From d855b77a80f6f51142ee924b992f2062944ee8e3 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Thu, 21 Nov 2019 17:04:23 -0800
Subject: [PATCH] Check $(version[1]) before using it in [ numbers.less ]
 (#509)

---
 src/tools/common.jam | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/tools/common.jam b/src/tools/common.jam
index 535ef4d21..26a8270e9 100644
--- a/src/tools/common.jam
+++ b/src/tools/common.jam
@@ -974,13 +974,13 @@ local rule toolset-tag ( name : type ? : property-set )
     }
 
     # From GCC 5, versioning changes and minor becomes patch
-    if $(tag) = gcc && [ numbers.less 4 $(version[1]) ]
+    if $(tag) = gcc && $(version[1]) && [ numbers.less 4 $(version[1]) ]
     {
         version = $(version[1]) ;
     }
 
     # Ditto, from Clang 4
-    if ( $(tag) = clang || $(tag) = clangw ) && [ numbers.less 3 $(version[1]) ]
+    if ( $(tag) = clang || $(tag) = clangw ) && $(version[1]) && [ numbers.less 3 $(version[1]) ]
     {
         version = $(version[1]) ;
     }