Default to hidden visibility for extension libraries where possible

Until now postgres built extension libraries with global visibility, i.e.
exporting all symbols.  On the one platform where that behavior is not
natively available, namely windows, we emulate it by analyzing the input files
to the shared library and exporting all the symbols therein.

Not exporting all symbols is actually desirable, as it can improve loading
speed, reduces the likelihood of symbol conflicts and can improve intra
extension library function call performance. It also makes the non-windows
builds more similar to windows builds.

Additionally, with meson implementing the export-all-symbols behavior for
windows, turns out to be more verbose than desirable.

This patch adds support for hiding symbols by default and, to counteract that,
explicit symbol visibility annotation for compilers that support
__attribute__((visibility("default"))) and -fvisibility=hidden. That is
expected to be most, if not all, compilers except msvc (for which we already
support explicit symbol export annotations).

Now that extension library symbols are explicitly exported, we don't need to
export all symbols on windows anymore, hence remove that behavior from
src/tools/msvc. The supporting code can't be removed, as we still need to
export all symbols from the main postgres binary.

Author: Andres Freund <andres@anarazel.de>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20211101020311.av6hphdl6xbjbuif@alap3.anarazel.de

1 files changed, 152 insertions, 0 deletions

diff --git a/configure b/configure
index 1e63c6862bc..a4f4d321fb7 100755..100644
--- a/configure
+++ b/configure
@@ -741,6 +741,8 @@ CPP
 CFLAGS_SL
 BITCODE_CXXFLAGS
 BITCODE_CFLAGS
+CXXFLAGS_SL_MODULE
+CFLAGS_SL_MODULE
 CFLAGS_VECTORIZE
 CFLAGS_UNROLL_LOOPS
 PERMIT_DECLARATION_AFTER_STATEMENT
@@ -6303,6 +6305,154 @@ fi
 
 
   #
+  # If the compiler knows how to hide symbols add the switch needed for that
+  # to CFLAGS_SL_MODULE and define HAVE_VISIBILITY_ATTRIBUTE.
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -fvisibility=hidden, for CFLAGS_SL_MODULE" >&5
+$as_echo_n "checking whether ${CC} supports -fvisibility=hidden, for CFLAGS_SL_MODULE... " >&6; }
+if ${pgac_cv_prog_CC_cflags__fvisibility_hidden+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS_SL_MODULE} -fvisibility=hidden"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_CC_cflags__fvisibility_hidden=yes
+else
+  pgac_cv_prog_CC_cflags__fvisibility_hidden=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__fvisibility_hidden" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__fvisibility_hidden" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__fvisibility_hidden" = x"yes"; then
+  CFLAGS_SL_MODULE="${CFLAGS_SL_MODULE} -fvisibility=hidden"
+fi
+
+
+  if test "$pgac_cv_prog_CC_cflags__fvisibility_hidden" = yes; then
+
+$as_echo "#define HAVE_VISIBILITY_ATTRIBUTE 1" >>confdefs.h
+
+  fi
+  # For C++ we additionally want -fvisibility-inlines-hidden
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -fvisibility=hidden, for CXXFLAGS_SL_MODULE" >&5
+$as_echo_n "checking whether ${CXX} supports -fvisibility=hidden, for CXXFLAGS_SL_MODULE... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__fvisibility_hidden+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS_SL_MODULE} -fvisibility=hidden"
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  pgac_cv_prog_CXX_cxxflags__fvisibility_hidden=yes
+else
+  pgac_cv_prog_CXX_cxxflags__fvisibility_hidden=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" = x"yes"; then
+  CXXFLAGS_SL_MODULE="${CXXFLAGS_SL_MODULE} -fvisibility=hidden"
+fi
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -fvisibility-inlines-hidden, for CXXFLAGS_SL_MODULE" >&5
+$as_echo_n "checking whether ${CXX} supports -fvisibility-inlines-hidden, for CXXFLAGS_SL_MODULE... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS_SL_MODULE} -fvisibility-inlines-hidden"
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden=yes
+else
+  pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" = x"yes"; then
+  CXXFLAGS_SL_MODULE="${CXXFLAGS_SL_MODULE} -fvisibility-inlines-hidden"
+fi
+
+  #
   # The following tests want to suppress various unhelpful warnings by adding
   # -Wno-foo switches.  But gcc won't complain about unrecognized -Wno-foo
   # switches, so we have to test for the positive form and if that works,
@@ -6860,6 +7010,8 @@ fi
 
 
 
+
+
 # Determine flags used to emit bitcode for JIT inlining.
 # 1. We must duplicate any behaviour-changing compiler flags used above,
 # to keep compatibility with the compiler used for normal Postgres code.