On 15 November 2016 at 12:50, Jonathan Wakely <jwak...@redhat.com> wrote:
> On 14/11/16 14:32 +0100, Christophe Lyon wrote:
>>
>> On 20 October 2016 at 19:40, Jonathan Wakely <jwak...@redhat.com> wrote:
>>>
>>> On 20/10/16 10:33 -0700, Mike Stump wrote:
>>>>
>>>>
>>>> On Oct 20, 2016, at 9:34 AM, Jonathan Wakely <jwak...@redhat.com> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On 20/10/16 09:26 -0700, Mike Stump wrote:
>>>>>>
>>>>>>
>>>>>> On Oct 20, 2016, at 5:20 AM, Jonathan Wakely <jwak...@redhat.com>
>>>>>> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I am considering leaving this in the ARM backend to force people to
>>>>>>> think what they want to do about thread safety with statics and C++
>>>>>>> on bare-metal systems.
>>>>>
>>>>>
>>>>>
>>>>> The quoting makes it look like those are my words, but I was quoting
>>>>> Ramana from https://gcc.gnu.org/ml/gcc-patches/2015-05/msg02751.html
>>>>>
>>>>>> Not quite in the GNU spirit? The port people should decide the best
>>>>>> way
>>>>>> to get as much functionality as possible and everything should just
>>>>>> work, no
>>>>>> sharp edges.
>>>>>>
>>>>>> Forcing people to think sounds like a sharp edge?
>>>>>
>>>>>
>>>>>
>>>>> I'm inclined to agree, but we are talking about bare metal systems,
>>>>
>>>>
>>>>
>>>> So? gcc has been doing bare metal systems for more than 2 years now.
>>>> It
>>>> is pretty good at it. All my primary targets today are themselves bare
>>>> metal systems (I test with newlib).
>>>>
>>>>> where there is no one-size-fits-all solution.
>>>>
>>>>
>>>>
>>>> Configurations are like ice cream cones. Everyone gets their flavor no
>>>> matter how weird or strange. Putting nails in a cone because you don't
>>>> know
>>>> if they like vanilla or chocolate isn't reasonable. If you want, make
>>>> two
>>>> flavors, and vend two, if you want to just do one, pick the flavor and
>>>> vend
>>>> it. Put an enum #define default_flavor vanilla, and you then have
>>>> support
>>>> for any flavor you want. Want to add a configure option for the flavor
>>>> select, add it. You want to make a -mflavor=chocolate option, add it.
>>>> gcc
>>>> is literally littered with these things.
>>>
>>>
>>>
>>> Like I said, you can either build the library with
>>> -fno-threadsafe-statics or you can provide a definition of the missing
>>> symbol.
>>>
>> I gave this a try (using CXXFLAGS_FOR_TARGET=-fno-threadsafe-statics).
>> It seems to do the trick indeed: almost all tests now pass, the flag is
>> added
>> to testcase compilation.
>>
>> Among the 6 remaining failures, I noticed these two:
>> - experimental/type_erased_allocator/2.cc: still complains about the
>> missing
>> __sync_synchronize. Does it need dg-require-thread-fence?
>
>
> Yes, I think that test actually uses atomics directly, so does depend
> on the fence.
>
I've attached the patch to achieve this.
Is it OK?
>> - abi/header_cxxabi.c complains because the option is not valid for C.
>> I can see the test is already skipped for other C++-only options: it is OK
>> if I submit a patch to skip it if -fno-threadsafe-statics is used?
>
>
> Yes, it makes sense there too.
This one is not as obvious as I hoped. I tried:
-// { dg-skip-if "invalid options for C" { *-*-* } { "-std=c++??"
"-std=gnu++??" } }
+// { dg-skip-if "invalid options for C" { *-*-* } { "-std=c++??"
"-std=gnu++??" "-fno-threadsafe-statics" } }
but it does not work.
I set CXXFLAGS_FOR_TARGET=-fno-threadsafe-statics
before running GCC's configure.
This results in -fno-threadsafe-statics being used when compiling the tests,
but dg-skip-if does not consider it: it would if I passed it via
runtestflags/target-board, but then it would mean passing this flag
to all tests, not only the c++ ones, leading to errors everywhere.
Am I missing something?
Thanks,
Christophe
>> I think I'm going to use this flag in validations from now on (target
>> arm-none-eabi
>> only, with default mode/cpu/fpu).
>
>
> Thanks for the update on this.
>
libstdc++-v3/ChangeLog:
2016-11-16 Christophe Lyon <christophe.l...@linaro.org>
* testsuite/experimental/type_erased_allocator/2.cc: Add
dg-require-thread-fence.
diff --git a/libstdc++-v3/testsuite/experimental/type_erased_allocator/2.cc
b/libstdc++-v3/testsuite/experimental/type_erased_allocator/2.cc
index 216a88c..0b73359 100644
--- a/libstdc++-v3/testsuite/experimental/type_erased_allocator/2.cc
+++ b/libstdc++-v3/testsuite/experimental/type_erased_allocator/2.cc
@@ -1,4 +1,5 @@
// { dg-do run { target c++14 } }
+// { dg-require-thread-fence "" }
// Copyright (C) 2015-2016 Free Software Foundation, Inc.
//
