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Re: [PATCH] PR target/80556


On 28 Jun 2017, at 18:40, Jeff Law <law@redhat.com> wrote:
> 
> On 06/09/2017 07:57 AM, Simon Wright wrote:
>>        2017-06-09 Simon Wright <simon@pushface.org>
>> 
>>        PR target/80556
>>        * configure.ac (stage1_ldflags): For Darwin, include -lSystem.
>>          (poststage1_ldflags): likewise.
>>        * configure: regenerated.
> I'm a bit confused here.  Isn't -lSystem included in darwin's LIB_SPEC
> in which case the right things ought to already be happening, shouldn't it?

The specs that involve -lSystem are

*link_gcc_c_sequence:
%:version-compare(>= 10.6 mmacosx-version-min= -no_compact_unwind)    %{!static:%{!static-libgcc:       %:version-compare(>= 10.6 mmacosx-version-min= -lSystem) } }    %{fno-pic|fno-PIC|fno-pie|fno-PIE|fapple-kext|mkernel|static|mdynamic-no-pic:       %:version-compare(>= 10.7 mmacosx-version-min= -no_pie) } %G %L

*lib:
%{!static:-lSystem}

but I also see

*libgcc:
%{static-libgcc|static: -lgcc_eh -lgcc; ....

which might be the root of the problem?

Looking at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80556#c39, I report that

   $ gnatmake raiser -largs -static-libgcc -static-libstdc++

resulted in the link command

   /usr/bin/ld -dynamic -arch x86_64 -macosx_version_min 10.12.0
   -weak_reference_mismatches non-weak -o raiser -L./
   -L/opt/gcc-7.1.0/lib/gcc/x86_64-apple-darwin15/7.1.0/adalib/
   -L/opt/gcc-7.1.0/lib/gcc/x86_64-apple-darwin15/7.1.0
   -L/opt/gcc-7.1.0/lib/gcc/x86_64-apple-darwin15/7.1.0/../../.. b~raiser.o
   ./raiser.o -v
   /opt/gcc-7.1.0/lib/gcc/x86_64-apple-darwin15/7.1.0/adalib/libgnat.a
   -no_compact_unwind -lgcc_eh -lgcc -lSystem

i.e. -lSystem is *after* -lgcc, so that its exception handling won't be invoked.

I don't know what -lgcc_eh does, but my patch would be pretty much equivalent to changing the libgcc spec above to

*libgcc:
%{static-libgcc|static: -lSystem -lgcc_eh -lgcc; ....

and if that would be OK it would obviously be much better.

I've rebuilt gcc-8-20170528 with this change alone (i.e. not the patch currently posted here), successfully.

If I propose this alternative patch, should it be a new post, or should I continue this thread?

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