Re: [PATCH 2/2] PR libstdc++/86756 Move rest of std::filesystem to libstdc++.so

[Jonathan Wakely <jwakely@redhat.com>]

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On 23/01/19 17:01 +0100, Christophe Lyon wrote:
>On Wed, 23 Jan 2019 at 16:28, Jonathan Wakely <jwakely@redhat.com> wrote:
>>
>> On 09/01/19 13:53 +0100, Christophe Lyon wrote:
>> >On Wed, 9 Jan 2019 at 11:11, Jonathan Wakely <jwakely@redhat.com> wrote:
>> >>
>> >> On 09/01/19 10:09 +0000, Jonathan Wakely wrote:
>> >> >On 08/01/19 11:13 +0100, Christophe Lyon wrote:
>> >> >>On aarch64, I'm seeing an addtional:
>> >> >>FAIL: 27_io/filesystem/path/compare/strings.cc execution test
>> >> >>because:
>> >> >>/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc:39:
>> >> >>void test01(): Assertion 'p.compare(p0) == p.compare(s0)' failed.
>> >> >
>> >> >Odd, I don't know why that would be target-specific. It's probably
>> >> >just latent on other targets. I'll try to reproduce it on my aarch64
>> >> >system, but it will take a while to build current trunk.
>> >> >
>> >> >If you have time, could you please apply this patch, re-run that test
>> >>
>> >> *This* patch:
>> >>
>> >> --- a/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc
>> >> +++ b/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc
>> >> @@ -36,6 +36,7 @@ test01()
>> >>      path p(s);
>> >>      VERIFY( p.compare(s) == 0 );
>> >>      VERIFY( p.compare(s.c_str()) == 0 );
>> >> +    __builtin_printf("Comparing %s as path:%d as string:%d\n", s.c_str(), p.compare(p0), p.compare(s0));
>> >>      VERIFY( p.compare(p0) == p.compare(s0) );
>> >>      VERIFY( p.compare(p0) == p.compare(s0.c_str()) );
>> >>    }
>> >>
>> >>
>> >>
>> >>
>> >> >(cd $target/libstdc++-v3 && make check
>> >> >RUNTESTFLAGS=conformance.exp=*/path/compare/strings/cc) and send me
>> >> >the output from the $target/libstdc++-v3/testsuite/libstdc++.log file?
>> >> >
>> >> >On x86_64 I get:
>> >> >
>> >> >Comparing  as path:-1 as string:-1
>> >> >Comparing / as path:-1 as string:-1
>> >> >Comparing // as path:-1 as string:-1
>> >> >Comparing /. as path:-51 as string:-51
>> >> >Comparing /./ as path:-51 as string:-51
>> >> >Comparing /a as path:-2 as string:-2
>> >> >Comparing /a/ as path:-1 as string:-1
>> >> >Comparing /a// as path:-1 as string:-1
>> >> >Comparing /a/b/c/d as path:1 as string:1
>> >> >Comparing /a//b as path:1 as string:1
>> >> >Comparing a as path:-1 as string:-1
>> >> >Comparing a/b as path:-1 as string:-1
>> >> >Comparing a/b/ as path:-1 as string:-1
>> >> >Comparing a/b/c as path:-1 as string:-1
>> >> >Comparing a/b/c.d as path:-1 as string:-1
>> >> >Comparing a/b/.. as path:-1 as string:-1
>> >> >Comparing a/b/c. as path:-1 as string:-1
>> >> >Comparing a/b/.c as path:-1 as string:-1
>> >> >PASS: 27_io/filesystem/path/compare/strings.cc execution test
>> >> >
>> >
>> >Here is what I have on aarch64-none-elf:
>> >Comparing  as path:-1 as string:-1^M
>> >Comparing / as path:-1 as string:-1^M
>> >Comparing // as path:-1 as string:-1^M
>> >Comparing /. as path:-102 as string:-51^M
>> >/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc:40:
>> >void test01(): Assertion 'p.compare(p0) == p.compare(s0)' failed.^M
>> >^M
>> >*** EXIT code 4242^M
>> >emu: host signal 6^M
>> >FAIL: 27_io/filesystem/path/compare/strings.cc execution test
>>
>> This is a strange one. With my aarch64-unknown-linux-gnu trunk build I get:
>>
>> Comparing /. as path:-51 as string:-51
>>
>> Which suggests it's a newlib vs glibc difference, but this target uses
>> glibc (right?) and has the same FAIL:
>> https://gcc.gnu.org/ml/gcc-testresults/2019-01/msg02276.html
>
>Yes, it uses glibc-2.28
>
>That build has this in its libstdc++.log:
>/home/tcwg-buildslave/workspace/tcwg-buildfarm_0/snapshots/gcc.git~master_rev_2e9ceebcd7618d0e068e0029b43cd75d679022d7/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc:39:
>void test01(): Assertion 'p.compare(p0) == p.compare(s0)' failed.
>timeout: the monitored command dumped core
>FAIL: 27_io/filesystem/path/compare/strings.cc execution test
>
>
>>
>> The test should be reducable to simply:
>>
>> // { dg-options "-std=gnu++17" }
>> #include <string>
>> #include <string_view>
>>
>> int main()
>> {
>>   std::string_view s0 = "a";
>>   std::string p0(s0);
>>   std::string p(".");
>>   __builtin_printf("as path:%d as string:%d\n", p.compare(p0), p.compare(s0));
>> }
>>
>> Again, I get -51 and -51 for this. Could you test it on
>> aarch64-none-elf?
>>
>> In terms of what the standard requires, this comparison is based on
>> strcmp, i.e. it only specifies a result less than zero, equal to zero,
>> or greater than zero. But I'd like to know why the comparisons aren't
>> returning the same consistent value.
>>
>
>I get:
>as path:-102 as string:-102

I have no idea what's going on here, so I think I will just change the
test to only care about the sign of the result, as in the attached
patch.



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commit 84fc5b9d432788414e75df1f62bf8645db57f395
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jan 24 12:53:45 2019 +0000

    Fix failing test due to inconsistent strcmp results
    
            * testsuite/27_io/filesystem/path/compare/strings.cc: Only compare
            sign of results.

diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc
index 3f0aa4bde06..83487ae35b6 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/compare/strings.cc
@@ -26,6 +26,8 @@
 
 using std::filesystem::path;
 
+int sign(int i) { return i > 0 ? 1 : i < 0 ? -1 : 0; }
+
 void
 test01()
 {
@@ -36,8 +38,8 @@ test01()
     path p(s);
     VERIFY( p.compare(s) == 0 );
     VERIFY( p.compare(s.c_str()) == 0 );
-    VERIFY( p.compare(p0) == p.compare(s0) );
-    VERIFY( p.compare(p0) == p.compare(s0.c_str()) );
+    VERIFY( sign(p.compare(p0)) == sign(p.compare(s0)) );
+    VERIFY( sign(p.compare(p0)) == sign(p.compare(s0.c_str())) );
   }
 }