LCC: Add policy CMP0129 regarding interpreting LCC as GNU

Due to MCST LCC compiler identification is now changed to LCC,
there should be a way for old projects to still identify it as GNU,
as it was before.
This commits adds the policy:
CMP0129: Compiler id for MCST LCC compilers is now LCC, not GNU.
This policy controls such a behavior.
OLD behaivior is to treat LCC as GNU, NEW is to treat is as LCC.

1 files changed, 48 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index 6dabf63..d5207d8 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -1038,6 +1038,54 @@ void cmGlobalGenerator::CheckCompilerIdCompatibility(
         break;
     }
   }
+
+  if (compilerId == "LCC") {
+    switch (mf->GetPolicyStatus(cmPolicies::CMP0129)) {
+      case cmPolicies::WARN:
+        if (!this->CMakeInstance->GetIsInTryCompile() &&
+            mf->PolicyOptionalWarningEnabled("CMAKE_POLICY_WARNING_CMP0129")) {
+          std::ostringstream w;
+          /* clang-format off */
+          w << cmPolicies::GetPolicyWarning(cmPolicies::CMP0129) << "\n"
+            "Converting " << lang <<
+            R"( compiler id "LCC" to "GNU" for compatibility.)"
+            ;
+          /* clang-format on */
+          mf->IssueMessage(MessageType::AUTHOR_WARNING, w.str());
+        }
+        CM_FALLTHROUGH;
+      case cmPolicies::OLD:
+        // OLD behavior is to convert LCC to GNU.
+        mf->AddDefinition(compilerIdVar, "GNU");
+        if (lang == "C") {
+          mf->AddDefinition("CMAKE_COMPILER_IS_GNUCC", "1");
+        } else if (lang == "CXX") {
+          mf->AddDefinition("CMAKE_COMPILER_IS_GNUCXX", "1");
+        } else if (lang == "Fortran") {
+          mf->AddDefinition("CMAKE_COMPILER_IS_GNUG77", "1");
+        }
+        {
+          // Fix compiler versions.
+          std::string version = "CMAKE_" + lang + "_COMPILER_VERSION";
+          std::string emulated = "CMAKE_" + lang + "_SIMULATE_VERSION";
+          std::string emulatedId = "CMAKE_" + lang + "_SIMULATE_ID";
+          std::string const& actual = mf->GetRequiredDefinition(emulated);
+          mf->AddDefinition(version, actual);
+          mf->RemoveDefinition(emulatedId);
+          mf->RemoveDefinition(emulated);
+        }
+        break;
+      case cmPolicies::REQUIRED_IF_USED:
+      case cmPolicies::REQUIRED_ALWAYS:
+        mf->IssueMessage(
+          MessageType::FATAL_ERROR,
+          cmPolicies::GetRequiredPolicyError(cmPolicies::CMP0129));
+        CM_FALLTHROUGH;
+      case cmPolicies::NEW:
+        // NEW behavior is to keep LCC.
+        break;
+    }
+  }
 }
 
 std::string cmGlobalGenerator::GetLanguageOutputExtension(