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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
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‎configure

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Lines changed: 152 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -741,6 +741,8 @@ CPP
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CFLAGS_SL
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BITCODE_CXXFLAGS
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BITCODE_CFLAGS
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CXXFLAGS_SL_MODULE
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CFLAGS_SL_MODULE
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CFLAGS_VECTORIZE
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CFLAGS_UNROLL_LOOPS
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PERMIT_DECLARATION_AFTER_STATEMENT
@@ -6302,6 +6304,154 @@ if test x"$pgac_cv_prog_CC_cflags__ftree_vectorize" = x"yes"; then
63026304
fi
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63046306

6307+
#
6308+
# If the compiler knows how to hide symbols add the switch needed for that
6309+
# to CFLAGS_SL_MODULE and define HAVE_VISIBILITY_ATTRIBUTE.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -fvisibility=hidden, for CFLAGS_SL_MODULE" >&5
6311+
$as_echo_n "checking whether ${CC} supports -fvisibility=hidden, for CFLAGS_SL_MODULE... " >&6; }
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if ${pgac_cv_prog_CC_cflags__fvisibility_hidden+:} false; then :
6313+
$as_echo_n "(cached) " >&6
6314+
else
6315+
pgac_save_CFLAGS=$CFLAGS
6316+
pgac_save_CC=$CC
6317+
CC=${CC}
6318+
CFLAGS="${CFLAGS_SL_MODULE} -fvisibility=hidden"
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ac_save_c_werror_flag=$ac_c_werror_flag
6320+
ac_c_werror_flag=yes
6321+
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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int
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main ()
6326+
{
6327+
6328+
;
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return 0;
6330+
}
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_ACEOF
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if ac_fn_c_try_compile "$LINENO"; then :
6333+
pgac_cv_prog_CC_cflags__fvisibility_hidden=yes
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else
6335+
pgac_cv_prog_CC_cflags__fvisibility_hidden=no
6336+
fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
6338+
ac_c_werror_flag=$ac_save_c_werror_flag
6339+
CFLAGS="$pgac_save_CFLAGS"
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CC="$pgac_save_CC"
6341+
fi
6342+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__fvisibility_hidden" >&5
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$as_echo "$pgac_cv_prog_CC_cflags__fvisibility_hidden" >&6; }
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if test x"$pgac_cv_prog_CC_cflags__fvisibility_hidden" = x"yes"; then
6345+
CFLAGS_SL_MODULE="${CFLAGS_SL_MODULE} -fvisibility=hidden"
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fi
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if test "$pgac_cv_prog_CC_cflags__fvisibility_hidden" = yes; then
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6351+
$as_echo "#define HAVE_VISIBILITY_ATTRIBUTE 1" >>confdefs.h
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fi
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# For C++ we additionally want -fvisibility-inlines-hidden
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -fvisibility=hidden, for CXXFLAGS_SL_MODULE" >&5
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$as_echo_n "checking whether ${CXX} supports -fvisibility=hidden, for CXXFLAGS_SL_MODULE... " >&6; }
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if ${pgac_cv_prog_CXX_cxxflags__fvisibility_hidden+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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pgac_save_CXXFLAGS=$CXXFLAGS
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pgac_save_CXX=$CXX
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CXX=${CXX}
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CXXFLAGS="${CXXFLAGS_SL_MODULE} -fvisibility=hidden"
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ac_save_cxx_werror_flag=$ac_cxx_werror_flag
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ac_cxx_werror_flag=yes
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ac_ext=cpp
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ac_cpp='$CXXCPP $CPPFLAGS'
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ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
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ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
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ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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int
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main ()
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{
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;
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return 0;
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}
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_ACEOF
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if ac_fn_cxx_try_compile "$LINENO"; then :
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pgac_cv_prog_CXX_cxxflags__fvisibility_hidden=yes
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else
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pgac_cv_prog_CXX_cxxflags__fvisibility_hidden=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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ac_ext=c
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ac_cpp='$CPP $CPPFLAGS'
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ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
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ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
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ac_compiler_gnu=$ac_cv_c_compiler_gnu
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ac_cxx_werror_flag=$ac_save_cxx_werror_flag
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CXXFLAGS="$pgac_save_CXXFLAGS"
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CXX="$pgac_save_CXX"
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" >&5
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$as_echo "$pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" >&6; }
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if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_hidden" = x"yes"; then
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CXXFLAGS_SL_MODULE="${CXXFLAGS_SL_MODULE} -fvisibility=hidden"
6403+
fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -fvisibility-inlines-hidden, for CXXFLAGS_SL_MODULE" >&5
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$as_echo_n "checking whether ${CXX} supports -fvisibility-inlines-hidden, for CXXFLAGS_SL_MODULE... " >&6; }
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if ${pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden+:} false; then :
6408+
$as_echo_n "(cached) " >&6
6409+
else
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pgac_save_CXXFLAGS=$CXXFLAGS
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pgac_save_CXX=$CXX
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CXX=${CXX}
6413+
CXXFLAGS="${CXXFLAGS_SL_MODULE} -fvisibility-inlines-hidden"
6414+
ac_save_cxx_werror_flag=$ac_cxx_werror_flag
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ac_cxx_werror_flag=yes
6416+
ac_ext=cpp
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ac_cpp='$CXXCPP $CPPFLAGS'
6418+
ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
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ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
6420+
ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
6423+
/* end confdefs.h. */
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int
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main ()
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{
6428+
6429+
;
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return 0;
6431+
}
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_ACEOF
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if ac_fn_cxx_try_compile "$LINENO"; then :
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pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden=yes
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else
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pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden=no
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fi
6438+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
6439+
ac_ext=c
6440+
ac_cpp='$CPP $CPPFLAGS'
6441+
ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
6442+
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
6443+
ac_compiler_gnu=$ac_cv_c_compiler_gnu
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6445+
ac_cxx_werror_flag=$ac_save_cxx_werror_flag
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CXXFLAGS="$pgac_save_CXXFLAGS"
6447+
CXX="$pgac_save_CXX"
6448+
fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" >&5
6450+
$as_echo "$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" >&6; }
6451+
if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" = x"yes"; then
6452+
CXXFLAGS_SL_MODULE="${CXXFLAGS_SL_MODULE} -fvisibility-inlines-hidden"
6453+
fi
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63056455
#
63066456
# The following tests want to suppress various unhelpful warnings by adding
63076457
# -Wno-foo switches. But gcc won't complain about unrecognized -Wno-foo
@@ -6860,6 +7010,8 @@ fi
68607010

68617011

68627012

7013+
7014+
68637015
# Determine flags used to emit bitcode for JIT inlining.
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# 1. We must duplicate any behaviour-changing compiler flags used above,
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# to keep compatibility with the compiler used for normal Postgres code.

‎configure.ac

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -525,6 +525,17 @@ if test "$GCC" = yes -a "$ICC" = no; then
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# Optimization flags for specific files that benefit from vectorization
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PGAC_PROG_CC_VAR_OPT(CFLAGS_VECTORIZE, [-ftree-vectorize])
527527
#
528+
# If the compiler knows how to hide symbols add the switch needed for that
529+
# to CFLAGS_SL_MODULE and define HAVE_VISIBILITY_ATTRIBUTE.
530+
PGAC_PROG_CC_VAR_OPT(CFLAGS_SL_MODULE, [-fvisibility=hidden])
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if test "$pgac_cv_prog_CC_cflags__fvisibility_hidden" = yes; then
532+
AC_DEFINE([HAVE_VISIBILITY_ATTRIBUTE], 1,
533+
[Define to 1 if your compiler knows the visibility("hidden") attribute.])
534+
fi
535+
# For C++ we additionally want -fvisibility-inlines-hidden
536+
PGAC_PROG_VARCXX_VARFLAGS_OPT(CXX, CXXFLAGS_SL_MODULE, [-fvisibility=hidden])
537+
PGAC_PROG_VARCXX_VARFLAGS_OPT(CXX, CXXFLAGS_SL_MODULE, [-fvisibility-inlines-hidden])
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#
528539
# The following tests want to suppress various unhelpful warnings by adding
529540
# -Wno-foo switches. But gcc won't complain about unrecognized -Wno-foo
530541
# switches, so we have to test for the positive form and if that works,
@@ -573,6 +584,8 @@ fi
573584

574585
AC_SUBST(CFLAGS_UNROLL_LOOPS)
575586
AC_SUBST(CFLAGS_VECTORIZE)
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AC_SUBST(CFLAGS_SL_MODULE)
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AC_SUBST(CXXFLAGS_SL_MODULE)
576589

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# Determine flags used to emit bitcode for JIT inlining.
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# 1. We must duplicate any behaviour-changing compiler flags used above,

‎src/Makefile.global.in

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Original file line numberDiff line numberDiff line change
@@ -258,6 +258,9 @@ SUN_STUDIO_CC = @SUN_STUDIO_CC@
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CXX = @CXX@
259259
CFLAGS = @CFLAGS@
260260
CFLAGS_SL = @CFLAGS_SL@
261+
# *_MODULE are for flags applied to extension libraries
262+
CFLAGS_SL_MODULE = @CFLAGS_SL_MODULE@
263+
CXXFLAGS_SL_MODULE = @CXXFLAGS_SL_MODULE@
261264
CFLAGS_UNROLL_LOOPS = @CFLAGS_UNROLL_LOOPS@
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CFLAGS_VECTORIZE = @CFLAGS_VECTORIZE@
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CFLAGS_SSE42 = @CFLAGS_SSE42@

‎src/Makefile.shlib

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Original file line numberDiff line numberDiff line change
@@ -218,6 +218,19 @@ ifeq ($(PORTNAME), win32)
218218
endif
219219

220220

221+
# If the shared library doesn't have an export file, mark all symbols not
222+
# explicitly exported using PGDLLEXPORT as hidden. We can't pass these flags
223+
# when building a library with explicit exports, as the symbols would be
224+
# hidden before the linker script / exported symbol list takes effect.
225+
#
226+
# This is duplicated in pgxs.mk for MODULES style libraries.
227+
ifeq ($(SHLIB_EXPORTS),)
228+
# LDFLAGS_SL addition not strictly needed, CFLAGS used everywhere, but ...
229+
override LDFLAGS_SL += $(CFLAGS_SL_MODULE)
230+
override CFLAGS += $(CFLAGS_SL_MODULE)
231+
override CXXFLAGS += $(CXXFLAGS_SL_MODULE)
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endif
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221234

222235
##
223236
## BUILD

‎src/include/c.h

Lines changed: 9 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1347,14 +1347,19 @@ extern unsigned long long strtoull(const char *str, char **endptr, int base);
13471347

13481348
/*
13491349
* Use "extern PGDLLEXPORT ..." to declare functions that are defined in
1350-
* loadable modules and need to be callable by the core backend. (Usually,
1351-
* this is not necessary because our build process automatically exports
1352-
* such symbols, but sometimes manual marking is required.)
1353-
* No special marking is required on most ports.
1350+
* loadable modules and need to be callable by the core backend or other
1351+
* loadable modules.
1352+
* If the compiler knows __attribute__((visibility("*"))), we use that,
1353+
* unless we already have a platform-specific definition. Otherwise,
1354+
* no special marking is required.
13541355
*/
13551356
#ifndef PGDLLEXPORT
1357+
#ifdef HAVE_VISIBILITY_ATTRIBUTE
1358+
#define PGDLLEXPORT __attribute__((visibility("default")))
1359+
#else
13561360
#define PGDLLEXPORT
13571361
#endif
1362+
#endif
13581363

13591364
/*
13601365
* The following is used as the arg list for signal handlers. Any ports

‎src/include/pg_config.h.in

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Original file line numberDiff line numberDiff line change
@@ -700,6 +700,9 @@
700700
/* Define to 1 if you have the <uuid/uuid.h> header file. */
701701
#undef HAVE_UUID_UUID_H
702702

703+
/* Define to 1 if your compiler knows the visibility("hidden") attribute. */
704+
#undef HAVE_VISIBILITY_ATTRIBUTE
705+
703706
/* Define to 1 if you have the `wcstombs_l' function. */
704707
#undef HAVE_WCSTOMBS_L
705708

‎src/makefiles/pgxs.mk

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -101,8 +101,11 @@ endif # PGXS
101101

102102
override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
103103

104+
# See equivalent block in Makefile.shlib
104105
ifdef MODULES
105-
override CFLAGS += $(CFLAGS_SL)
106+
override LDFLAGS_SL += $(CFLAGS_SL_MODULE)
107+
override CFLAGS += $(CFLAGS_SL) $(CFLAGS_SL_MODULE)
108+
override CXXFLAGS += $(CFLAGS_SL) $(CXXFLAGS_SL_MODULE)
106109
endif
107110

108111
ifdef MODULEDIR

‎src/tools/msvc/Project.pm

Lines changed: 0 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -419,13 +419,6 @@ sub Save
419419
{
420420
my ($self) = @_;
421421

422-
# If doing DLL and haven't specified a DEF file, do a full export of all symbols
423-
# in the project.
424-
if ($self->{type} eq "dll" && !$self->{def})
425-
{
426-
$self->FullExportDLL($self->{name} . ".lib");
427-
}
428-
429422
# Warning 4197 is about double exporting, disable this per
430423
# http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=99193
431424
$self->DisableLinkerWarnings('4197') if ($self->{platform} eq 'x64');

‎src/tools/msvc/Solution.pm

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -429,6 +429,7 @@ sub GenerateFiles
429429
HAVE_WINLDAP_H => undef,
430430
HAVE_WCSTOMBS_L => 1,
431431
HAVE_WCTYPE_H => 1,
432+
HAVE_VISIBILITY_ATTRIBUTE => undef,
432433
HAVE_WRITEV => undef,
433434
HAVE_X509_GET_SIGNATURE_NID => 1,
434435
HAVE_X86_64_POPCNTQ => undef,

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