From da1c8d360e6b9ba8f1bc291728263548a8e30698 Mon Sep 17 00:00:00 2001
From: Pino Toscano <toscano.pino@tiscali.it>
Date: Sat, 25 Sep 2021 19:10:58 +0200
Subject: [PATCH] Hide most of non-public symbols by default (#984)

* Export YAML::detail::node::m_amount

The internal header node/detail/node.h is included by public headers;
YAML::detail::node is implemented in the header itself, and thus it gets
inlined... except for its static m_amount class member, which is
instantiated in the library only. Right now all the symbols of yaml-cpp
are exported (nothing is hidden), so the linker will find node::m_amount
in the yaml-cpp library.

As solution/workaround, explicitly export YAML::detail::node::m_amount.

* CMake: use GenerateExportHeader

Make use of the GenerateExportHeader CMake module to generate the dll.h
header with export macros.

While the produced dll.h is different, the result should be the same,
i.e. nothing changes for yaml-cpp or its users.

* CMake: hide all the symbols by default

Hide all the symbols that are not explicitly exported with YAML_CPP_API.
This way the ABI will be way smaller, and only actually exposing the
public classes/functions.
---
 CMakeLists.txt         | 15 +++++++++++++++
 include/yaml-cpp/dll.h | 33 ---------------------------------
 src/node_data.cpp      |  2 +-
 3 files changed, 16 insertions(+), 34 deletions(-)
 delete mode 100644 include/yaml-cpp/dll.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b230b9e..73fd8e5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,6 +14,11 @@ include(CMakeDependentOption)
 include(CheckCXXCompilerFlag)
 include(GNUInstallDirs)
 include(CTest)
+include(GenerateExportHeader)
+
+set(CMAKE_C_VISIBILITY_PRESET hidden)
+set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
 
 find_program(YAML_CPP_CLANG_FORMAT_EXE NAMES clang-format)
 
@@ -81,6 +86,7 @@ set_property(TARGET yaml-cpp
 target_include_directories(yaml-cpp
   PUBLIC
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+    $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>
     $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   PRIVATE
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/src>)
@@ -136,6 +142,12 @@ write_basic_package_version_file(
   "${PROJECT_BINARY_DIR}/yaml-cpp-config-version.cmake"
   COMPATIBILITY AnyNewerVersion)
 
+generate_export_header(yaml-cpp
+  BASE_NAME YAML_CPP
+  EXPORT_FILE_NAME "${PROJECT_BINARY_DIR}/include/yaml-cpp/dll.h"
+  EXPORT_MACRO_NAME YAML_CPP_API
+)
+
 configure_file(yaml-cpp.pc.in yaml-cpp.pc @ONLY)
 
 if (YAML_CPP_INSTALL)
@@ -145,6 +157,9 @@ if (YAML_CPP_INSTALL)
     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
     ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 	install(DIRECTORY ${PROJECT_SOURCE_DIR}/include/
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+		FILES_MATCHING PATTERN "*.h")
+	install(DIRECTORY ${PROJECT_BINARY_DIR}/include/
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
 		FILES_MATCHING PATTERN "*.h")
   install(EXPORT yaml-cpp-targets
diff --git a/include/yaml-cpp/dll.h b/include/yaml-cpp/dll.h
deleted file mode 100644
index a32c06b..0000000
--- a/include/yaml-cpp/dll.h
+++ /dev/null
@@ -1,33 +0,0 @@
-#ifndef DLL_H_62B23520_7C8E_11DE_8A39_0800200C9A66
-#define DLL_H_62B23520_7C8E_11DE_8A39_0800200C9A66
-
-#if defined(_MSC_VER) ||                                            \
-    (defined(__GNUC__) && (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || \
-     (__GNUC__ >= 4))  // GCC supports "pragma once" correctly since 3.4
-#pragma once
-#endif
-
-// The following ifdef block is the standard way of creating macros which make
-// exporting from a DLL simpler. All files within this DLL are compiled with the
-// yaml_cpp_EXPORTS symbol defined on the command line. This symbol should not
-// be defined on any project that uses this DLL. This way any other project
-// whose source files include this file see YAML_CPP_API functions as being
-// imported from a DLL, whereas this DLL sees symbols defined with this macro as
-// being exported.
-#undef YAML_CPP_API
-
-#ifdef YAML_CPP_DLL      // Using or Building YAML-CPP DLL (definition defined
-                         // manually)
-#ifdef yaml_cpp_EXPORTS  // Building YAML-CPP DLL (definition created by CMake
-                         // or defined manually)
-//	#pragma message( "Defining YAML_CPP_API for DLL export" )
-#define YAML_CPP_API __declspec(dllexport)
-#else  // yaml_cpp_EXPORTS
-//	#pragma message( "Defining YAML_CPP_API for DLL import" )
-#define YAML_CPP_API __declspec(dllimport)
-#endif  // yaml_cpp_EXPORTS
-#else   // YAML_CPP_DLL
-#define YAML_CPP_API
-#endif  // YAML_CPP_DLL
-
-#endif  // DLL_H_62B23520_7C8E_11DE_8A39_0800200C9A66
diff --git a/src/node_data.cpp b/src/node_data.cpp
index da2aefc..8f5422a 100644
--- a/src/node_data.cpp
+++ b/src/node_data.cpp
@@ -13,7 +13,7 @@
 
 namespace YAML {
 namespace detail {
-std::atomic<size_t> node::m_amount{0};
+YAML_CPP_API std::atomic<size_t> node::m_amount{0};
 
 const std::string& node_data::empty_scalar() {
   static const std::string svalue;