Avoid using readlink() on platforms that don't support it

We don't have any such platforms now, but might in the future.

Also, detect cases when a tablespace symlink points to a path that
is longer than we can handle, and give a warning.

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index d6ed49a26faa35ea78968375466eec305aa7d5e4..73a7f17149e720c7d6a143f1567ffb859b9be993 100644 (file)
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -108,6 +108,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
                {
                        char            fullpath[MAXPGPATH];
                        char            linkpath[MAXPGPATH];
+                       int                     rllen;
 
                        /* Skip special stuff */
                        if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
@@ -115,19 +116,37 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 
                        snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name);
 
-                       MemSet(linkpath, 0, sizeof(linkpath));
-                       if (readlink(fullpath, linkpath, sizeof(linkpath) - 1) == -1)
+#if defined(HAVE_READLINK) || defined(WIN32)
+                       rllen = readlink(fullpath, linkpath, sizeof(linkpath) - 1);
+                       if (rllen < 0)
+                       {
+                               ereport(WARNING,
+                                               (errmsg("could not read symbolic link \"%s\": %m", fullpath)));
+                               continue;
+                       }
+                       else if (rllen >= sizeof(linkpath))
                        {
                                ereport(WARNING,
-                                 (errmsg("could not read symbolic link \"%s\": %m", fullpath)));
+                                               (errmsg("symbolic link \"%s\" target is too long", fullpath)));
                                continue;
                        }
+                       linkpath[rllen] = '\0';
 
                        ti = palloc(sizeof(tablespaceinfo));
                        ti->oid = pstrdup(de->d_name);
                        ti->path = pstrdup(linkpath);
                        ti->size = opt->progress ? sendDir(linkpath, strlen(linkpath), true) : -1;
                        tablespaces = lappend(tablespaces, ti);
+#else
+                       /*
+                        * If the platform does not have symbolic links, it should not be possible
+                        * to have tablespaces - clearly somebody else created them. Warn about it
+                        * and ignore.
+                        */
+                       ereport(WARNING,
+                                       (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                                        errmsg("tablespaces are not supported on this platform")));
+#endif
                }
 
                /* Add a node for the base directory at the end */