Function GetWindowsValue

Source/cmCMakeHostSystemInformationCommand.cxx:560–610

}

cm::optional<std::string> GetWindowsValue(cmExecutionStatus& status,
                                          std::string const& key)
{
  auto* const gg = status.GetMakefile().GetGlobalGenerator();
  for (auto vs : { 15, 16, 17, 18 }) {
    if (key == cmStrCat("VS_"_s, vs, "_DIR"_s)) {
      std::string value;
      // If generating for the VS nn IDE, use the same instance.

      if (cmHasPrefix(gg->GetName(), cmStrCat("Visual Studio "_s, vs, ' '))) {
        cmGlobalVisualStudioVersionedGenerator* vsNNgen =
          static_cast<cmGlobalVisualStudioVersionedGenerator*>(gg);
        if (vsNNgen->GetVSInstance(value)) {
          return value;
        }
      }

      // Otherwise, find a VS nn instance ourselves.
      cmVSSetupAPIHelper vsSetupAPIHelper(vs);
      if (vsSetupAPIHelper.GetVSInstanceInfo(value)) {
        cmSystemTools::ConvertToUnixSlashes(value);
      }
      return value;
    }
  }

  if (key == "VS_MSBUILD_COMMAND"_s && gg->IsVisualStudioAtLeast10()) {
    cmGlobalVisualStudio10Generator* vs10gen =
      static_cast<cmGlobalVisualStudio10Generator*>(gg);
    return vs10gen->FindMSBuildCommandEarly(&status.GetMakefile());
  }

  if (key == "MSYSTEM_PREFIX") {
    // MSYSTEM_PREFIX is meaningful only under a MSYSTEM environment.
    cm::optional<std::string> ms = cmSystemTools::GetEnvVar("MSYSTEM");
    if (!ms || ms->empty()) {
      return std::string();
    }
    // Prefer the MSYSTEM_PREFIX environment variable.
    if (cm::optional<std::string> msp =
          cmSystemTools::GetEnvVar("MSYSTEM_PREFIX")) {
      cmSystemTools::ConvertToUnixSlashes(*msp);
      if (cmSystemTools::FileIsDirectory(*msp)) {
        return msp;
      }
    }
    // Fall back to known distribution layouts.
    return FallbackMSYSTEM_PREFIX(*ms);
  }
  return {};
}
#endif

cm::optional<std::string> GetValueChained()