add logging to integer/linear_programming; keep absl log symbols in libortools, enable GLPK in bazel

examples/cpp/integer_programming.cc

@@ -92,6 +92,7 @@ void RunAllExamples() {
 
 int main(int argc, char** argv) {
   InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_stderrthreshold, 0);
   operations_research::RunAllExamples();
   return EXIT_SUCCESS;
 }

examples/cpp/linear_programming.cc

@@ -122,6 +122,7 @@ void RunAllExamples() {
 
 int main(int argc, char** argv) {
   InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_stderrthreshold, 0);
   operations_research::RunAllExamples();
   return EXIT_SUCCESS;
 }

ortools/base/CMakeLists.txt

@@ -34,6 +34,9 @@ target_include_directories(${NAME} PRIVATE
 target_link_libraries(${NAME} PRIVATE
   ZLIB::ZLIB
   absl::base
+  absl::log
+  absl::log_flags
+  absl::log_initialize
   absl::strings
   absl::str_format
   protobuf::libprotobuf

ortools/base/logging.cc

@@ -36,4 +36,8 @@ void FixFlagsAndEnvironmentForSwig() {
   absl::EnableLogPrefix(false);
 }
 
+void KeepAbslSymbols() {
+  absl::SetFlag(&FLAGS_stderrthreshold, 0);
+}
+
 }  // namespace operations_research

ortools/linear_solver/BUILD.bazel

@@ -113,7 +113,10 @@ cc_library(
         "-DUSE_PDLP",
         "-DUSE_SCIP",
         "-DUSE_HIGHS",
-    ],
+    ] + select({
+        ":with_glpk": ["-DUSE_GLPK"],
+        "//conditions:default": [],
+    }),
     deps = [
         ":linear_solver_cc_proto",
         ":scip_with_glop",
@@ -150,7 +153,8 @@ cc_library(
         "//ortools/util:fp_utils",
         "//ortools/util:lazy_mutable_copy",
     ] + select({
-        ":with_glpk": ["@glpk//:glpk"],
+        ":with_glpk": ["@glpk//:glpk", 
+        "//ortools/glpk:glpk_env_deleter"],
         "//conditions:default": [],
     }),
 )