From 7c3eada02a3a22ff109ef0631e75586308ab2587 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 4 Dec 2017 13:24:37 +0200
Subject: Recognize empty cc.pattern

---
 build2/cc/guess.cxx  | 4 ++--
 build2/cc/guess.hxx  | 6 +++---
 build2/cc/module.cxx | 2 +-
 build2/utility.cxx   | 2 +-
 build2/utility.hxx   | 4 ++--
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/build2/cc/guess.cxx b/build2/cc/guess.cxx
index 627283f..df7899b 100644
--- a/build2/cc/guess.cxx
+++ b/build2/cc/guess.cxx
@@ -1189,7 +1189,7 @@ namespace build2
     }
 
     path
-    guess_default (lang xl, const string& c, const string* pat)
+    guess_default (lang xl, const string& c, const string& pat)
     {
       const char* s (nullptr);
 
@@ -1217,7 +1217,7 @@ namespace build2
         }
       }
 
-      return path (apply_pattern (s, pat));
+      return path (apply_pattern (s, &pat));
     }
   }
 }
diff --git a/build2/cc/guess.hxx b/build2/cc/guess.hxx
index e3a4d8c..86c9793 100644
--- a/build2/cc/guess.hxx
+++ b/build2/cc/guess.hxx
@@ -166,13 +166,13 @@ namespace build2
            const strings* c_coptions,
            const strings* x_coptions);
 
-    // Given a language, toolchain id, and optionally a pattern, return an
-    // appropriate default compiler path.
+    // Given a language, toolchain id, and optionally (empty) a pattern,
+    // return an appropriate default compiler path.
     //
     // For example, for (lang::cxx, gcc, *-4.9) we will get g++-4.9.
     //
     path
-    guess_default (lang, const string& cid, const string* pattern);
+    guess_default (lang, const string& cid, const string& pattern);
   }
 }
 
diff --git a/build2/cc/module.cxx b/build2/cc/module.cxx
index d806583..196c2ce 100644
--- a/build2/cc/module.cxx
+++ b/build2/cc/module.cxx
@@ -88,7 +88,7 @@ namespace build2
         path d (cc_loaded
                 ? guess_default (x_lang,
                                  cast<string> (rs["cc.id"]),
-                                 cast_null<string> (rs["cc.pattern"]))
+                                 cast<string> (rs["cc.pattern"]))
                 : path (x_default));
 
         // If this value was hinted, save it as commented out so that if the
diff --git a/build2/utility.cxx b/build2/utility.cxx
index 36f8a4d..4945514 100644
--- a/build2/utility.cxx
+++ b/build2/utility.cxx
@@ -452,7 +452,7 @@ namespace build2
   string
   apply_pattern (const char* s, const string* p)
   {
-    if (p == nullptr)
+    if (p == nullptr || p->empty ())
       return s;
 
     size_t i (p->find ('*'));
diff --git a/build2/utility.hxx b/build2/utility.hxx
index af26acd..7d1ffc6 100644
--- a/build2/utility.hxx
+++ b/build2/utility.hxx
@@ -469,8 +469,8 @@ namespace build2
                         const cstrings&,
                         bool = false);
 
-  // Apply the specified substitution (stem) to a '*'-pattern. If pattern
-  // is NULL, then return the stem itself. Assume the pattern is valid,
+  // Apply the specified substitution (stem) to a '*'-pattern. If pattern is
+  // NULL or empty, then return the stem itself. Assume the pattern is valid,
   // i.e., contains a single '*' character.
   //
   string
-- 
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