8273111: Default timezone should return zone ID if /etc/localtime is valid but not canonicalization on linux

Co-authored-by: Sun Jianye <sunjianye@huawei.com>
Reviewed-by: naoto, mli

src/java.base/unix/native/libjava/TimeZone_md.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -38,6 +38,7 @@
 
 #include "jvm.h"
 #include "TimeZone_md.h"
+#include "path_util.h"
 
 static char *isFileIdentical(char* buf, size_t size, char *pathname);
 
@@ -77,6 +78,33 @@ static const char *ETC_ENVIRONMENT_FILE = "/etc/environment";
 
 #if defined(__linux__) || defined(MACOSX)
 
+/*
+ * remove repeated path separators ('/') in the given 'path'.
+ */
+static void
+removeDuplicateSlashes(char *path)
+{
+    char *left = path;
+    char *right = path;
+    char *end = path + strlen(path);
+
+    for (; right < end; right++) {
+        // Skip sequence of multiple path-separators.
+        while (*right == '/' && *(right + 1) == '/') {
+            right++;
+        }
+
+        while (*right != '\0' && !(*right == '/' && *(right + 1) == '/')) {
+            *left++ = *right++;
+        }
+
+        if (*right == '\0') {
+            *left = '\0';
+            break;
+        }
+    }
+}
+
 /*
  * Returns a pointer to the zone ID portion of the given zoneinfo file
  * name, or NULL if the given string doesn't contain "zoneinfo/".
@@ -296,6 +324,8 @@ getPlatformTimeZoneID()
             return NULL;
         }
         linkbuf[len] = '\0';
+        removeDuplicateSlashes(linkbuf);
+        collapse(linkbuf);
         tz = getZoneName(linkbuf);
         if (tz != NULL) {
             tz = strdup(tz);