Require CMAKE_<LANG>_COMPILER to be found as a full path

All generators now support detection of the full path to the compiler, so
require it to be so.  This will allow CMake<LANG>Information.cmake and
other logic to assume the full path to the compiler tool is available.

The Makefile generators already rejected CMAKE_<LANG>_COMPILER values
that did not name an existing compiler.  Extend this error message to
all generators, make it occur as early as possible, and improve the
message with advice about how to set the compiler.  If the full path to
the compiler is not known, finish enabling languages with a fatal error
so configuration does not continue.

For now, allow the RC language compiler to not be a full path.  Later we
will need to detect the full path to "rc" under the VS IDE.

Add a RunCMake.CompilerNotFound test to cover failure cases.
Fix the RunCMake.CompilerChange test EmptyCompiler case to work
when configuration does not continue past enable_language.

4 files changed, 99 insertions, 25 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index fb205be..0461001 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -138,15 +138,7 @@ void cmGlobalGenerator::ResolveLanguageCompiler(const std::string &lang,
   if((path.size() == 0 || !cmSystemTools::FileExists(path.c_str()))
       && (optional==false))
     {
-    std::string message = "your ";
-    message += lang;
-    message += " compiler: \"";
-    message +=  name;
-    message += "\" was not found.   Please set ";
-    message += langComp;
-    message += " to a valid compiler path or name.";
-    cmSystemTools::Error(message.c_str());
-    path = name;
+    return;
     }
   std::string doc = lang;
   doc += " compiler.";
@@ -334,7 +326,7 @@ void cmGlobalGenerator::FindMakeProgram(cmMakefile* mf)
 
 void
 cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
-                                  cmMakefile *mf, bool)
+                                  cmMakefile *mf, bool optional)
 {
   if(languages.size() == 0)
     {
@@ -370,6 +362,8 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
       }
     }
 
+  bool fatalError = false;
+
   mf->AddDefinition("RUN_CONFIGURE", true);
   std::string rootBin = mf->GetHomeOutputDirectory();
   rootBin += cmake::GetCMakeFilesDirectory();
@@ -556,6 +550,65 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
       this->SetLanguageEnabled("NONE", mf);
       continue;
       }
+
+    // Check that the compiler was found.
+    std::string compilerName = "CMAKE_";
+    compilerName += lang;
+    compilerName += "_COMPILER";
+    std::string compilerEnv = "CMAKE_";
+    compilerEnv += lang;
+    compilerEnv += "_COMPILER_ENV_VAR";
+    cmOStringStream noCompiler;
+    const char* compilerFile = mf->GetDefinition(compilerName.c_str());
+    if(!compilerFile || !*compilerFile ||
+       cmSystemTools::IsNOTFOUND(compilerFile))
+      {
+      noCompiler <<
+        "No " << compilerName << " could be found.\n"
+        ;
+      }
+    else if(strcmp(lang, "RC") != 0)
+      {
+      if(!cmSystemTools::FileIsFullPath(compilerFile))
+        {
+        noCompiler <<
+          "The " << compilerName << ":\n"
+          "  " << compilerFile << "\n"
+          "is not a full path and was not found in the PATH.\n"
+          ;
+        }
+      else if(!cmSystemTools::FileExists(compilerFile))
+        {
+        noCompiler <<
+          "The " << compilerName << ":\n"
+          "  " << compilerFile << "\n"
+          "is not a full path to an existing compiler tool.\n"
+          ;
+        }
+      }
+    if(!noCompiler.str().empty())
+      {
+      // Skip testing this language since the compiler is not found.
+      needTestLanguage[lang] = false;
+      if(!optional)
+        {
+        // The compiler was not found and it is not optional.  Remove
+        // CMake(LANG)Compiler.cmake so we try again next time CMake runs.
+        std::string compilerLangFile = rootBin;
+        compilerLangFile += "/CMake";
+        compilerLangFile += lang;
+        compilerLangFile += "Compiler.cmake";
+        cmSystemTools::RemoveFile(compilerLangFile.c_str());
+        if(!this->CMakeInstance->GetIsInTryCompile())
+          {
+          this->PrintCompilerAdvice(noCompiler, lang,
+                                    mf->GetDefinition(compilerEnv.c_str()));
+          mf->IssueMessage(cmake::FATAL_ERROR, noCompiler.str());
+          fatalError = true;
+          }
+        }
+      }
+
     std::string langLoadedVar = "CMAKE_";
     langLoadedVar += lang;
     langLoadedVar += "_INFORMATION_LOADED";
@@ -582,26 +635,12 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
       }
     this->LanguagesReady.insert(lang);
 
-    std::string compilerName = "CMAKE_";
-    compilerName += lang;
-    compilerName += "_COMPILER";
-    std::string compilerLangFile = rootBin;
-    compilerLangFile += "/CMake";
-    compilerLangFile += lang;
-    compilerLangFile += "Compiler.cmake";
     // Test the compiler for the language just setup
     // (but only if a compiler has been actually found)
     // At this point we should have enough info for a try compile
     // which is used in the backward stuff
     // If the language is untested then test it now with a try compile.
-    if (!mf->IsSet(compilerName.c_str()))
-      {
-      // if the compiler did not work, then remove the
-      // CMake(LANG)Compiler.cmake file so that it will get tested the
-      // next time cmake is run
-      cmSystemTools::RemoveFile(compilerLangFile.c_str());
-      }
-    else if(needTestLanguage[lang])
+    if(needTestLanguage[lang])
       {
       if (!this->CMakeInstance->GetIsInTryCompile())
         {
@@ -622,6 +661,10 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
         // next time cmake is run
         if(!mf->IsOn(compilerWorks.c_str()))
           {
+          std::string compilerLangFile = rootBin;
+          compilerLangFile += "/CMake";
+          compilerLangFile += lang;
+          compilerLangFile += "Compiler.cmake";
           cmSystemTools::RemoveFile(compilerLangFile.c_str());
           }
         else
@@ -675,6 +718,33 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
     {
     mf->ReadListFile(0,projectCompatibility.c_str());
     }
+
+  if(fatalError)
+    {
+    cmSystemTools::SetFatalErrorOccured();
+    }
+}
+
+//----------------------------------------------------------------------------
+void cmGlobalGenerator::PrintCompilerAdvice(std::ostream& os,
+                                            std::string lang,
+                                            const char* envVar)
+{
+  // Subclasses override this method if they do not support this advice.
+  os <<
+    "Tell CMake where to find the compiler by setting "
+    ;
+  if(envVar)
+    {
+    os <<
+      "either the environment variable \"" << envVar << "\" or "
+      ;
+    }
+  os <<
+    "the CMake cache entry CMAKE_" << lang << "_COMPILER "
+    "to the full path to the compiler, or to the compiler name "
+    "if it is in the PATH."
+    ;
 }
 
 //----------------------------------------------------------------------------
diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index c930b2b..3c4ddb2 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -392,6 +392,8 @@ private:
   void WriteSummary();
   void WriteSummary(cmTarget* target);
 
+  virtual void PrintCompilerAdvice(std::ostream& os, std::string lang,
+                                   const char* envVar);
   void CheckCompilerIdCompatibility(cmMakefile* mf, std::string lang);
 
   cmExternalMakefileProjectGenerator* ExtraGenerator;
diff --git a/Source/cmGlobalVisualStudioGenerator.h b/Source/cmGlobalVisualStudioGenerator.h
index b665158..ce03a0e 100644
--- a/Source/cmGlobalVisualStudioGenerator.h
+++ b/Source/cmGlobalVisualStudioGenerator.h
@@ -107,6 +107,7 @@ protected:
   const char* AdditionalPlatformDefinition;
 
 private:
+  void PrintCompilerAdvice(std::ostream&, std::string, const char*) {}
   void ComputeTargetObjects(cmGeneratorTarget* gt) const;
 
   void FollowLinkDepends(cmTarget* target, std::set<cmTarget*>& linked);
diff --git a/Source/cmGlobalXCodeGenerator.h b/Source/cmGlobalXCodeGenerator.h
index c053943..97072b2 100644
--- a/Source/cmGlobalXCodeGenerator.h
+++ b/Source/cmGlobalXCodeGenerator.h
@@ -210,6 +210,7 @@ protected:
   std::vector<cmXCodeObject*> XCodeObjects;
   cmXCodeObject* RootObject;
 private:
+  void PrintCompilerAdvice(std::ostream&, std::string, const char*) {}
   void ComputeTargetObjects(cmGeneratorTarget* gt) const;
 
   std::string GetObjectsNormalDirectory(