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On 22/09/16 20:22 +0200, Christophe Lyon wrote:
On 22 September 2016 at 15:25, Jonathan Wakely <jwakely@redhat.com> wrote:On 22/09/16 12:15 +0100, Jonathan Wakely wrote:On 22/09/16 11:16 +0100, Jonathan Wakely wrote:(Somebody should fix PR58938 so exception_ptr is portable).Christophe, would you be able to test this patch? It uses a single global mutex for exception_ptr objects, which doesn't scale well but that probably isn't a problem for processors without lock-free atomics for single words. This also solves the problem of mismatched -march options, where the header is compiled for a CPU that supports the atomics but libstdc++.so was built for an older CPU that doesn't support them, and linking fails (as in https://gcc.gnu.org/PR58938#c13).We'd also need something like this extra piece, to ensure we don't leak exceptions. Currently __gxx_exception_cleanup assumes that if ATOMIC_INT_LOCK_FREE < 2 the referenceCount can never be greater than 1, because there are not exception_ptr objects that could increase it. If we enable exception_ptr unconditionally then that assumption doesn't hold. This patch uses the exception_ptr code to do the cleanup, under the same mutex as any other increments and decrements of the reference count. It's a bit of a hack though.Should I have applied this one on top of the other? I ran a validation with it alone, and arm-none-eabi with default mode, cpu, and fpu does not build:
That's expected, the second patch requires the first one (you can't use exception_ptr unconditionally if it's only defined conditionally :-)
In file included from /tmp/9260164_29.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/libsupc++/eh_throw.cc:27:0: /tmp/9260164_29.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/libsupc++/exception_ptr.h:43:4: error: #error This platform does not support exception propagation. # error This platform does not support exception propagation. ^~~~~ make[4]: *** [eh_throw.lo] Error 1 In addition, on arm-none-eabi --with-mode=thumb --with-cpu=cortex-a9, I've noticed a regression in c++ - PASS now FAIL [PASS => FAIL]: g++.dg/opt/pr36449.C -std=gnu++11 execution test g++.dg/opt/pr36449.C -std=gnu++14 execution test g++.dg/opt/pr36449.C -std=gnu++98 execution test My logs show: qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Strange, I don't see how my patch could cause that.
The validation of the other patch is still running: I had to re-run it because the patch didn't apply because of the ChangeLog entry.
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