Handle older versions of glog

CMakeLists.txt

@@ -1,6 +1,13 @@
 cmake_minimum_required(VERSION 3.10)
 project(${SKBUILD_PROJECT_NAME} VERSION ${SKBUILD_PROJECT_VERSION})
 
+find_package(glog REQUIRED)
+if(DEFINED glog_VERSION_MAJOR)
+  # Older versions of glog don't export version variables.
+  add_definitions("-DGLOG_VERSION_MAJOR=${glog_VERSION_MAJOR}")
+  add_definitions("-DGLOG_VERSION_MINOR=${glog_VERSION_MINOR}")
+endif()
+
 find_package(Ceres 2.1 REQUIRED)
 
 find_package(Python REQUIRED COMPONENTS Interpreter Development.Module)
@@ -10,9 +17,5 @@ find_package(pybind11 2.11.1 REQUIRED)
 pybind11_add_module(pyceres _pyceres/bindings.cc)
 target_include_directories(pyceres PRIVATE ${PROJECT_SOURCE_DIR})
 target_link_libraries(pyceres PRIVATE glog::glog Ceres::ceres)
-target_compile_definitions(
-  pyceres
-  PRIVATE VERSION_INFO="${PROJECT_VERSION}"
-          GLOG_VERSION_MAJOR=${glog_VERSION_MAJOR}
-          GLOG_VERSION_MINOR=${glog_VERSION_MINOR})
+target_compile_definitions(pyceres PRIVATE VERSION_INFO="${PROJECT_VERSION}")
 install(TARGETS pyceres LIBRARY DESTINATION .)

_pyceres/logging.h

@@ -105,7 +105,8 @@ class LogMessageFatalThrow : public google::LogMessage {
         prefix_(__MakeExceptionPrefix(file, line)){};
   LogMessageFatalThrow(const char* file,
                        int line,
-#if GLOG_VERSION_MAJOR > 0 || GLOG_VERSION_MINOR >= 7
+#if defined(GLOG_VERSION_MAJOR) && \
+    (GLOG_VERSION_MAJOR > 0 || GLOG_VERSION_MINOR >= 7)
                        const google::logging::internal::CheckOpString& result)
 #else
                        const google::CheckOpString& result)
@@ -215,7 +216,8 @@ void BindLogging(py::module& m) {
       .value("ERROR", Logging::LogSeverity::GLOG_ERROR)
       .value("FATAL", Logging::LogSeverity::GLOG_FATAL)
       .export_values();
-#if GLOG_VERSION_MAJOR > 0 || GLOG_VERSION_MINOR >= 6
+#if defined(GLOG_VERSION_MAJOR) && \
+    (GLOG_VERSION_MAJOR > 0 || GLOG_VERSION_MINOR >= 6)
   if (!google::IsGoogleLoggingInitialized())
 #endif
   {