From 13d165de9e737cec750a2ab3d1ef68bb3f276c48 Mon Sep 17 00:00:00 2001
From: Alexandros Frantzis <alexandros.frantzis@canonical.com>
Date: Fri, 10 Mar 2017 14:25:27 +0200
Subject: [PATCH] Hide unnecessary exported library symbols

---
 configure.ac             | 19 +++++++++++++++++++
 src/Makefile.am          | 15 +++++++++++++++
 src/libprotobuf-lite.map |  9 +++++++++
 src/libprotobuf.map      |  9 +++++++++
 src/libprotoc.map        |  9 +++++++++
 5 files changed, 61 insertions(+)
 create mode 100644 src/libprotobuf-lite.map
 create mode 100644 src/libprotobuf.map
 create mode 100644 src/libprotoc.map

diff --git a/configure.ac b/configure.ac
index 6d9c2a017a..531e25fbc8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -93,6 +93,25 @@ ACX_CHECK_SUNCC
 # to the link
 AC_PROG_LIBTOOL
 
+# Check whether the linker supports version scripts
+AC_MSG_CHECKING([whether the linker supports version scripts])
+save_LDFLAGS=$LDFLAGS
+LDFLAGS="$LDFLAGS -Wl,--version-script=conftest.map"
+cat > conftest.map <<EOF
+{
+  global:
+    main;
+  local:
+    *;
+};
+EOF
+AC_LINK_IFELSE(
+  [AC_LANG_SOURCE([int main() { return 0; }])],
+  [have_ld_version_script=yes; AC_MSG_RESULT(yes)],
+  [have_ld_version_script=no; AC_MSG_RESULT(no)])
+LDFLAGS=$save_LDFLAGS
+AM_CONDITIONAL([HAVE_LD_VERSION_SCRIPT], [test "$have_ld_version_script" == "yes"])
+
 # Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS([fcntl.h inttypes.h limits.h stdlib.h unistd.h])
diff --git a/src/Makefile.am b/src/Makefile.am
index 8c25a10a1d..6a91044da0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -180,6 +180,10 @@ lib_LTLIBRARIES = libprotobuf-lite.la libprotobuf.la libprotoc.la
 
 libprotobuf_lite_la_LIBADD = $(PTHREAD_LIBS)
 libprotobuf_lite_la_LDFLAGS = -version-info 12:0:0 -export-dynamic -no-undefined
+if HAVE_LD_VERSION_SCRIPT
+libprotobuf_lite_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotobuf-lite.map
+EXTRA_libprotobuf_lite_la_DEPENDENCIES = libprotobuf-lite.map
+endif
 libprotobuf_lite_la_SOURCES =                                  \
   google/protobuf/stubs/atomicops_internals_x86_gcc.cc         \
   google/protobuf/stubs/atomicops_internals_x86_msvc.cc        \
@@ -221,6 +225,10 @@ libprotobuf_lite_la_SOURCES =                                  \
 
 libprotobuf_la_LIBADD = $(PTHREAD_LIBS)
 libprotobuf_la_LDFLAGS = -version-info 12:0:0 -export-dynamic -no-undefined
+if HAVE_LD_VERSION_SCRIPT
+libprotobuf_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotobuf.map
+EXTRA_libprotobuf_la_DEPENDENCIES = libprotobuf.map
+endif
 libprotobuf_la_SOURCES =                                       \
   $(libprotobuf_lite_la_SOURCES)                               \
   google/protobuf/any.pb.cc                                    \
@@ -305,6 +313,10 @@ nodist_libprotobuf_la_SOURCES = $(nodist_libprotobuf_lite_la_SOURCES)
 
 libprotoc_la_LIBADD = $(PTHREAD_LIBS) libprotobuf.la
 libprotoc_la_LDFLAGS = -version-info 12:0:0 -export-dynamic -no-undefined
+if HAVE_LD_VERSION_SCRIPT
+libprotoc_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotoc.map
+EXTRA_libprotoc_la_DEPENDENCIES = libprotoc.map
+endif
 libprotoc_la_SOURCES =                                         \
   google/protobuf/compiler/code_generator.cc                   \
   google/protobuf/compiler/command_line_interface.cc           \
@@ -580,6 +592,9 @@ EXTRA_DIST =                                                   \
   google/protobuf/compiler/ruby/ruby_generated_code_pb.rb      \
   google/protobuf/compiler/package_info.h                      \
   google/protobuf/compiler/zip_output_unittest.sh              \
+  libprotobuf-lite.map                                         \
+  libprotobuf.map                                              \
+  libprotoc.map                                                \
   README.md
 
 protoc_lite_outputs =                                          \
diff --git a/src/libprotobuf-lite.map b/src/libprotobuf-lite.map
new file mode 100644
index 0000000000..3915546694
--- /dev/null
+++ b/src/libprotobuf-lite.map
@@ -0,0 +1,9 @@
+{
+  global:
+    extern "C++" {
+      *google*;
+    };
+
+  local:
+    *;
+};
diff --git a/src/libprotobuf.map b/src/libprotobuf.map
new file mode 100644
index 0000000000..3915546694
--- /dev/null
+++ b/src/libprotobuf.map
@@ -0,0 +1,9 @@
+{
+  global:
+    extern "C++" {
+      *google*;
+    };
+
+  local:
+    *;
+};
diff --git a/src/libprotoc.map b/src/libprotoc.map
new file mode 100644
index 0000000000..3915546694
--- /dev/null
+++ b/src/libprotoc.map
@@ -0,0 +1,9 @@
+{
+  global:
+    extern "C++" {
+      *google*;
+    };
+
+  local:
+    *;
+};