Building with clang and -flto on macOS currently fails with errors
similar to [1]. This is because the --export-dynamic flag is called
-export_dynamic [2] instead and we have not been passing this variant to
the linker, so far.
Attached patch fixes that for configure/make.
CC: Tom, who hit the same in [3] and Andres who last touched
--export-dynamic in 9db49fc5bfdc0126be03f4b8986013e59d93b91d.
Will also create an issue upstream for meson, because the logic is
built-in there.
Would be great if this could be back-patched, since this is the same in
all live versions.
Best,
Wolfgang
[1]: https://postgr.es/m/1581936537572-0.post%40n3.nabble.com
[2]:
https://opensource.apple.com/source/ld64/ld64-609/doc/man/man1/ld.1.auto.html
(grep for export_dynamic)
[3]: https://postgr.es/m/21800.1499270547%40sss.pgh.pa.us
From 55175631d25af11971ec7b7f89d5bf4958ed3c8b Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walt...@technowledgy.de>
Date: Sun, 2 Jun 2024 10:46:56 +0200
Subject: [PATCH v1] Make building with clang's LTO work on macOS
When building with -flto the backend binary must keep many otherwise
unused symbols to make them available to dynamically loaded modules /
extensions. This has been done via -Wl,--export-dynamic on many
platforms for years. This flag is not supported by Apple's clang,
though. Here it's called -Wl,-export_dynamic instead.
Thus, make configure pick up on this variant of the flag as well. Meson
has the logic to detect this flag built-in, but doesn't support this
variant either. This needs to be raised upstream.
Without this fix, building with -flto fails with errors similar to [1]
and [2]. This happens for all currently live versions, including 17 and
HEAD.
[1]: https://postgr.es/m/1581936537572-0.post%40n3.nabble.com
[2]: https://postgr.es/m/21800.1499270547%40sss.pgh.pa.us
---
configure | 39 +++++++++++++++++++++++++++++++++++++++
configure.ac | 2 ++
2 files changed, 41 insertions(+)
diff --git a/configure b/configure
index 7b03db56a67..4c0a1383428 100755
--- a/configure
+++ b/configure
@@ -19135,6 +19135,7 @@ fi
# For linkers that understand --export-dynamic, add that to the LDFLAGS_EX_BE
# (backend specific ldflags). One some platforms this will always fail (e.g.,
# windows), but on others it depends on the choice of linker (e.g., solaris).
+# macos uses -export_dynamic instead.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Wl,--export-dynamic, for LDFLAGS_EX_BE" >&5
$as_echo_n "checking whether $CC supports -Wl,--export-dynamic, for LDFLAGS_EX_BE... " >&6; }
if ${pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl___export_dynamic+:} false; then :
@@ -19173,6 +19174,44 @@ if test x"$pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl___export_dynamic" = x"yes"; then
LDFLAGS_EX_BE="${LDFLAGS_EX_BE} -Wl,--export-dynamic"
fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Wl,-export_dynamic, for LDFLAGS_EX_BE" >&5
+$as_echo_n "checking whether $CC supports -Wl,-export_dynamic, for LDFLAGS_EX_BE... " >&6; }
+if ${pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ pgac_save_LDFLAGS=$LDFLAGS
+LDFLAGS="$pgac_save_LDFLAGS -Wl,-export_dynamic"
+if test "$cross_compiling" = yes; then :
+ pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic="assuming no"
+else
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+extern void $link_test_func (); void (*fptr) () = $link_test_func;
+int
+main ()
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+ pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic=yes
+else
+ pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+ conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+LDFLAGS="$pgac_save_LDFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic" >&5
+$as_echo "$pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic" >&6; }
+if test x"$pgac_cv_prog_cc_LDFLAGS_EX_BE__Wl__export_dynamic" = x"yes"; then
+ LDFLAGS_EX_BE="${LDFLAGS_EX_BE} -Wl,-export_dynamic"
+fi
+
# Create compiler version string
diff --git a/configure.ac b/configure.ac
index 63e7be38472..4f5053fe592 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2423,7 +2423,9 @@ fi
# For linkers that understand --export-dynamic, add that to the LDFLAGS_EX_BE
# (backend specific ldflags). One some platforms this will always fail (e.g.,
# windows), but on others it depends on the choice of linker (e.g., solaris).
+# macos uses -export_dynamic instead.
PGAC_PROG_CC_LD_VARFLAGS_OPT(LDFLAGS_EX_BE, [-Wl,--export-dynamic], $link_test_func)
+PGAC_PROG_CC_LD_VARFLAGS_OPT(LDFLAGS_EX_BE, [-Wl,-export_dynamic], $link_test_func)
AC_SUBST(LDFLAGS_EX_BE)
# Create compiler version string
--
2.45.1
