Use visibility hidden by default (#392)

* Use visibility hidden by default The commit changes the gz-cmake projects to use C/C++ visibility hidden by default. This is a potential breaking changed for projects using gz-cmake but the benefits in terms of creating portable code and time spend by the loader could be huge. To avoid this change, the EXPOSE_SYMBOLS_BY_DEFAULT flag can be used in the gz_configure_project call. The change deprecates the HIDDEN_SYMBOLS_BY_DEFAULT flag. --------- Signed-off-by: Jose Luis Rivero <[email protected]> Co-authored-by: Michael Carroll <[email protected]> Co-authored-by: Addisu Z. Taddese <[email protected]>
gazebosim · Jan 26, 2024 · 646292a · 646292a
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diff --git a/Migration.md b/Migration.md
@@ -9,6 +9,17 @@ release will remove the deprecated code.
 
 1. The minimum required cmake version is now 3.22.1.
 
+1. **Breaking**: C/C++ projects enable the `visibility=hidden` compiler flag by default.
+   gz-cmake4 changes gz-cmake projects to use C/C++ visibility hidden
+   by default. This is a potential breaking changed for projects using
+   gz-cmake but the benefits in terms of creating portable code and
+   time spend by the loader could be relevant.
+   To avoid this change, the EXPOSE_SYMBOLS_BY_DEFAULT flag can be used in
+   the gz_configure_project call.
+   The change deprecates the HIDDEN_SYMBOLS_BY_DEFAULT flag that can be
+   removed.
+
+
 ## Gazebo CMake 2.X to 3.X
 
 1. **Breaking**: Examples are now built using native cmake.

diff --git a/cmake/GzConfigureBuild.cmake b/cmake/GzConfigureBuild.cmake
@@ -24,16 +24,22 @@
 #################################################
 # Configure the build of the Gazebo project
 # Pass the argument HIDE_SYMBOLS_BY_DEFAULT to configure symbol visibility so
-# that symbols are hidden unless explicitly marked as visible.
+# that symbols are hidden unless explicitly marked as visible. (DEPRECATED)
+# Pass the argument EXPOSE_SYMBOLS_BY_DEFAULT to configure symbol visibility
+# so symbols are exposed unless explicitly marked as hidden.
 # Pass the argument QUIT_IF_BUILD_ERRORS to have this macro quit cmake when the
 # build_errors
 macro(gz_configure_build)
   # Parse the arguments that are passed in
-  set(options HIDE_SYMBOLS_BY_DEFAULT QUIT_IF_BUILD_ERRORS)
+  set(options HIDE_SYMBOLS_BY_DEFAULT EXPOSE_SYMBOLS_BY_DEFAULT QUIT_IF_BUILD_ERRORS)
   set(oneValueArgs)
   set(multiValueArgs COMPONENTS)
   cmake_parse_arguments(gz_configure_build "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
+  if(gz_configure_build_HIDE_SYMBOLS_BY_DEFAULT)
+    message(DEPRECATION "HIDE_SYMBOLS_BY_DEFAULT is now the default. You can safely remove the option.")
+  endif()
+
   #============================================================================
   # Examine the build type. If we do not recognize the type, we will generate
   # an error, so this must come before the error handling.

diff --git a/cmake/GzSetCompilerFlags.cmake b/cmake/GzSetCompilerFlags.cmake
@@ -113,12 +113,12 @@ endmacro()
 # Internal to gz-cmake.
 macro(_gz_setup_gcc_or_clang)
 
-  if(gz_configure_build_HIDE_SYMBOLS_BY_DEFAULT)
-    set(CMAKE_C_VISIBILITY_PRESET "hidden")
-    set(CMAKE_CXX_VISIBILITY_PRESET "hidden")
-  else()
+  if(gz_configure_build_EXPOSE_SYMBOLS_BY_DEFAULT)
     set(CMAKE_C_VISIBILITY_PRESET "default")
     set(CMAKE_CXX_VISIBILITY_PRESET "default")
+  else()
+    set(CMAKE_C_VISIBILITY_PRESET "hidden")
+    set(CMAKE_CXX_VISIBILITY_PRESET "hidden")
   endif()