3 files changed, 22 insertions, 2 deletions
diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index 4f3328d..beb10da 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -759,7 +759,8 @@ void cmGlobalGenerator::CheckCompilerIdCompatibility(cmMakefile* mf,
     switch(mf->GetPolicyStatus(cmPolicies::CMP0025))
       {
       case cmPolicies::WARN:
-        if(!this->CMakeInstance->GetIsInTryCompile())
+        if(!this->CMakeInstance->GetIsInTryCompile() &&
+           mf->PolicyOptionalWarningEnabled("CMAKE_POLICY_WARNING_CMP0025"))
           {
           cmOStringStream w;
           w << policies->GetPolicyWarning(cmPolicies::CMP0025) << "\n"
@@ -790,7 +791,8 @@ void cmGlobalGenerator::CheckCompilerIdCompatibility(cmMakefile* mf,
     switch(mf->GetPolicyStatus(cmPolicies::CMP0047))
       {
       case cmPolicies::WARN:
-        if(!this->CMakeInstance->GetIsInTryCompile())
+        if(!this->CMakeInstance->GetIsInTryCompile() &&
+           mf->PolicyOptionalWarningEnabled("CMAKE_POLICY_WARNING_CMP0047"))
           {
           cmOStringStream w;
           w << policies->GetPolicyWarning(cmPolicies::CMP0047) << "\n"
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 10137ec..b195943 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -4350,6 +4350,22 @@ cmMakefile::GetPolicyStatusInternal(cmPolicies::PolicyID id) const
   return this->GetPolicies()->GetPolicyStatus(id);
 }
 
+//----------------------------------------------------------------------------
+bool cmMakefile::PolicyOptionalWarningEnabled(std::string const& var)
+{
+  // Check for an explicit CMAKE_POLICY_WARNING_CMP<NNNN> setting.
+  if(!var.empty())
+    {
+    if(const char* val = this->GetDefinition(var.c_str()))
+      {
+      return cmSystemTools::IsOn(val);
+      }
+    }
+  // Enable optional policy warnings with --debug-output or --trace.
+  cmake* cm = this->GetCMakeInstance();
+  return cm->GetDebugOutput() || cm->GetTrace();
+}
+
 bool cmMakefile::SetPolicy(const char *id,
                            cmPolicies::PolicyStatus status)
 {
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index 45f3b9f..f00fd20 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -875,6 +875,8 @@ public:
   std::set<cmStdString> const & GetSystemIncludeDirectories() const
     { return this->SystemIncludeDirectories; }
 
+  bool PolicyOptionalWarningEnabled(std::string const& var);
+
 protected:
   // add link libraries and directories to the target
   void AddGlobalLinkInformation(const char* name, cmTarget& target);