enable visibility control for building on Win32

we still have no functionality on Windows, but at least it compiles

tracetools/CMakeLists.txt

@@ -48,13 +48,18 @@ if(TRACING_ENABLED)
   target_compile_definitions(${PROJECT_NAME} PUBLIC TRACETOOLS_LTTNG_ENABLED)
   target_link_libraries(${PROJECT_NAME} ${LTTNG_LIBRARIES} -ldl)
 endif()
+if(WIN32)
+    # Causes the visibility macros to use dllexport rather than dllimport
+    # which is appropriate when building the dll but not consuming it.
+    target_compile_definitions(${PROJECT_NAME}
+      PRIVATE "TRACETOOLS_BUILDING_DLL")
+endif()
 
 ament_export_interfaces(${PROJECT_NAME}_export HAS_LIBRARY_TARGET)
 
 # Status checking tool
 add_executable(status
   src/status.c
-  src/tracetools.c
   src/utils.cpp
 )
 target_link_libraries(status

tracetools/include/tracetools/tracetools.h

@@ -19,12 +19,13 @@
 #include <string.h>
 #include <stdbool.h>
 #include "tracetools/config.h"
+#include "tracetools/visibility_control.hpp"
 
 #ifndef TRACETOOLS_DISABLED
 #  define TRACEPOINT(event_name, ...) \
   (ros_trace_ ## event_name)(__VA_ARGS__)
 #  define DECLARE_TRACEPOINT(event_name, ...) \
-  void(ros_trace_ ## event_name)(__VA_ARGS__);
+  TRACETOOLS_PUBLIC void(ros_trace_ ## event_name)(__VA_ARGS__);
 #else
 #  define TRACEPOINT(event_name, ...)
 #  define DECLARE_TRACEPOINT(event_name, ...)
@@ -38,7 +39,7 @@ extern "C"
 /**
  * Report whether tracing is compiled in
  */
-bool ros_trace_compile_status();
+TRACETOOLS_PUBLIC bool ros_trace_compile_status();
 
 /**
  * tp: rcl_init

tracetools/include/tracetools/visibility_control.hpp

@@ -0,0 +1,56 @@
+// Copyright 2015 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/* This header must be included by all TRACETOOLS headers which declare symbols
+ * which are defined in the TRACETOOLS library. When not building the TRACETOOLS
+ * library, i.e. when using the headers in other package's code, the contents
+ * of this header change the visibility of certain symbols which the TRACETOOLS
+ * library cannot have, but the consuming code must have inorder to link.
+ */
+
+#ifndef TRACETOOLS__VISIBILITY_CONTROL_HPP_
+#define TRACETOOLS__VISIBILITY_CONTROL_HPP_
+
+// This logic was borrowed (then namespaced) from the examples on the gcc wiki:
+//     https://gcc.gnu.org/wiki/Visibility
+
+#if defined _WIN32 || defined __CYGWIN__
+  #ifdef __GNUC__
+    #define TRACETOOLS_EXPORT __attribute__ ((dllexport))
+    #define TRACETOOLS_IMPORT __attribute__ ((dllimport))
+  #else
+    #define TRACETOOLS_EXPORT __declspec(dllexport)
+    #define TRACETOOLS_IMPORT __declspec(dllimport)
+  #endif
+  #ifdef TRACETOOLS_BUILDING_LIBRARY
+    #define TRACETOOLS_PUBLIC TRACETOOLS_EXPORT
+  #else
+    #define TRACETOOLS_PUBLIC TRACETOOLS_IMPORT
+  #endif
+  #define TRACETOOLS_PUBLIC_TYPE TRACETOOLS_PUBLIC
+  #define TRACETOOLS_LOCAL
+#else
+  #define TRACETOOLS_EXPORT __attribute__ ((visibility("default")))
+  #define TRACETOOLS_IMPORT
+  #if __GNUC__ >= 4
+    #define TRACETOOLS_PUBLIC __attribute__ ((visibility("default")))
+    #define TRACETOOLS_LOCAL  __attribute__ ((visibility("hidden")))
+  #else
+    #define TRACETOOLS_PUBLIC
+    #define TRACETOOLS_LOCAL
+  #endif
+  #define TRACETOOLS_PUBLIC_TYPE
+#endif
+
+#endif  // TRACETOOLS__VISIBILITY_CONTROL_HPP_