util.c: let getcwd allocate buffer

* util.c (ruby_getcwd): POSIX.1-2001 extends getcwd(3) as it
  allocates the buffer if the argument is NULL.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45598 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

util.c

@@ -467,19 +467,14 @@ ruby_strdup(const char *str)
     return tmp;
 }
 
-#ifdef __native_client__
 char *
 ruby_getcwd(void)
 {
+#if defined __native_client__
     char *buf = xmalloc(2);
     strcpy(buf, ".");
-    return buf;
-}
-#else
-char *
-ruby_getcwd(void)
-{
-#ifdef HAVE_GETCWD
+#elif defined HAVE_GETCWD
+# if defined NO_GETCWD_MALLOC
     int size = 200;
     char *buf = xmalloc(size);
 
@@ -491,6 +486,12 @@ ruby_getcwd(void)
 	size *= 2;
 	buf = xrealloc(buf, size);
     }
+# else
+    char *buf, *cwd = getcwd(NULL, 0);
+    if (!cwd) rb_sys_fail("getcwd");
+    buf = ruby_strdup(cwd);	/* allocate by xmalloc */
+    free(cwd);
+# endif
 #else
 # ifndef PATH_MAX
 #  define PATH_MAX 8192
@@ -504,7 +505,6 @@ ruby_getcwd(void)
 #endif
     return buf;
 }
-#endif
 
 /****************************************************************
  *