[Cmake-commits] CMake branch, next, updated. v3.5.0-639-gf6693dc

[Brad King]

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- Log -----------------------------------------------------------------
https://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=f6693dca380152ff9bfd2e06daf800de9edf95b1
commit f6693dca380152ff9bfd2e06daf800de9edf95b1
Merge: 7be32f8 c610402
Author:     Brad King <brad.king at kitware.com>
AuthorDate: Wed Mar 23 16:17:58 2016 -0400
Commit:     CMake Topic Stage <kwrobot at kitware.com>
CommitDate: Wed Mar 23 16:17:58 2016 -0400

    Merge topic 'fix-variable_watch-reallocation' into next
    
    c6104028 Avoid occasional use-after-free when a variable watch is executed


https://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=c61040282557ba268e144ffa5e2d1935b5991d8d
commit c61040282557ba268e144ffa5e2d1935b5991d8d
Author:     Yves Frederix <yves.frederix at gmail.com>
AuthorDate: Wed Mar 23 10:37:51 2016 +0100
Commit:     Brad King <brad.king at kitware.com>
CommitDate: Wed Mar 23 16:17:36 2016 -0400

    Avoid occasional use-after-free when a variable watch is executed
    
    Re-lookup a variable value when an associated VariableWatch is executed
    in cmMakefile::GetDefinition.
    
    This fixes a problem with 'def' sometimes becoming invalid due to memory
    reallocation inside an std::vector. In this case, the problem was that
    if the call to VariableAccessed actually executed a callback function,
    the internal state of the makefile has changed due to the associated
    function scope being pushed. This in turn implies that a new
    cmDefinitions instance was pushed in cmMakefile::VarTree. As
    cmLinkedTree is based on an std::vector, this push can have triggered
    reallocation of its internal memory buffer. However, as the value of
    'def', which was computed on method entry, actually points to a property
    of one of the cmDefinitions instances in cmMakefile::VarTree,
    reallocation can invalidate the value of 'def' so that it cannot simply
    be returned at the end of the function. The solution implemented here is
    to simply lookup the value of 'def' again.

diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 950b247..600c985 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -2531,15 +2531,22 @@ const char* cmMakefile::GetDefinition(const std::string& name) const
   cmVariableWatch* vv = this->GetVariableWatch();
   if ( vv && !this->SuppressWatches )
     {
-    if ( def )
-      {
-      vv->VariableAccessed(name, cmVariableWatch::VARIABLE_READ_ACCESS,
-        def, this);
-      }
-    else
-      {
+    bool const watch_function_executed =
       vv->VariableAccessed(name,
-          cmVariableWatch::UNKNOWN_VARIABLE_READ_ACCESS, def, this);
+                           def ? cmVariableWatch::VARIABLE_READ_ACCESS
+                           : cmVariableWatch::UNKNOWN_VARIABLE_READ_ACCESS,
+                           def, this);
+
+    if (watch_function_executed)
+      {
+      // A callback was executed and may have caused re-allocation of the
+      // variable storage.  Look it up again for now.
+      // FIXME: Refactor variable storage to avoid this problem.
+      def = this->StateSnapshot.GetDefinition(name);
+      if(!def)
+        {
+        def = this->GetState()->GetInitializedCacheValue(name);
+        }
       }
     }
 #endif
diff --git a/Source/cmVariableWatch.cxx b/Source/cmVariableWatch.cxx
index 57dde31..a200718 100644
--- a/Source/cmVariableWatch.cxx
+++ b/Source/cmVariableWatch.cxx
@@ -96,7 +96,7 @@ void cmVariableWatch::RemoveWatch(const std::string& variable,
     }
 }
 
-void  cmVariableWatch::VariableAccessed(const std::string& variable,
+bool  cmVariableWatch::VariableAccessed(const std::string& variable,
                                         int access_type,
                                         const char* newValue,
                                         const cmMakefile* mf) const
@@ -112,5 +112,7 @@ void  cmVariableWatch::VariableAccessed(const std::string& variable,
       (*it)->Method(variable, access_type, (*it)->ClientData,
         newValue, mf);
       }
+    return true;
     }
+  return false;
 }
diff --git a/Source/cmVariableWatch.h b/Source/cmVariableWatch.h
index 0ca4a55..2f082af 100644
--- a/Source/cmVariableWatch.h
+++ b/Source/cmVariableWatch.h
@@ -42,7 +42,7 @@ public:
   /**
    * This method is called when variable is accessed
    */
-  void VariableAccessed(const std::string& variable, int access_type,
+  bool VariableAccessed(const std::string& variable, int access_type,
     const char* newValue, const cmMakefile* mf) const;
 
   /**

-----------------------------------------------------------------------

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