Make test_util GTest-optional to fix benchmark builds with BUILD_TESTING=OFF When Ceres is configured with BUILD_TESTING=OFF and BUILD_BENCHMARKS=ON, benchmarks failed to compile and link due to an unconditional dependency on the test_util library, which requires Googletest (GTest). This commit addresses the issue by introducing the CERES_HAS_GTEST macro and making the test utility library GTest-optional. Fixes: https://github.com/ceres-solver/ceres-solver/issues/1081 Change-Id: I615c37eb6f21d36a4b87b2d24632016944eda3bd

diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 29c14d1..60200e3 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt

@@ -375,6 +375,7 @@
 
   target_include_directories(test_util PUBLIC ${Ceres_SOURCE_DIR}/internal)
   target_link_libraries (test_util PUBLIC GTest::gmock ceres_static)
+  target_compile_definitions(test_util PUBLIC CERES_HAS_GTEST)
   target_compile_definitions(test_util PRIVATE CERES_TEST_SRCDIR_SUFFIX="../../data")
 
   if (BUILD_SHARED_LIBS)
@@ -526,7 +527,7 @@
   # dependency headers which are not propagated via the ceres targets,
   # so link them explicitly.
   target_link_libraries(${BENCHMARK_TARGET}
-    PRIVATE test_util ceres_static benchmark::benchmark
+    PRIVATE ceres_static benchmark::benchmark
             ${CERES_LIBRARY_PRIVATE_DEPENDENCIES})
 endmacro()
 

diff --git a/internal/ceres/bundle_adjustment_test_util.h b/internal/ceres/bundle_adjustment_test_util.h
index 57f5ab6..4595665 100644
--- a/internal/ceres/bundle_adjustment_test_util.h
+++ b/internal/ceres/bundle_adjustment_test_util.h

@@ -46,8 +46,7 @@
 #include "ceres/test_util.h"
 #include "ceres/types.h"
 
-namespace ceres {
-namespace internal {
+namespace ceres::internal {
 
 const bool kAutomaticOrdering = true;
 const bool kUserOrdering = false;
@@ -62,12 +61,15 @@
     ReadData(input_file);
     BuildProblem();
   }
+
+#ifdef CERES_HAS_GTEST
   BundleAdjustmentProblem() {
     const std::string input_file =
         TestFileAbsolutePath("problem-16-22106-pre.txt");
     ReadData(input_file);
     BuildProblem();
   }
+#endif
 
   ~BundleAdjustmentProblem() {
     delete[] point_index_;
@@ -240,7 +242,8 @@
   double* parameters_;
 };
 
+#ifdef CERES_HAS_GTEST
 using BundleAdjustmentTest = SystemTest<BundleAdjustmentProblem>;
+#endif
 
-}  // namespace internal
-}  // namespace ceres
+}  // namespace ceres::internal

diff --git a/internal/ceres/evaluator_test_utils.cc b/internal/ceres/evaluator_test_utils.cc
index 904635b..91132ad 100644
--- a/internal/ceres/evaluator_test_utils.cc
+++ b/internal/ceres/evaluator_test_utils.cc

@@ -29,6 +29,8 @@
 // Author: keir@google.com (Keir Mierle)
 //         sameeragarwal@google.com (Sameer Agarwal)
 
+#ifdef CERES_HAS_GTEST
+
 #include "ceres/evaluator_test_utils.h"
 
 #include "ceres/internal/eigen.h"
@@ -88,3 +90,5 @@
 }
 
 }  // namespace ceres::internal
+
+#endif  // CERES_HAS_GTEST

diff --git a/internal/ceres/evaluator_test_utils.h b/internal/ceres/evaluator_test_utils.h
index e98dfb6..71d72c2 100644
--- a/internal/ceres/evaluator_test_utils.h
+++ b/internal/ceres/evaluator_test_utils.h

@@ -31,6 +31,8 @@
 //
 // Test utils used for evaluation testing.
 
+#ifdef CERES_HAS_GTEST
+
 #include "ceres/internal/export.h"
 
 namespace ceres::internal {
@@ -58,3 +60,5 @@
                                         const double* actual_jacobian);
 
 }  // namespace ceres::internal
+
+#endif  // CERES_HAS_GTEST

diff --git a/internal/ceres/numeric_diff_test_utils.cc b/internal/ceres/numeric_diff_test_utils.cc
index 0aa1778..4c1b2e2 100644
--- a/internal/ceres/numeric_diff_test_utils.cc
+++ b/internal/ceres/numeric_diff_test_utils.cc

@@ -29,6 +29,8 @@
 // Author: sameeragarwal@google.com (Sameer Agarwal)
 //         tbennun@gmail.com (Tal Ben-Nun)
 
+#ifdef CERES_HAS_GTEST
+
 #include "ceres/numeric_diff_test_utils.h"
 
 #include <algorithm>
@@ -255,3 +257,5 @@
 }
 
 }  // namespace ceres::internal
+
+#endif  // CERES_HAS_GTEST

diff --git a/internal/ceres/numeric_diff_test_utils.h b/internal/ceres/numeric_diff_test_utils.h
index e258ceb..f5f64c7 100644
--- a/internal/ceres/numeric_diff_test_utils.h
+++ b/internal/ceres/numeric_diff_test_utils.h

@@ -28,6 +28,8 @@
 //
 // Author: sameeragarwal@google.com (Sameer Agarwal)
 
+#ifdef CERES_HAS_GTEST
+
 #ifndef CERES_INTERNAL_NUMERIC_DIFF_TEST_UTILS_H_
 #define CERES_INTERNAL_NUMERIC_DIFF_TEST_UTILS_H_
 
@@ -153,3 +155,5 @@
 }  // namespace ceres::internal
 
 #endif  // CERES_INTERNAL_NUMERIC_DIFF_TEST_UTILS_H_
+
+#endif  // CERES_HAS_GTEST

diff --git a/internal/ceres/test_util.cc b/internal/ceres/test_util.cc
index 9ae661e..1805fcd 100644
--- a/internal/ceres/test_util.cc
+++ b/internal/ceres/test_util.cc

@@ -30,6 +30,8 @@
 //
 // Utility functions useful for testing.
 
+#ifdef CERES_HAS_GTEST
+
 #include "ceres/test_util.h"
 
 #include <algorithm>
@@ -43,6 +45,7 @@
 #include "ceres/types.h"
 #include "gtest/gtest.h"
 
+
 // This macro is used to inject additional path information specific
 // to the build system.
 
@@ -139,16 +142,7 @@
   return JoinPath(::testing::SrcDir() + CERES_TEST_SRCDIR_SUFFIX, filename);
 }
 
-std::string ToString(const Solver::Options& options) {
-  return absl::StrFormat(
-      "(%s, %s, %s, %s, %d)",
-      LinearSolverTypeToString(options.linear_solver_type),
-      SparseLinearAlgebraLibraryTypeToString(
-          options.sparse_linear_algebra_library_type),
-      options.linear_solver_ordering ? "USER" : "AUTOMATIC",
-      PreconditionerTypeToString(options.preconditioner_type),
-      options.num_threads);
-}
-
 }  // namespace internal
 }  // namespace ceres
+
+#endif  // CERES_HAS_GTEST

diff --git a/internal/ceres/test_util.h b/internal/ceres/test_util.h
index dcac9a6..1283db4 100644
--- a/internal/ceres/test_util.h
+++ b/internal/ceres/test_util.h

@@ -28,6 +28,8 @@
 //
 // Author: keir@google.com (Keir Mierle)
 
+#ifdef CERES_HAS_GTEST
+
 #ifndef CERES_INTERNAL_TEST_UTIL_H_
 #define CERES_INTERNAL_TEST_UTIL_H_
 
@@ -75,8 +77,6 @@
 // local build/testing environment.
 CERES_NO_EXPORT std::string TestFileAbsolutePath(const std::string& filename);
 
-CERES_NO_EXPORT std::string ToString(const Solver::Options& options);
-
 // A templated test fixture, that is used for testing Ceres end to end
 // by computing a solution to the problem for a given solver
 // configuration and comparing it to a reference solver configuration.
@@ -126,9 +126,12 @@
   std::vector<double> expected_final_residuals_;
 };
 
+
 }  // namespace internal
 }  // namespace ceres
 
 #include "ceres/internal/reenable_warnings.h"
 
 #endif  // CERES_INTERNAL_TEST_UTIL_H_
+
+#endif // CERES_HAS_GTEST