a symlink --- this could happen during
-	 * WAL replay (see TablespaceCreateDbspace), and it is also the case on
-	 * Windows where junction points lstat() as directories.
+	 * WAL replay (see TablespaceCreateDbspace).
 	 *
 	 * Note: in the redo case, we'll return true if this final step fails;
 	 * there's no point in retrying it.  Also, ENOENT should provoke no more
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 637c0ce459..638de07035 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1320,13 +1320,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
-		if (strcmp(path, "./pg_tblspc") == 0 &&
-#ifndef WIN32
-			S_ISLNK(statbuf.st_mode)
-#else
-			pgwin32_is_junction(pathbuf)
-#endif
-			)
+		if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		linkpath[MAXPGPATH];
@@ -1809,11 +1803,7 @@ static void
 convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
 {
 	/* If symlink, write it as a directory anyway */
-#ifndef WIN32
 	if (S_ISLNK(statbuf->st_mode))
-#else
-	if (pgwin32_is_junction(pathbuf))
-#endif
 		statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
 }
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index f904f60c08..566ebe26a0 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -3377,7 +3377,6 @@ SyncDataDirectory(void)
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -3389,10 +3388,6 @@ SyncDataDirectory(void)
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction("pg_wal"))
-		xlog_is_symlink = true;
-#endif
 
 #ifdef HAVE_SYNCFS
 	if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_SYNCFS)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 89690be2ed..412039ea6b 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -283,9 +283,7 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	char		sourcepath[MAXPGPATH];
 	char		targetpath[MAXPGPATH];
 	int			rllen;
-#ifndef WIN32
 	struct stat st;
-#endif
 
 	/*
 	 * It's useful to apply this function to pg_class.reltablespace, wherein
@@ -316,10 +314,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	 * created with allow_in_place_tablespaces enabled.  If a directory is
 	 * found, a relative path to the data directory is returned.
 	 */
-#ifdef WIN32
-	if (!pgwin32_is_junction(sourcepath))
-		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#else
 	if (lstat(sourcepath, &st) < 0)
 	{
 		ereport(ERROR,
@@ -330,7 +324,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 
 	if (!S_ISLNK(st.st_mode))
 		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#endif
 
 	/*
 	 * In presence of a link or a junction point, return the path pointing to.
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
index dc20122c89..324ccf7783 100644
--- a/src/bin/pg_checksums/pg_checksums.c
+++ b/src/bin/pg_checksums/pg_checksums.c
@@ -384,11 +384,7 @@ scan_directory(const char *basedir, const char *subdir, bool sizeonly)
 			if (!sizeonly)
 				scan_file(fn, segmentno);
 		}
-#ifndef WIN32
 		else if (S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode))
-#else
-		else if (S_ISDIR(st.st_mode) || pgwin32_is_junction(fn))
-#endif
 		{
 			/*
 			 * If going through the entries of pg_tblspc, we assume to operate
diff --git a/src/bin/pg_rewind/file_ops.c b/src/bin/pg_rewind/file_ops.c
index 6cb288f099..7d98283c79 100644
--- a/src/bin/pg_rewind/file_ops.c
+++ b/src/bin/pg_rewind/file_ops.c
@@ -431,11 +431,7 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/* recurse to handle subdirectories */
 			recurse_dir(datadir, path, callback);
 		}
-#ifndef WIN32
 		else if (S_ISLNK(fst.st_mode))
-#else
-		else if (pgwin32_is_junction(fullpath))
-#endif
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		link_target[MAXPGPATH];
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 966b987d64..71c232d983 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
@@ -465,21 +460,5 @@ get_dirent_type(const char *path,
 #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;
 }
diff --git a/src/include/port.h b/src/include/port.h
index d39b04141f..4b978f61bd 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -284,7 +284,6 @@ extern int	pgunlink(const char *path);
 #if defined(WIN32) && !defined(__CYGWIN__)
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b8cf2e1480..72a0dd572e 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -238,7 +238,6 @@ int			setitimer(int which, const struct itimerval *value, struct itimerval *oval
  */
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 7ce042e75d..01f9d1362b 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -111,6 +111,19 @@ pgunlink(const char *path)
 	{
 		if (errno != EACCES)
 			return -1;
+
+		/*
+		 * Also try with rmdir(), because that's how you remove junction
+		 * points.  Since we pretend junction points are symlinks, various code
+		 * might try to call unlink().  We'll preserve unlink()'s errno though;
+		 * if we got ENOENT then unlink() will presumably return the same next
+		 * time around, ENOTEMPTY shouldn't be possible for a junction point,
+		 * and EACCES is what unlink() returned.
+		 */
+		if (rmdir(path) == 0)
+				break;
+		errno = EACCES;
+
 		if (++loops > 100)		/* time out after 10 sec */
 			return -1;
 		pg_usleep(100000);		/* us */
@@ -336,20 +349,4 @@ pgreadlink(const char *path, char *buf, size_t size)
 	return r;
 }
 
-/*
- * Assumes the file exists, so will return false if it doesn't
- * (since a nonexistent file is not a junction)
- */
-bool
-pgwin32_is_junction(const char *path)
-{
-	DWORD		attr = GetFileAttributes(path);
-
-	if (attr == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return false;
-	}
-	return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
-}
 #endif							/* defined(WIN32) && !defined(__CYGWIN__) */
-- 
2.36.1

From c89ee0d78944e05fa28c1d6c2939d94b6e39987a Mon Sep 17 00:00:00 2001
From: Melih Mutlu <memutlu@microsoft.com>
Date: Mon, 21 Feb 2022 14:46:05 +0300
Subject: [PATCH v3 1/4] Added Windows with MinGW environment in Cirrus CI

---
 .cirrus.yml | 79 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 65 insertions(+), 14 deletions(-)

diff --git a/.cirrus.yml b/.cirrus.yml
index 72735d225a..8decef68e8 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -23,7 +23,6 @@ env:
   CHECKFLAGS: -Otarget
   PROVE_FLAGS: --timer
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
-  TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
   PG_TEST_EXTRA: kerberos ldap ssl
 
 
@@ -338,13 +337,30 @@ task:
     cores_script: src/tools/ci/cores_backtrace.sh macos "${HOME}/cores"
 
 
+WINDOWS_ENVIRONMENT_BASE: &WINDOWS_ENVIRONMENT_BASE
+    env:
+      # Half the allowed per-user CPU cores
+      CPUS: 4
+      # The default working dir is in a directory msbuild complains about
+      CIRRUS_WORKING_DIR: "c:/cirrus"
+      TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
+
+      # Avoids port conflicts between concurrent tap test runs
+      PG_TEST_USE_UNIX_SOCKETS: 1
+
+    only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*windows.*'
+
+    sysinfo_script: |
+      chcp
+      systeminfo
+      powershell -Command get-psdrive -psprovider filesystem
+      set
+
 task:
+  << : *WINDOWS_ENVIRONMENT_BASE
   name: Windows - Server 2019, VS 2019
 
   env:
-    # Half the allowed per-user CPU cores
-    CPUS: 4
-
     # Our windows infrastructure doesn't have test concurrency above the level
     # of a single vcregress test target. Due to that, it's useful to run prove
     # with multiple jobs. For the other tasks it isn't, because two sources
@@ -354,15 +370,11 @@ task:
     # likely can be improved upon further.
     PROVE_FLAGS: -j10 --timer
 
-    # The default cirrus working dir is in a directory msbuild complains about
-    CIRRUS_WORKING_DIR: "c:/cirrus"
     # Avoid re-installing over and over
     NO_TEMP_INSTALL: 1
     # git's tar doesn't deal with drive letters, see
     # https://postgr.es/m/b6782dc3-a7b0-ed56-175f-f8f54cb08d67%40dunslane.net
     TAR: "c:/windows/system32/tar.exe"
-    # Avoids port conflicts between concurrent tap test runs
-    PG_TEST_USE_UNIX_SOCKETS: 1
     PG_REGRESS_SOCK_DIR: "c:/cirrus/"
     # -m enables parallelism
     # verbosity:minimal + Summary reduce verbosity, while keeping a summary of
@@ -393,12 +405,6 @@ task:
     cpu: $CPUS
     memory: 4G
 
-  sysinfo_script: |
-    chcp
-    systeminfo
-    powershell -Command get-psdrive -psprovider filesystem
-    set
-
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
@@ -456,6 +462,51 @@ task:
       path: "crashlog-*.txt"
       type: text/plain
 
+task:
+  << : *WINDOWS_ENVIRONMENT_BASE
+  name: Windows - Server 2019, MinGW64
+  windows_container:
+    image: $CONTAINER_REPO/windows_ci_mingw64:latest
+    cpu: $CPUS
+    memory: 4G
+  env:
+    CCACHE_DIR: C:/msys64/ccache
+    BUILD_DIR: "%CIRRUS_WORKING_DIR%/build"
+
+  ccache_cache:
+    folder: ${CCACHE_DIR}
+
+  mingw_info_script:
+    - C:\msys64\usr\bin\bash.exe -lc "where gcc"
+    - C:\msys64\usr\bin\bash.exe -lc "gcc --version"
+    - C:\msys64\usr\bin\bash.exe -lc "where perl"
+    - C:\msys64\usr\bin\bash.exe -lc "perl --version"
+
+  configure_script:
+    - C:\msys64\usr\bin\bash.exe -lc "mkdir %BUILD_DIR% &&
+      cd %BUILD_DIR% &&
+      %CIRRUS_WORKING_DIR%/configure
+        --host=x86_64-w64-mingw32
+        --enable-cassert
+        --enable-tap-tests
+        --with-icu
+        --with-libxml
+        --with-libxslt
+        --with-lz4
+        --enable-debug
+        CC='ccache gcc'
+        CXX='ccache g++'"
+
+  build_script:
+    C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s world-bin -j${CPUS}"
+
+  upload_caches: ccache
+
+  tests_script:
+  - set "NoDefaultCurrentDirectoryInExePath=0"
+  - C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s ${CHECK} ${CHECKFLAGS} -j${CPUS} TMPDIR=%BUILD_DIR%/tmp_install"
+
+  on_failure: *on_failure
 
 task:
   name: CompilerWarnings
-- 
2.37.1

From 5e64700facc43fd937349bc8d843b15abb8da5cc Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 28 Jul 2022 15:19:38 +1200
Subject: [PATCH v3 2/4] Provide lstat() for Windows.

Junction points will be reported with S_ISLNK(x.st_mode), like in POSIX.
stat() will follow symlinks, like in POSIX (but only one level before it
gives up, unlike in POSIX).

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/include/port/win32_port.h | 18 +++++++-
 src/port/win32stat.c          | 79 +++++++++++++++++++++++++++++++++--
 2 files changed, 92 insertions(+), 5 deletions(-)

diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index 4de5bf3bf6..b8cf2e1480 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -286,10 +286,11 @@ struct stat						/* This should match struct __stat64 */
 
 extern int	_pgfstat64(int fileno, struct stat *buf);
 extern int	_pgstat64(const char *name, struct stat *buf);
+extern int	_pglstat64(const char *name, struct stat *buf);
 
 #define fstat(fileno, sb)	_pgfstat64(fileno, sb)
 #define stat(path, sb)		_pgstat64(path, sb)
-#define lstat(path, sb)		_pgstat64(path, sb)
+#define lstat(path, sb)		_pglstat64(path, sb)
 
 /* These macros are not provided by older MinGW, nor by MSVC */
 #ifndef S_IRUSR
@@ -335,6 +336,21 @@ extern int	_pgstat64(const char *name, struct stat *buf);
 #define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
 #endif
 
+/*
+ * In order for lstat() to be able to report junction points as symlinks, we
+ * need to hijack a bit in st_mode, since neither MSVC nor MinGW provides
+ * S_ISLNK and there aren't any spare bits.  We'll steal the one for character
+ * devices, because we don't otherwise make use of those.
+ */
+#ifdef S_ISLNK
+#error "S_ISLNK is already defined"
+#endif
+#ifdef S_IFLNK
+#error "S_IFLNK is already defined"
+#endif
+#define S_IFLNK S_IFCHR
+#define S_ISLNK(m) (((m) & S_IFLNK) == S_IFLNK)
+
 /*
  * Supplement to <fcntl.h>.
  * This is the same value as _O_NOINHERIT in the MS header file. This is
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index e03ed5f35c..686c510fed 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -15,7 +15,11 @@
 
 #ifdef WIN32
 
+#define UMDF_USING_NTSTATUS
+
 #include "c.h"
+#include "port/win32ntdll.h"
+
 #include <windows.h>
 
 /*
@@ -107,12 +111,10 @@ fileinfo_to_stat(HANDLE hFile, struct stat *buf)
 }
 
 /*
- * Windows implementation of stat().
- *
- * This currently also implements lstat(), though perhaps that should change.
+ * Windows implementation of lstat().
  */
 int
-_pgstat64(const char *name, struct stat *buf)
+_pglstat64(const char *name, struct stat *buf)
 {
 	/*
 	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
@@ -129,10 +131,79 @@ _pgstat64(const char *name, struct stat *buf)
 
 	ret = fileinfo_to_stat(hFile, buf);
 
+	/*
+	 * Unfortunately it's not possible for fileinfo_to_stat() to see a
+	 * FILE_ATTRIBUTE_REPARSE_POINT flag with just a handle, so at this point
+	 * junction points appear as directories.  Ask for the full attributes
+	 * while we still have the handle open.  Someone else can unlink the file
+	 * while we have it open, but they can't create another file with the same
+	 * name.
+	 */
+	if (ret == 0 && S_ISDIR(buf->st_mode))
+	{
+		DWORD		attr;
+
+		attr = GetFileAttributes(name);
+		if (attr == INVALID_FILE_ATTRIBUTES)
+		{
+			DWORD		err;
+
+			/* If it's been unlinked since we opened it, report as ENOENT. */
+			err = GetLastError();
+			if (err == ERROR_ACCESS_DENIED &&
+				pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
+				errno = ENOENT;
+			else
+				_dosmaperr(err);
+
+			ret = -1;
+		}
+		else if (attr & FILE_ATTRIBUTE_REPARSE_POINT)
+		{
+			buf->st_mode &= ~S_IFDIR;
+			buf->st_mode |= S_IFLNK;
+		}
+	}
+
 	CloseHandle(hFile);
 	return ret;
 }
 
+/*
+ * Windows implementation of stat().
+ */
+int
+_pgstat64(const char *name, struct stat *buf)
+{
+	int			ret;
+
+	ret = _pglstat64(name, buf);
+
+	/* Do we need to follow a symlink (junction point)? */
+	if (ret == 0 && S_ISLNK(buf->st_mode))
+	{
+		char		next[MAXPGPATH];
+
+		if (readlink(name, next, sizeof(next)) < 0)
+			return -1;
+
+		ret = _pglstat64(next, buf);
+		if (ret == 0 && S_ISLNK(buf->st_mode))
+		{
+			/*
+			 * We're only prepared to go one hop, because we only expect to
+			 * deal with the simple cases that we create.  The error for too
+			 * many symlinks is supposed to be ELOOP, but Windows hasn't got
+			 * it.
+			 */
+			errno = EIO;
+			return -1;
+		}
+	}
+
+	return ret;
+}
+
 /*
  * Windows implementation of fstat().
  */
-- 
2.37.1

From 77925ac5fa68b0915bd309d977c85ecf1128f9fc Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Mon, 1 Aug 2022 15:43:13 +1200
Subject: [PATCH v3 3/4] Make unlink() work for junction points on Windows.

To support harmonization of Windows and Unix code, teach our unlink()
wrapper that junction points need to be unlinked with rmdir() on
Windows.

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/port/dirmod.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 7ce042e75d..ea191e99c6 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -99,6 +99,32 @@ int
 pgunlink(const char *path)
 {
 	int			loops = 0;
+	struct stat st;
+
+	/*
+	 * This function might be called for a regular file or for a junction
+	 * point (which we use to emulate symlinks).  The latter must be unlinked
+	 * with rmdir() on Windows.  Before we worry about any of that, let's see
+	 * if we can unlink directly, since that's expected to be the most common
+	 * case.
+	 */
+	if (unlink(path) == 0)
+		return 0;
+	if (errno != EACCES)
+		return -1;
+
+	/*
+	 * EACCES is reported for many reasons including unlink() of a junction
+	 * point.  Check if that's the case so we can redirect to rmdir().
+	 *
+	 * Note that by checking only once, we can't cope with a path that changes
+	 * from regular file to junction point underneath us while we're retrying
+	 * due to sharing violations, but that seems unlikely.  We could perhaps
+	 * prevent that by holding a file handle ourselves across the lstat() and
+	 * the retry loop, but that seems like over-engineering for now.
+	 */
+	if (lstat(path, &st) < 0)
+		return -1;
 
 	/*
 	 * We need to loop because even though PostgreSQL uses flags that allow
@@ -107,7 +133,7 @@ pgunlink(const char *path)
 	 * someone else to close the file, as the caller might be holding locks
 	 * and blocking other backends.
 	 */
-	while (unlink(path))
+	while ((S_ISLNK(st.st_mode) ? rmdir(path) : unlink(path)) < 0)
 	{
 		if (errno != EACCES)
 			return -1;
-- 
2.37.1

From 4391644be135e15ffb052594c4ae54c4d83569df Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 28 Jul 2022 15:25:10 +1200
Subject: [PATCH v3 4/4] Replace pgwin32_is_junction() with lstat().

Now that lstat() reports junction points with S_IFLNK and unlink() can
unlink them, there is no need for separate code paths for Windows in a
few places.

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 tries to deal with that by retrying.

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/backend/commands/tablespace.c    |  3 +--
 src/backend/replication/basebackup.c | 12 +-----------
 src/backend/storage/file/fd.c        |  5 -----
 src/backend/utils/adt/misc.c         |  7 -------
 src/bin/pg_checksums/pg_checksums.c  |  4 ----
 src/bin/pg_rewind/file_ops.c         |  4 ----
 src/common/file_utils.c              | 21 ---------------------
 src/include/port.h                   |  1 -
 src/include/port/win32_port.h        |  1 -
 src/port/dirmod.c                    | 16 ----------------
 10 files changed, 2 insertions(+), 72 deletions(-)

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 570ce3dbd5..dc0d7befd9 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -805,8 +805,7 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
 	/*
 	 * Try to remove the symlink.  We must however deal with the possibility
 	 * that it's a directory instead of a symlink --- this could happen during
-	 * WAL replay (see TablespaceCreateDbspace), and it is also the case on
-	 * Windows where junction points lstat() as directories.
+	 * WAL replay (see TablespaceCreateDbspace).
 	 *
 	 * Note: in the redo case, we'll return true if this final step fails;
 	 * there's no point in retrying it.  Also, ENOENT should provoke no more
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 7f85071229..a048cd5f31 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1322,13 +1322,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
-		if (strcmp(path, "./pg_tblspc") == 0 &&
-#ifndef WIN32
-			S_ISLNK(statbuf.st_mode)
-#else
-			pgwin32_is_junction(pathbuf)
-#endif
-			)
+		if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		linkpath[MAXPGPATH];
@@ -1811,11 +1805,7 @@ static void
 convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
 {
 	/* If symlink, write it as a directory anyway */
-#ifndef WIN32
 	if (S_ISLNK(statbuf->st_mode))
-#else
-	if (pgwin32_is_junction(pathbuf))
-#endif
 		statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
 }
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index f904f60c08..566ebe26a0 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -3377,7 +3377,6 @@ SyncDataDirectory(void)
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -3389,10 +3388,6 @@ SyncDataDirectory(void)
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction("pg_wal"))
-		xlog_is_symlink = true;
-#endif
 
 #ifdef HAVE_SYNCFS
 	if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_SYNCFS)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 89690be2ed..412039ea6b 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -283,9 +283,7 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	char		sourcepath[MAXPGPATH];
 	char		targetpath[MAXPGPATH];
 	int			rllen;
-#ifndef WIN32
 	struct stat st;
-#endif
 
 	/*
 	 * It's useful to apply this function to pg_class.reltablespace, wherein
@@ -316,10 +314,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	 * created with allow_in_place_tablespaces enabled.  If a directory is
 	 * found, a relative path to the data directory is returned.
 	 */
-#ifdef WIN32
-	if (!pgwin32_is_junction(sourcepath))
-		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#else
 	if (lstat(sourcepath, &st) < 0)
 	{
 		ereport(ERROR,
@@ -330,7 +324,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 
 	if (!S_ISLNK(st.st_mode))
 		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#endif
 
 	/*
 	 * In presence of a link or a junction point, return the path pointing to.
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
index dc20122c89..324ccf7783 100644
--- a/src/bin/pg_checksums/pg_checksums.c
+++ b/src/bin/pg_checksums/pg_checksums.c
@@ -384,11 +384,7 @@ scan_directory(const char *basedir, const char *subdir, bool sizeonly)
 			if (!sizeonly)
 				scan_file(fn, segmentno);
 		}
-#ifndef WIN32
 		else if (S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode))
-#else
-		else if (S_ISDIR(st.st_mode) || pgwin32_is_junction(fn))
-#endif
 		{
 			/*
 			 * If going through the entries of pg_tblspc, we assume to operate
diff --git a/src/bin/pg_rewind/file_ops.c b/src/bin/pg_rewind/file_ops.c
index 6cb288f099..7d98283c79 100644
--- a/src/bin/pg_rewind/file_ops.c
+++ b/src/bin/pg_rewind/file_ops.c
@@ -431,11 +431,7 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/* recurse to handle subdirectories */
 			recurse_dir(datadir, path, callback);
 		}
-#ifndef WIN32
 		else if (S_ISLNK(fst.st_mode))
-#else
-		else if (pgwin32_is_junction(fullpath))
-#endif
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		link_target[MAXPGPATH];
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 966b987d64..71c232d983 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
@@ -465,21 +460,5 @@ get_dirent_type(const char *path,
 #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;
 }
diff --git a/src/include/port.h b/src/include/port.h
index d39b04141f..4b978f61bd 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -284,7 +284,6 @@ extern int	pgunlink(const char *path);
 #if defined(WIN32) && !defined(__CYGWIN__)
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b8cf2e1480..72a0dd572e 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -238,7 +238,6 @@ int			setitimer(int which, const struct itimerval *value, struct itimerval *oval
  */
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index ea191e99c6..2818bfd2e9 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -362,20 +362,4 @@ pgreadlink(const char *path, char *buf, size_t size)
 	return r;
 }
 
-/*
- * Assumes the file exists, so will return false if it doesn't
- * (since a nonexistent file is not a junction)
- */
-bool
-pgwin32_is_junction(const char *path)
-{
-	DWORD		attr = GetFileAttributes(path);
-
-	if (attr == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return false;
-	}
-	return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
-}
 #endif							/* defined(WIN32) && !defined(__CYGWIN__) */
-- 
2.37.1

From 6e57c91b7b780ea51fa45e63cb201ff4240a416b Mon Sep 17 00:00:00 2001
From: Melih Mutlu <memutlu@microsoft.com>
Date: Mon, 21 Feb 2022 14:46:05 +0300
Subject: [PATCH v4 1/4] Added Windows with MinGW environment in Cirrus CI

---
 .cirrus.yml | 79 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 65 insertions(+), 14 deletions(-)

diff --git a/.cirrus.yml b/.cirrus.yml
index 81eb8a9996..9820915f35 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -23,7 +23,6 @@ env:
   CHECKFLAGS: -Otarget
   PROVE_FLAGS: --timer
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
-  TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
   PG_TEST_EXTRA: kerberos ldap ssl
 
 
@@ -338,13 +337,30 @@ task:
     cores_script: src/tools/ci/cores_backtrace.sh macos "${HOME}/cores"
 
 
+WINDOWS_ENVIRONMENT_BASE: &WINDOWS_ENVIRONMENT_BASE
+    env:
+      # Half the allowed per-user CPU cores
+      CPUS: 4
+      # The default working dir is in a directory msbuild complains about
+      CIRRUS_WORKING_DIR: "c:/cirrus"
+      TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
+
+      # Avoids port conflicts between concurrent tap test runs
+      PG_TEST_USE_UNIX_SOCKETS: 1
+
+    only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*windows.*'
+
+    sysinfo_script: |
+      chcp
+      systeminfo
+      powershell -Command get-psdrive -psprovider filesystem
+      set
+
 task:
+  << : *WINDOWS_ENVIRONMENT_BASE
   name: Windows - Server 2019, VS 2019
 
   env:
-    # Half the allowed per-user CPU cores
-    CPUS: 4
-
     # Our windows infrastructure doesn't have test concurrency above the level
     # of a single vcregress test target. Due to that, it's useful to run prove
     # with multiple jobs. For the other tasks it isn't, because two sources
@@ -354,15 +370,11 @@ task:
     # likely can be improved upon further.
     PROVE_FLAGS: -j10 --timer
 
-    # The default cirrus working dir is in a directory msbuild complains about
-    CIRRUS_WORKING_DIR: "c:/cirrus"
     # Avoid re-installing over and over
     NO_TEMP_INSTALL: 1
     # git's tar doesn't deal with drive letters, see
     # https://postgr.es/m/b6782dc3-a7b0-ed56-175f-f8f54cb08d67%40dunslane.net
     TAR: "c:/windows/system32/tar.exe"
-    # Avoids port conflicts between concurrent tap test runs
-    PG_TEST_USE_UNIX_SOCKETS: 1
     PG_REGRESS_SOCK_DIR: "c:/cirrus/"
     # -m enables parallelism
     # verbosity:minimal + Summary reduce verbosity, while keeping a summary of
@@ -393,12 +405,6 @@ task:
     cpu: $CPUS
     memory: 4G
 
-  sysinfo_script: |
-    chcp
-    systeminfo
-    powershell -Command get-psdrive -psprovider filesystem
-    set
-
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
@@ -456,6 +462,51 @@ task:
       path: "crashlog-*.txt"
       type: text/plain
 
+task:
+  << : *WINDOWS_ENVIRONMENT_BASE
+  name: Windows - Server 2019, MinGW64
+  windows_container:
+    image: $CONTAINER_REPO/windows_ci_mingw64:latest
+    cpu: $CPUS
+    memory: 4G
+  env:
+    CCACHE_DIR: C:/msys64/ccache
+    BUILD_DIR: "%CIRRUS_WORKING_DIR%/build"
+
+  ccache_cache:
+    folder: ${CCACHE_DIR}
+
+  mingw_info_script:
+    - C:\msys64\usr\bin\bash.exe -lc "where gcc"
+    - C:\msys64\usr\bin\bash.exe -lc "gcc --version"
+    - C:\msys64\usr\bin\bash.exe -lc "where perl"
+    - C:\msys64\usr\bin\bash.exe -lc "perl --version"
+
+  configure_script:
+    - C:\msys64\usr\bin\bash.exe -lc "mkdir %BUILD_DIR% &&
+      cd %BUILD_DIR% &&
+      %CIRRUS_WORKING_DIR%/configure
+        --host=x86_64-w64-mingw32
+        --enable-cassert
+        --enable-tap-tests
+        --with-icu
+        --with-libxml
+        --with-libxslt
+        --with-lz4
+        --enable-debug
+        CC='ccache gcc'
+        CXX='ccache g++'"
+
+  build_script:
+    C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s world-bin -j${CPUS}"
+
+  upload_caches: ccache
+
+  tests_script:
+  - set "NoDefaultCurrentDirectoryInExePath=0"
+  - C:\msys64\usr\bin\bash.exe -lc "cd %BUILD_DIR% && make -s ${CHECK} ${CHECKFLAGS} -j${CPUS} TMPDIR=%BUILD_DIR%/tmp_install"
+
+  on_failure: *on_failure
 
 task:
   name: CompilerWarnings
-- 
2.37.1

From f8be96a1c712b7ffe42445108022b9978825ce97 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Fri, 5 Aug 2022 16:41:34 +1200
Subject: [PATCH v4 2/4] Provide lstat() for Windows.

Junction points will be reported with S_ISLNK(x.st_mode), simulating
POSIX lstat().  stat() will follow pseudo-symlinks, like in POSIX (but
only one level before giving up, unlike in POSIX).

Tested-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/include/port/win32_port.h |  18 +++++-
 src/port/win32stat.c          | 104 ++++++++++++++++++++++++++++++++--
 2 files changed, 117 insertions(+), 5 deletions(-)

diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index 0eaa97561a..c27b34de5b 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -278,10 +278,11 @@ struct stat						/* This should match struct __stat64 */
 
 extern int	_pgfstat64(int fileno, struct stat *buf);
 extern int	_pgstat64(const char *name, struct stat *buf);
+extern int	_pglstat64(const char *name, struct stat *buf);
 
 #define fstat(fileno, sb)	_pgfstat64(fileno, sb)
 #define stat(path, sb)		_pgstat64(path, sb)
-#define lstat(path, sb)		_pgstat64(path, sb)
+#define lstat(path, sb)		_pglstat64(path, sb)
 
 /* These macros are not provided by older MinGW, nor by MSVC */
 #ifndef S_IRUSR
@@ -327,6 +328,21 @@ extern int	_pgstat64(const char *name, struct stat *buf);
 #define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
 #endif
 
+/*
+ * In order for lstat() to be able to report junction points as symlinks, we
+ * need to hijack a bit in st_mode, since neither MSVC nor MinGW provides
+ * S_ISLNK and there aren't any spare bits.  We'll steal the one for character
+ * devices, because we don't otherwise make use of those.
+ */
+#ifdef S_ISLNK
+#error "S_ISLNK is already defined"
+#endif
+#ifdef S_IFLNK
+#error "S_IFLNK is already defined"
+#endif
+#define S_IFLNK S_IFCHR
+#define S_ISLNK(m) (((m) & S_IFLNK) == S_IFLNK)
+
 /*
  * Supplement to <fcntl.h>.
  * This is the same value as _O_NOINHERIT in the MS header file. This is
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index e03ed5f35c..b10e35886e 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -15,7 +15,11 @@
 
 #ifdef WIN32
 
+#define UMDF_USING_NTSTATUS
+
 #include "c.h"
+#include "port/win32ntdll.h"
+
 #include <windows.h>
 
 /*
@@ -107,12 +111,10 @@ fileinfo_to_stat(HANDLE hFile, struct stat *buf)
 }
 
 /*
- * Windows implementation of stat().
- *
- * This currently also implements lstat(), though perhaps that should change.
+ * Windows implementation of lstat().
  */
 int
-_pgstat64(const char *name, struct stat *buf)
+_pglstat64(const char *name, struct stat *buf)
 {
 	/*
 	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
@@ -129,10 +131,104 @@ _pgstat64(const char *name, struct stat *buf)
 
 	ret = fileinfo_to_stat(hFile, buf);
 
+	/*
+	 * Junction points appear as directories to fileinfo_to_stat(), so we'll
+	 * need to do a bit more work to distinguish them.
+	 */
+	if (ret == 0 && S_ISDIR(buf->st_mode))
+	{
+		char		next[MAXPGPATH];
+		ssize_t		size;
+
+		/*
+		 * POSIX says we need to put the length of the target path into
+		 * st_size.  Use readlink() to get it, or learn that this is not a
+		 * junction point.
+		 */
+		size = readlink(name, next, sizeof(next));
+		if (size < 0)
+		{
+			if (errno == EACCES &&
+				pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
+			{
+				/* Unlinked underneath us. */
+				errno = ENOENT;
+				ret = -1;
+			}
+			else if (errno == EINVAL)
+			{
+				/* It's not a junction point, nothing to do. */
+			}
+			else
+			{
+				/* Some other failure. */
+				ret = -1;
+			}
+		}
+		else
+		{
+			/* It's a junction point, so report it as a symlink. */
+			buf->st_mode &= ~S_IFDIR;
+			buf->st_mode |= S_IFLNK;
+			buf->st_size = size;
+		}
+	}
+
 	CloseHandle(hFile);
 	return ret;
 }
 
+/*
+ * Windows implementation of stat().
+ */
+int
+_pgstat64(const char *name, struct stat *buf)
+{
+	int			ret;
+
+	ret = _pglstat64(name, buf);
+
+	/* Do we need to follow a symlink (junction point)? */
+	if (ret == 0 && S_ISLNK(buf->st_mode))
+	{
+		char		next[MAXPGPATH];
+		ssize_t		size;
+
+		size = readlink(name, next, sizeof(next));
+		if (size < 0)
+		{
+			if (errno == EACCES &&
+				pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
+			{
+				/* Unlinked underneath us. */
+				errno = ENOENT;
+			}
+			return -1;
+		}
+		if (size >= sizeof(next))
+		{
+			errno = ENAMETOOLONG;
+			return -1;
+		}
+		next[size] = 0;
+
+		ret = _pglstat64(next, buf);
+		if (ret == 0 && S_ISLNK(buf->st_mode))
+		{
+			/*
+			 * We're only prepared to go one hop, because we only expect to
+			 * deal with the simple cases that we create.  The error for too
+			 * many symlinks is supposed to be ELOOP, but Windows hasn't got
+			 * it.
+			 */
+			errno = EIO;
+			return -1;
+		}
+	}
+
+	return ret;
+}
+
 /*
  * Windows implementation of fstat().
  */
-- 
2.37.1

From 9fa720ed83ea394a5c701a9ec4aee3336d23b6b0 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Fri, 5 Aug 2022 09:52:26 +1200
Subject: [PATCH v4 4/4] Replace pgwin32_is_junction() with lstat().

Now that lstat() reports junction points with S_IFLNK and unlink() can
unlink them, there is no need for conditional code for Windows in a few
places.  Sometimes that was expressed by testing for WIN32, other times
by testing for S_ISLNK.

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 only because
lstat() didn't previously work for symlinks (junction points), but isn't
needed anymore.

Tested-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/backend/commands/tablespace.c    |  7 +------
 src/backend/replication/basebackup.c | 12 +-----------
 src/backend/storage/file/fd.c        |  5 -----
 src/backend/utils/adt/misc.c         |  7 -------
 src/bin/pg_checksums/pg_checksums.c  |  4 ----
 src/bin/pg_rewind/file_ops.c         |  4 ----
 src/common/file_utils.c              | 23 -----------------------
 src/include/port.h                   |  1 -
 src/include/port/win32_port.h        |  1 -
 src/port/dirmod.c                    | 16 ----------------
 10 files changed, 2 insertions(+), 78 deletions(-)

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 526e82e388..f260b484fc 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -792,8 +792,7 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
 	/*
 	 * Try to remove the symlink.  We must however deal with the possibility
 	 * that it's a directory instead of a symlink --- this could happen during
-	 * WAL replay (see TablespaceCreateDbspace), and it is also the case on
-	 * Windows where junction points lstat() as directories.
+	 * WAL replay (see TablespaceCreateDbspace).
 	 *
 	 * Note: in the redo case, we'll return true if this final step fails;
 	 * there's no point in retrying it.  Also, ENOENT should provoke no more
@@ -823,7 +822,6 @@ remove_symlink:
 							linkloc)));
 		}
 	}
-#ifdef S_ISLNK
 	else if (S_ISLNK(st.st_mode))
 	{
 		if (unlink(linkloc) < 0)
@@ -836,7 +834,6 @@ remove_symlink:
 							linkloc)));
 		}
 	}
-#endif
 	else
 	{
 		/* Refuse to remove anything that's not a directory or symlink */
@@ -914,7 +911,6 @@ remove_tablespace_symlink(const char *linkloc)
 					 errmsg("could not remove directory \"%s\": %m",
 							linkloc)));
 	}
-#ifdef S_ISLNK
 	else if (S_ISLNK(st.st_mode))
 	{
 		if (unlink(linkloc) < 0 && errno != ENOENT)
@@ -923,7 +919,6 @@ remove_tablespace_symlink(const char *linkloc)
 					 errmsg("could not remove symbolic link \"%s\": %m",
 							linkloc)));
 	}
-#endif
 	else
 	{
 		/* Refuse to remove anything that's not a directory or symlink */
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 5e457f9be9..deeddd09a9 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1322,13 +1322,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
-		if (strcmp(path, "./pg_tblspc") == 0 &&
-#ifndef WIN32
-			S_ISLNK(statbuf.st_mode)
-#else
-			pgwin32_is_junction(pathbuf)
-#endif
-			)
+		if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
 		{
 			char		linkpath[MAXPGPATH];
 			int			rllen;
@@ -1798,11 +1792,7 @@ static void
 convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
 {
 	/* If symlink, write it as a directory anyway */
-#ifndef WIN32
 	if (S_ISLNK(statbuf->st_mode))
-#else
-	if (pgwin32_is_junction(pathbuf))
-#endif
 		statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
 }
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index ccb540d617..efb34d4dcb 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -3365,7 +3365,6 @@ SyncDataDirectory(void)
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -3377,10 +3376,6 @@ SyncDataDirectory(void)
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction("pg_wal"))
-		xlog_is_symlink = true;
-#endif
 
 #ifdef HAVE_SYNCFS
 	if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_SYNCFS)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index af0d924459..d35b5d1f4f 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -283,9 +283,7 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	char		sourcepath[MAXPGPATH];
 	char		targetpath[MAXPGPATH];
 	int			rllen;
-#ifndef WIN32
 	struct stat st;
-#endif
 
 	/*
 	 * It's useful to apply this function to pg_class.reltablespace, wherein
@@ -314,10 +312,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	 * created with allow_in_place_tablespaces enabled.  If a directory is
 	 * found, a relative path to the data directory is returned.
 	 */
-#ifdef WIN32
-	if (!pgwin32_is_junction(sourcepath))
-		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#else
 	if (lstat(sourcepath, &st) < 0)
 	{
 		ereport(ERROR,
@@ -328,7 +322,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 
 	if (!S_ISLNK(st.st_mode))
 		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#endif
 
 	/*
 	 * In presence of a link or a junction point, return the path pointing to.
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
index dc20122c89..324ccf7783 100644
--- a/src/bin/pg_checksums/pg_checksums.c
+++ b/src/bin/pg_checksums/pg_checksums.c
@@ -384,11 +384,7 @@ scan_directory(const char *basedir, const char *subdir, bool sizeonly)
 			if (!sizeonly)
 				scan_file(fn, segmentno);
 		}
-#ifndef WIN32
 		else if (S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode))
-#else
-		else if (S_ISDIR(st.st_mode) || pgwin32_is_junction(fn))
-#endif
 		{
 			/*
 			 * If going through the entries of pg_tblspc, we assume to operate
diff --git a/src/bin/pg_rewind/file_ops.c b/src/bin/pg_rewind/file_ops.c
index 5e6d8b89c4..db190bcba7 100644
--- a/src/bin/pg_rewind/file_ops.c
+++ b/src/bin/pg_rewind/file_ops.c
@@ -431,11 +431,7 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/* recurse to handle subdirectories */
 			recurse_dir(datadir, path, callback);
 		}
-#ifndef WIN32
 		else if (S_ISLNK(fst.st_mode))
-#else
-		else if (pgwin32_is_junction(fullpath))
-#endif
 		{
 			char		link_target[MAXPGPATH];
 			int			len;
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 966b987d64..df4d6d240c 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;
 }
diff --git a/src/include/port.h b/src/include/port.h
index 14b640fe33..feb2ae840d 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -284,7 +284,6 @@ extern int	pgunlink(const char *path);
 #if defined(WIN32) && !defined(__CYGWIN__)
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index c27b34de5b..a65996cce5 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -230,7 +230,6 @@ int			setitimer(int which, const struct itimerval *value, struct itimerval *oval
  */
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index ea191e99c6..2818bfd2e9 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -362,20 +362,4 @@ pgreadlink(const char *path, char *buf, size_t size)
 	return r;
 }
 
-/*
- * Assumes the file exists, so will return false if it doesn't
- * (since a nonexistent file is not a junction)
- */
-bool
-pgwin32_is_junction(const char *path)
-{
-	DWORD		attr = GetFileAttributes(path);
-
-	if (attr == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return false;
-	}
-	return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
-}
 #endif							/* defined(WIN32) && !defined(__CYGWIN__) */
-- 
2.37.1

From af3e1f2e5fd505299d9062a8aedc6765983aebc2 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Fri, 5 Aug 2022 16:41:50 +1200
Subject: [PATCH v4 3/4] Make unlink() work for junction points on Windows.

To support harmonization of Windows and Unix code, teach our unlink()
wrapper that junction points need to be unlinked with rmdir() on
Windows.

Tested-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/port/dirmod.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 7ce042e75d..ea191e99c6 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -99,6 +99,32 @@ int
 pgunlink(const char *path)
 {
 	int			loops = 0;
+	struct stat st;
+
+	/*
+	 * This function might be called for a regular file or for a junction
+	 * point (which we use to emulate symlinks).  The latter must be unlinked
+	 * with rmdir() on Windows.  Before we worry about any of that, let's see
+	 * if we can unlink directly, since that's expected to be the most common
+	 * case.
+	 */
+	if (unlink(path) == 0)
+		return 0;
+	if (errno != EACCES)
+		return -1;
+
+	/*
+	 * EACCES is reported for many reasons including unlink() of a junction
+	 * point.  Check if that's the case so we can redirect to rmdir().
+	 *
+	 * Note that by checking only once, we can't cope with a path that changes
+	 * from regular file to junction point underneath us while we're retrying
+	 * due to sharing violations, but that seems unlikely.  We could perhaps
+	 * prevent that by holding a file handle ourselves across the lstat() and
+	 * the retry loop, but that seems like over-engineering for now.
+	 */
+	if (lstat(path, &st) < 0)
+		return -1;
 
 	/*
 	 * We need to loop because even though PostgreSQL uses flags that allow
@@ -107,7 +133,7 @@ pgunlink(const char *path)
 	 * someone else to close the file, as the caller might be holding locks
 	 * and blocking other backends.
 	 */
-	while (unlink(path))
+	while ((S_ISLNK(st.st_mode) ? rmdir(path) : unlink(path)) < 0)
 	{
 		if (errno != EACCES)
 			return -1;
-- 
2.37.1

diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 2818bfd2e95..9d73620a6ba 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -354,7 +354,8 @@ pgreadlink(const char *path, char *buf, size_t size)
 	 * If the path starts with "\??\", which it will do in most (all?) cases,
 	 * strip those out.
 	 */
-	if (r > 4 && strncmp(buf, "\\??\\", 4) == 0)
+	if (r > 4 && strncmp(buf, "\\??\\", 4) == 0 &&
+		strncmp(buf, "\\??\\Volume", 10) != 0)
 	{
 		memmove(buf, buf + 4, strlen(buf + 4) + 1);
 		r -= 4;

From 9772b2bf5a1b11605ea16cfd17b3b50e0274aadf Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Tue, 9 Aug 2022 10:29:08 +1200
Subject: [PATCH] Fix readlink() for more complex Windows paths.

Our symlink() and readlink() replacements perform a very naive
transformation from "DOS" paths to "NT" paths and back, as required by
the junction point APIs.  This was enough for the simple paths we expect
users to provide for tablespaces, for example 'd:\my\fast\storage'.

Since commit c5cb8f3b taught stat() to follow symlinks, and since initdb
uses pg_mkdir_p(), and that examines parent directories, our humble
readlink() implementation can now be exposed to junction points not of
PostgreSQL origin.  Those might be corrupted by our naive path mangling,
which doesn't really understand NT paths in general.

It's possible that we should investigate using Rtl*() library routines
to do path transformation, but for now, simply decline to transform
paths that don't fit the simple drive-qualified pattern.  That means
that readlink() returns an NT path, which works just as well as a DOS
path when following the link.

Reported-by: Roman Zharkov <r.zharkov@postgrespro.ru>
Discussion: https://postgr.es/m/4590c37927d7b8ee84f9855d83229018%40postgrespro.ru
---
 src/port/dirmod.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 2818bfd2e9..821563c290 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -352,9 +352,11 @@ pgreadlink(const char *path, char *buf, size_t size)
 
 	/*
 	 * If the path starts with "\??\", which it will do in most (all?) cases,
-	 * strip those out.
+	 * strip those out, but only if it's of the simple drive-letter-qualified
+	 * type that we know how to transform from NT to DOS format.
 	 */
-	if (r > 4 && strncmp(buf, "\\??\\", 4) == 0)
+	if (r >= 6 && strncmp(buf, "\\??\\", 4) == 0 && isalpha(buf[4]) &&
+		buf[5] == ':')
 	{
 		memmove(buf, buf + 4, strlen(buf + 4) + 1);
 		r -= 4;
-- 
2.35.1

From 6ed3edc77275aa51d1d0b1012c0a36db65735d39 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Thu, 11 Aug 2022 10:42:13 +1200
Subject: [PATCH v2 1/2] Fix readlink() for general Windows junction points.

Our symlink() and readlink() replacements perform a naive transformation
from DOS paths to NT paths and back, as required by the junction point
APIs.  This was enough for the "drive absolute" paths we expect users to
provide for tablespaces, for example "d:\my\fast\storage".

Since commit c5cb8f3b taught stat() to follow symlinks, and since initdb
uses pg_mkdir_p(), and that examines parent directories, our humble
readlink() implementation can now be exposed to junction points not of
PostgreSQL origin.  Those might be corrupted by our naive path mangling,
which doesn't really understand NT paths in general.

Simply decline to transform paths that don't look like a drive absolute
path.  That means that readlink() returns the NT path directly when
checking a parent directory of PGDATA that happen to point to a drive
using "rooted" format.  That  works for the purposes of our stat()
emulation.

Reported-by: Roman Zharkov <r.zharkov@postgrespro.ru>
Discussion: https://postgr.es/m/4590c37927d7b8ee84f9855d83229018%40postgrespro.ru
---
 src/port/dirmod.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index 2818bfd2e9..53310baafb 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -199,7 +199,11 @@ pgsymlink(const char *oldpath, const char *newpath)
 	if (dirhandle == INVALID_HANDLE_VALUE)
 		return -1;
 
-	/* make sure we have an unparsed native win32 path */
+	/*
+	 * We expect either an NT path or a "drive absolute" path like "C:\..."
+	 * that we convert to an NT path by bolting on a prefix and converting any
+	 * Unix-style path delimiters to NT-style.
+	 */
 	if (memcmp("\\??\\", oldpath, 4) != 0)
 		snprintf(nativeTarget, sizeof(nativeTarget), "\\??\\%s", oldpath);
 	else
@@ -351,10 +355,21 @@ pgreadlink(const char *path, char *buf, size_t size)
 	}
 
 	/*
-	 * If the path starts with "\??\", which it will do in most (all?) cases,
-	 * strip those out.
+	 * If the path starts with "\??\" followed by a "drive absolute" path
+	 * (known to Windows APIs as RtlPathTypeDriveAbsolute), then strip that
+	 * prefix.  This undoes some of the transformation performed by
+	 * pqsymlink(), to get back to a format that users are used to seeing.  We
+	 * don't know how to transform other path types that might be encountered
+	 * outside PGDATA, so we just return them directly.
 	 */
-	if (r > 4 && strncmp(buf, "\\??\\", 4) == 0)
+	if (r >= 7 &&
+		buf[0] == '\\' &&
+		buf[1] == '?' &&
+		buf[2] == '?' &&
+		buf[3] == '\\' &&
+		isalpha(buf[4]) &&
+		buf[5] == ':' &&
+		buf[6] == '\\')
 	{
 		memmove(buf, buf + 4, strlen(buf + 4) + 1);
 		r -= 4;
-- 
2.35.1

From 81f203af67bb0dfed1a55656496fd55211d98972 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 11 Aug 2022 12:30:48 +1200
Subject: [PATCH v2 2/2] Follow junction point chains in our stat() emulation.

Commit c5cb8f3b supposed that we'd only ever have to follow junction
points for one hop, because we don't construct longer chains of them
ourselves.  But when stat()ing a parent directory supplied by the user,
we should really be able to cope with longer chains.  Choose an
arbitrary cap of 8, to match the minimum acceptable value of SYMLOOP_MAX
from POSIX.
---
 src/port/win32stat.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 26443293d7..2ff42b9a90 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -184,16 +184,27 @@ _pglstat64(const char *name, struct stat *buf)
 int
 _pgstat64(const char *name, struct stat *buf)
 {
+	int			loops = 0;
 	int			ret;
 
 	ret = _pglstat64(name, buf);
 
 	/* Do we need to follow a symlink (junction point)? */
-	if (ret == 0 && S_ISLNK(buf->st_mode))
+	while (ret == 0 && S_ISLNK(buf->st_mode))
 	{
 		char		next[MAXPGPATH];
 		ssize_t		size;
 
+		if (++loops > 8)
+		{
+			/*
+			 * Give up. The error for too many symlinks is supposed to be
+			 * ELOOP, but Windows hasn't got it.
+			 */
+			errno = EIO;
+			return -1;
+		}
+
 		/*
 		 * _pglstat64() already called readlink() once to be able to fill in
 		 * st_size, and now we need to do it again to get the path to follow.
@@ -219,17 +230,6 @@ _pgstat64(const char *name, struct stat *buf)
 		next[size] = 0;
 
 		ret = _pglstat64(next, buf);
-		if (ret == 0 && S_ISLNK(buf->st_mode))
-		{
-			/*
-			 * We're only prepared to go one hop, because we only expect to
-			 * deal with the simple cases that we create.  The error for too
-			 * many symlinks is supposed to be ELOOP, but Windows hasn't got
-			 * it.
-			 */
-			errno = EIO;
-			return -1;
-		}
 	}
 
 	return ret;
-- 
2.35.1

--- win32stat.c.bak	2022-08-11 17:15:10.775412600 +0700
+++ win32stat.c	2022-08-11 16:47:41.992805700 +0700
@@ -186,9 +186,12 @@
 {
 	int			loops = 0;
 	int			ret;
+	char		curr[MAXPGPATH];
 
 	ret = _pglstat64(name, buf);
 
+	strlcpy(curr, name, MAXPGPATH);
+
 	/* Do we need to follow a symlink (junction point)? */
 	while (ret == 0 && S_ISLNK(buf->st_mode))
 	{
@@ -211,7 +214,7 @@
 		 * That could be optimized, but stat() on symlinks is probably rare
 		 * and this way is simple.
 		 */
-		size = readlink(name, next, sizeof(next));
+		size = readlink(curr, next, sizeof(next));
 		if (size < 0)
 		{
 			if (errno == EACCES &&
@@ -230,6 +233,7 @@
 		next[size] = 0;
 
 		ret = _pglstat64(next, buf);
+		strcpy(curr, next);
 	}
 
 	return ret;