From 265c5677573fb5fa260b0368787bb06d224ffb2a Mon Sep 17 00:00:00 2001
From: Edward Diener <eldlistmailingz@tropicsoft.com>
Date: Thu, 15 Aug 2019 02:47:12 -0400
Subject: [PATCH] Make code safer when attempting to use shell fails and there
 are no items.

---
 src/tools/clang-win.jam | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/tools/clang-win.jam b/src/tools/clang-win.jam
index 46885948a..0530543c5 100644
--- a/src/tools/clang-win.jam
+++ b/src/tools/clang-win.jam
@@ -100,22 +100,36 @@ rule init ( version ? : command * : options * )
             }
         }
 
-        local ml = [ regex.replace $(items[1]) "x64\\\\+link\\.exe" "x64\\ml64.exe" ] ;
-        ml = [ regex.replace $(ml) "x86\\\\+link\\.exe" "x86\\ml.exe" ] ;
-
-        if ! [ MATCH "(ml\\.exe)" "(ml64\\.exe)" : $(ml) ]
+        local ml ;
+        
+        if $(items)
         {
-            ml = ;
+            ml = [ regex.replace $(items[1]) "x64\\\\+link\\.exe" "x64\\ml64.exe" ] ;
+            ml = [ regex.replace $(ml) "x86\\\\+link\\.exe" "x86\\ml.exe" ] ;
+
+            if ! [ MATCH "(ml\\.exe)" "(ml64\\.exe)" : $(ml) ]
+            {
+                ml = ;
+            }
         }
 
         local assembler = [ get-option "assembler" : $(addr) : $(options) ] ;
         assembler ?= $(ml) ;
         if $(addr) = 32 { assembler ?= ml.exe ; } else { assembler ?= ml64.exe ; }
 
-        local link = [ regex.replace $(items[1]) "\\\\+HostX64\\\\+x86\\\\+" "\\HostX86\\x86\\" ] ;
+        local link ;
+        
+        if $(items)
+        {
+            link = [ regex.replace $(items[1]) "\\\\+HostX64\\\\+x86\\\\+" "\\HostX86\\x86\\" ] ;
+        }
 
         local archiver = [ get-option "archiver" : $(addr) : $(options) ] ;
-        archiver ?= "$(link) /lib" ;
+        
+        if $(link)
+        {
+            archiver ?= "$(link) /lib" ;
+        }
         archiver ?= lib.exe ;
 
         .notice "$(addr):" "using assembler '$(assembler)'" ;