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 ba52ea8e989e9234f38128cf221c68963286fd9e..2f4ae3b53db5a5e4425ee9191db9c95eafa4df16 100644 (file)
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -109,6 +109,7 @@ 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)
@@ -116,19 +117,37 @@ 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 */