Re: [PATCH] Ada, Darwin: Do not link libgcc statically on Darwin [PR108202].

[Iain Sandoe <iain@sandoe.co.uk>]

I would like to revise this patch to be more conservative (only applying to Darwin 8 and 9).

> On 24 Dec 2022, at 19:00, Iain Sandoe via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> Tested on i686, x86-64 darwin, x86_64-linux (with a 32b multilib).
> OK for trunk?
> Iain

revised:

[PATCH] Ada,Darwin: Do not link libgcc statically on Darwin 8 and 9  [PR108202].

Normally, GCC executables are built with -static-libstdc++ -static-libgcc
on Darwin.  This is fine in most cases, because GCC executables typically
do not use exceptions.   However gnat1 does use exceptions and also pulls
in system libraries that are linked against the installed shared libgcc
which contains the system unwinder.  This means that gnat1 effectively has
two unwinder instances (which does not work reliably since the unwinders
have global state).

A recent change in the initialization of FDEs has made this a hard error
now on Darwin versions (8 and 9) with libgcc installed in /usr/lib (gnat1
now hangs when an exception is thrown).

The solution is to link libgcc dynamically, picking up the installed
system version.  To do this we strip -static-libgcc from the link flags.

	PR ada/108202

gcc/ada/ChangeLog:

	* gcc-interface/Make-lang.in (GCC_LINKERFLAGS, GCC_LDFLAGS):
	Versions of ALL_LINKERFLAGS, LDFLAGS with -Werror and
	-static-libgcc filtered out for Darwin8 and 9 (-Werror is filtered
	out for other hosts).
---
 gcc/ada/gcc-interface/Make-lang.in | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/gcc-interface/Make-lang.in b/gcc/ada/gcc-interface/Make-lang.in
index 2acd195017e..c81daae9c4a 100644
--- a/gcc/ada/gcc-interface/Make-lang.in
+++ b/gcc/ada/gcc-interface/Make-lang.in
@@ -260,11 +260,20 @@ else
   endif
 endif
 
+ifneq ($(filter darwin9% darwin8%,$(host_os)),)
+# gnat1 uses exceptions which is incompatible with statically-linked libgcc
+# on Darwin8 and 9, since gnat1 also pulls in libraries linked with the system
+# unwinder.
+GCC_LINKERFLAGS = $(filter-out -Werror -static-libgcc, $(ALL_LINKERFLAGS))
+GCC_LDFLAGS = $(filter-out -static-libgcc, $(LDFLAGS))
+else
 # Strip -Werror during linking for the LTO bootstrap
 GCC_LINKERFLAGS = $(filter-out -Werror, $(ALL_LINKERFLAGS))
+GCC_LDFLAGS = $(LDFLAGS)
+endif
 
-GCC_LINK=$(LINKER) $(GCC_LINKERFLAGS) $(LDFLAGS)
-GCC_LLINK=$(LLINKER) $(GCC_LINKERFLAGS) $(LDFLAGS)
+GCC_LINK=$(LINKER) $(GCC_LINKERFLAGS) $(GCC_LDFLAGS)
+GCC_LLINK=$(LLINKER) $(GCC_LINKERFLAGS) $(GCC_LDFLAGS)
 
 # Lists of files for various purposes.
 
-- 
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