cmake: Remove broken '--warn-unused-vars' option

This option has been broken since commit b9f9915516 (cmMakefile: Remove
VarUsageStack., 2015-05-17, v3.3.0-rc1~52^2).  That commit removed the
check that an initialized variable has actually been used and caused the
option to warn on every variable ever set.  This was not caught by the
test suite because the test for the feature only checked that warnings
appear when needed and not that they do not appear when not needed.

The option was never very practical to use.  Remove it to avoid the
runtime cost of usage tracking and checks for every variable (which we
were doing even when the option was not used).

1 files changed, 0 insertions, 4 deletions

diff --git a/Source/cmDefinitions.h b/Source/cmDefinitions.h
index 0e38fb1af2..d57750a072 100644
--- a/Source/cmDefinitions.h
+++ b/Source/cmDefinitions.h
@@ -48,9 +48,6 @@ public:
   /** Unset a definition.  */
   void Unset(const std::string& key);
 
-  /** List of unused keys.  */
-  std::vector<std::string> UnusedKeys() const;
-
 private:
   /** String with existence boolean.  */
   struct Def
@@ -62,7 +59,6 @@ private:
     {
     }
     cm::String Value;
-    bool Used = false;
   };
   static Def NoDef;