fix absl flags decldll on windows

Author: Mizux

examples/cpp/nqueens.cc

@@ -39,7 +39,6 @@ ABSL_FLAG(
     int, size, 0,
     "Size of the problem. If equal to 0, will test several increasing sizes.");
 ABSL_FLAG(bool, use_symmetry, false, "Use Symmetry Breaking methods");
-ABSL_DECLARE_FLAG(bool, cp_disable_solve);
 
 static const int kNumSolutions[] = {
     1, 0, 0, 2, 10, 4, 40, 92, 352, 724, 2680, 14200, 73712, 365596, 2279184};

ortools/base/macros.h

@@ -16,10 +16,23 @@
 
 #include <cstdlib>  // for size_t.
 
+#include "absl/flags/declare.h"
 #include "ortools/base/base_export.h" // for OR_DLL
 
 #define COMPILE_ASSERT(x, msg)
 
+// The ABSL_DECLARE_DLL_FLAG(dll, type, name) macro expands to:
+//   dll extern absl::Flag<type> FLAGS_name;
+#define ABSL_DECLARE_DLL_FLAG(dll, type, name) ABSL_DECLARE_DLL_FLAG_INTERNAL(dll, type, name)
+
+// Internal implementation of ABSL_DECLARE_FLAG to allow macro expansion of its
+// arguments. Clients must use ABSL_DECLARE_FLAG instead.
+#define ABSL_DECLARE_DLL_FLAG_INTERNAL(dll, type, name)      \
+  dll extern absl::Flag<type> FLAGS_##name;                  \
+  namespace absl /* block flags in namespaces */ {}          \
+  /* second redeclaration is to allow applying attributes */ \
+  dll extern absl::Flag<type> FLAGS_##name
+
 #ifdef NDEBUG
 const bool DEBUG_MODE = false;
 #else   // NDEBUG

ortools/constraint_solver/constraint_solver.h

@@ -104,7 +104,8 @@
 #include "ortools/util/tuple_set.h"
 
 #if !defined(SWIG)
-ABSL_DECLARE_FLAG(int64_t, cp_random_seed);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, int64_t, cp_random_seed);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, bool, cp_disable_solve);
 #endif  // !defined(SWIG)
 
 class File;

ortools/graph/CMakeLists.txt

@@ -26,6 +26,10 @@ add_library(${NAME} OBJECT ${_SRCS})
 set_target_properties(${NAME} PROPERTIES
   POSITION_INDEPENDENT_CODE ON
   )
+if(MSVC AND BUILD_SHARED_LIBS)
+  target_compile_definitions(${NAME} PUBLIC "OR_BUILD_DLL")
+  target_compile_definitions(${NAME} PRIVATE "OR_EXPORT")
+endif()
 target_include_directories(${NAME} PRIVATE
   ${PROJECT_SOURCE_DIR}
   ${PROJECT_BINARY_DIR})

ortools/graph/linear_assignment.h

@@ -214,9 +214,9 @@
 #include "ortools/util/zvector.h"
 
 #ifndef SWIG
-ABSL_DECLARE_FLAG(int64_t, assignment_alpha);
-ABSL_DECLARE_FLAG(int, assignment_progress_logging_period);
-ABSL_DECLARE_FLAG(bool, assignment_stack_order);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, int64_t, assignment_alpha);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, int, assignment_progress_logging_period);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, bool, assignment_stack_order);
 #endif
 
 namespace operations_research {

ortools/graph/linear_assignment_test.cc

@@ -29,8 +29,6 @@
 #include "ortools/base/gmock.h"
 #include "ortools/graph/graph.h"
 
-ABSL_DECLARE_FLAG(bool, assignment_stack_order);
-
 namespace operations_research {
 
 using ::testing::Eq;

ortools/util/time_limit.h

@@ -38,7 +38,7 @@
  * Enables changing the behavior of the TimeLimit class to use -b usertime
  * instead of \b walltime. This is mainly useful for benchmarks.
  */
-ABSL_DECLARE_FLAG(bool, time_limit_use_usertime);
+ABSL_DECLARE_DLL_FLAG(OR_DLL, bool, time_limit_use_usertime);
 
 namespace operations_research {