random.c: fix failures on old Linux

This follows the behavior of fill_random_bytes_urandom and fixes
the following failures I encountered on my old machine:

1) Error:
TestSecureRandom#test_s_random_bytes_without_openssl:
NotImplementedError: No random device
    $RUBYDIR/lib/securerandom.rb:66:in `gen_random'
    $RUBYDIR/lib/securerandom.rb:94:in `random_bytes'
    $RUBYDIR/test/test_securerandom.rb:12:in `test_s_random_bytes'
    $RUBYDIR/test/test_securerandom.rb:97:in `block in test_s_random_bytes_without_openssl'
    $RUBYDIR/lib/tmpdir.rb:88:in `mktmpdir'
    $RUBYDIR/test/test_securerandom.rb:85:in `test_s_random_bytes_without_openssl'

  2) Error:
TestSecureRandom#test_s_urlsafe_base64:
NotImplementedError: No random device
    $RUBYDIR/lib/securerandom.rb:66:in `gen_random'
    $RUBYDIR/lib/securerandom.rb:94:in `random_bytes'
    $RUBYDIR/lib/securerandom.rb:164:in `urlsafe_base64'
    $RUBYDIR/test/test_securerandom.rb:131:in `block in test_s_urlsafe_base64'
    $RUBYDIR/test/test_securerandom.rb:130:in `times'
    $RUBYDIR/test/test_securerandom.rb:130:in `test_s_urlsafe_base64'

  3) Error:
TestSecureRandom#test_uuid:
NotImplementedError: No random device
    $RUBYDIR/lib/securerandom.rb:66:in `gen_random'
    $RUBYDIR/lib/securerandom.rb:94:in `random_bytes'
    $RUBYDIR/lib/securerandom.rb:230:in `uuid'
    $RUBYDIR/test/test_securerandom.rb:160:in `test_uuid'

* random.c (fill_random_bytes_syscall): return -1 for error
* random.c (fill_random_bytes): try urandom on syscall failure

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51183 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Tue Jul  7 16:39:04 2015  Eric Wong  <e@80x24.org>
+
+	* random.c (fill_random_bytes_syscall): return -1 for error
+	* random.c (fill_random_bytes): try urandom on syscall failure
+
 Tue Jul  7 15:02:18 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* file.c (rb_str_normalize_ospath): skip invalid byte sequence not

random.c

@@ -529,7 +529,7 @@ fill_random_bytes_syscall(void *seed, size_t size)
 	    }
 	if ((size_t)ret == size) return 0;
     }
-    return 0;
+    return -1;
 }
 #else
 # define fill_random_bytes_syscall(seed, size) -1
@@ -539,7 +539,7 @@ static int
 fill_random_bytes(void *seed, size_t size)
 {
     int ret = fill_random_bytes_syscall(seed, size);
-    if (ret) return ret;
+    if (ret == 0) return ret;
     return fill_random_bytes_urandom(seed, size);
 }