Move pg_upgrade's Windows link() implementation to AC_REPLACE_FUNCS

This way we can make use of it in other components as well, and it
fits better with the rest of the build system.

Discussion: https://www.postgresql.org/message-id/flat/72fff73f-dc9c-4ef4-83e8-d2e60c98df48%402ndquadrant.com

configure

@@ -15505,6 +15505,19 @@ esac
 
 fi
 
+ac_fn_c_check_func "$LINENO" "link" "ac_cv_func_link"
+if test "x$ac_cv_func_link" = xyes; then :
+  $as_echo "#define HAVE_LINK 1" >>confdefs.h
+
+else
+  case " $LIBOBJS " in
+  *" link.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS link.$ac_objext"
+ ;;
+esac
+
+fi
+
 ac_fn_c_check_func "$LINENO" "mkdtemp" "ac_cv_func_mkdtemp"
 if test "x$ac_cv_func_mkdtemp" = xyes; then :
   $as_echo "#define HAVE_MKDTEMP 1" >>confdefs.h

configure.in

@@ -1697,6 +1697,7 @@ AC_REPLACE_FUNCS(m4_normalize([
 	getpeereid
 	getrusage
 	inet_aton
+	link
 	mkdtemp
 	pread
 	pwrite

src/bin/pg_upgrade/file.c

@@ -26,10 +26,6 @@
 #include "storage/checksum.h"
 #include "storage/checksum_impl.h"
 
-#ifdef WIN32
-static int	win32_pghardlink(const char *src, const char *dst);
-#endif
-
 
 /*
  * cloneFile()
@@ -151,7 +147,7 @@ void
 linkFile(const char *src, const char *dst,
 		 const char *schemaName, const char *relName)
 {
-	if (pg_link_file(src, dst) < 0)
+	if (link(src, dst) < 0)
 		pg_fatal("error while creating link for relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
 				 schemaName, relName, src, dst, strerror(errno));
 }
@@ -369,29 +365,10 @@ check_hard_link(void)
 	snprintf(new_link_file, sizeof(new_link_file), "%s/PG_VERSION.linktest", new_cluster.pgdata);
 	unlink(new_link_file);		/* might fail */
 
-	if (pg_link_file(existing_file, new_link_file) < 0)
+	if (link(existing_file, new_link_file) < 0)
 		pg_fatal("could not create hard link between old and new data directories: %s\n"
 				 "In link mode the old and new data directories must be on the same file system.\n",
 				 strerror(errno));
 
 	unlink(new_link_file);
 }
-
-#ifdef WIN32
-/* implementation of pg_link_file() on Windows */
-static int
-win32_pghardlink(const char *src, const char *dst)
-{
-	/*
-	 * CreateHardLinkA returns zero for failure
-	 * https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createhardlinka
-	 */
-	if (CreateHardLinkA(dst, src, NULL) == 0)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-	else
-		return 0;
-}
-#endif

src/bin/pg_upgrade/pg_upgrade.h

@@ -65,7 +65,6 @@ extern char *output_files[];
 
 #ifndef WIN32
 #define pg_mv_file			rename
-#define pg_link_file		link
 #define PATH_SEPARATOR		'/'
 #define PATH_QUOTE	'\''
 #define RM_CMD				"rm -f"
@@ -76,7 +75,6 @@ extern char *output_files[];
 #define ECHO_BLANK	""
 #else
 #define pg_mv_file			pgrename
-#define pg_link_file		win32_pghardlink
 #define PATH_SEPARATOR		'\\'
 #define PATH_QUOTE	'"'
 #define RM_CMD				"DEL /q"

src/include/pg_config.h.in

@@ -346,6 +346,9 @@
 /* Define to 1 if you have the `z' library (-lz). */
 #undef HAVE_LIBZ
 
+/* Define to 1 if you have the `link' function. */
+#undef HAVE_LINK
+
 /* Define to 1 if the system has the type `locale_t'. */
 #undef HAVE_LOCALE_T
 

src/include/port.h

@@ -381,6 +381,10 @@ extern float pg_strtof(const char *nptr, char **endptr);
 #define strtof(a,b) (pg_strtof((a),(b)))
 #endif
 
+#ifndef HAVE_LINK
+extern int link(const char *src, const char *dst);
+#endif
+
 #ifndef HAVE_MKDTEMP
 extern char *mkdtemp(char *path);
 #endif

src/port/link.c

@@ -0,0 +1,35 @@
+/*-------------------------------------------------------------------------
+ *
+ * link.c
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/link.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#ifdef WIN32
+
+int
+link(const char *src, const char *dst)
+{
+	/*
+	 * CreateHardLinkA returns zero for failure
+	 * https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createhardlinka
+	 */
+	if (CreateHardLinkA(dst, src, NULL) == 0)
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+	else
+		return 0;
+}
+
+#endif

src/tools/msvc/Mkvcbuild.pm

@@ -98,7 +98,7 @@ sub mkvcbuild
 	  chklocale.c explicit_bzero.c fls.c getpeereid.c getrusage.c inet_aton.c random.c
 	  srandom.c getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
 	  erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
-	  dirent.c dlopen.c getopt.c getopt_long.c
+	  dirent.c dlopen.c getopt.c getopt_long.c link.c
 	  pread.c pwrite.c pg_bitutils.c
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c quotes.c system.c

src/tools/msvc/Solution.pm

@@ -298,6 +298,7 @@ sub GenerateFiles
 		HAVE_LIBXML2                                => undef,
 		HAVE_LIBXSLT                                => undef,
 		HAVE_LIBZ                   => $self->{options}->{zlib} ? 1 : undef,
+		HAVE_LINK                   => undef,
 		HAVE_LOCALE_T               => 1,
 		HAVE_LONG_INT_64            => undef,
 		HAVE_LONG_LONG_INT_64       => 1,