ENH: Improve response to bad if or elseif

Previously bad arguments to an if() or elseif() would cause some
subsequent statements in the corresponding block to execute.  This
teaches CMake to stop processing commands with a fatal error.  It also
provides context to bad elseif() error messages.

Source/cmIfCommand.cxx

@@ -76,6 +76,10 @@ IsFunctionBlocked(const cmListFileFunction& lff,
             }
           else
             {
+            // Place this call on the call stack.
+            cmMakefileCall stack_manager(&mf, this->Functions[c], status);
+            static_cast<void>(stack_manager);
+
             std::string errorString;
             
             std::vector<std::string> expandedArguments;
@@ -98,8 +102,10 @@ IsFunctionBlocked(const cmListFileFunction& lff,
               err += "(";
               err += errorString;
               err += ").";
-              cmSystemTools::Error(err.c_str());
-              return false;
+              mf.IssueMessage(cmake::FATAL_ERROR, err);
+              cmSystemTools::SetFatalErrorOccured();
+              mf.RemoveFunctionBlocker(lff);
+              return true;
               }
         
             if (isTrue)
@@ -204,6 +210,7 @@ bool cmIfCommand
     err += errorString;
     err += ").";
     this->SetError(err.c_str());
+    cmSystemTools::SetFatalErrorOccured();
     return false;
     }
   

Source/cmMakefile.cxx

@@ -348,26 +348,6 @@ bool cmMakefile::GetBacktrace(cmListFileBacktrace& backtrace) const
   return true;
 }
 
-//----------------------------------------------------------------------------
-// Helper class to make sure the call stack is valid.
-class cmMakefileCall
-{
-public:
-  cmMakefileCall(cmMakefile* mf,
-                 cmListFileContext const& lfc,
-                 cmExecutionStatus& status): Makefile(mf)
-    {
-    cmMakefile::CallStackEntry entry = {&lfc, &status};
-    this->Makefile->CallStack.push_back(entry);
-    }
-  ~cmMakefileCall()
-    {
-    this->Makefile->CallStack.pop_back();
-    }
-private:
-  cmMakefile* Makefile;
-};
-
 //----------------------------------------------------------------------------
 bool cmMakefile::ExecuteCommand(const cmListFileFunction& lff,
                                 cmExecutionStatus &status)

Source/cmMakefile.h

@@ -921,5 +921,24 @@ private:
   void EnforceDirectoryLevelRules();
 };
 
+//----------------------------------------------------------------------------
+// Helper class to make sure the call stack is valid.
+class cmMakefileCall
+{
+public:
+  cmMakefileCall(cmMakefile* mf,
+                 cmListFileContext const& lfc,
+                 cmExecutionStatus& status): Makefile(mf)
+    {
+    cmMakefile::CallStackEntry entry = {&lfc, &status};
+    this->Makefile->CallStack.push_back(entry);
+    }
+  ~cmMakefileCall()
+    {
+    this->Makefile->CallStack.pop_back();
+    }
+private:
+  cmMakefile* Makefile;
+};
 
 #endif