r207696 - PR19601: std::remove_if does not really remove the elements.

[Richard Smith]

On Thu, May 1, 2014 at 7:47 AM, Arnaud Allard de Grandmaison <
arnaud.adegm at gmail.com> wrote:

> I modified the test so that it now catches all cases:
>
>    - no remove_if (and thus no erase) : fail
>    - remove_if : fail
>    - remove_if + erase : pass
>
> The test is however not robust in face of appending more options in the
> stripPositionalArgs : for now it has the minimal number of
> '-no-integrated-as' to catch the issues we have had, and we could add some
> more to have a reasonnable margin. Thoughts ?
>

This is fine; there's not much chance of someone accidentally introducing
the same bug for the same argument again. (We're really just guarding
against your change being lost by a merge conflict or similar, and this
test does that.)


> Cheers,
> --
> Arnaud
>
>
> On Thu, May 1, 2014 at 2:57 AM, Richard Smith <richard at metafoo.co.uk>wrote:
>
>> On Wed, Apr 30, 2014 at 4:31 PM, Arnaud Allard de Grandmaison <
>> arnaud.adegm at gmail.com> wrote:
>>
>>> Dumping Args before & after the remove_if shows that Jordan is right:
>>>  - before: Args: clang-tool -target x86_64 -no-integrated-as -c -v -c
>>> placeholder.cpp
>>>  - after: Args: clang-tool -target x86_64 -c -v -c placeholder.cpp
>>> placeholder.cpp
>>> and later on, _all_ input files are dropped. So we were just lucky.
>>>
>>> The code in stripPositionalArgs appends some arguments (-c
>>> placeholder.cpp), so I can not force -no-integrated-as to be last from the
>>> command line.
>>>
>>>  This would require to adapt stripPositionalArgs so that it prepends its
>>> arguments and we can test for the missing erase. Do we still want a
>>> testcase for that ? It seems a bit like an overshoot to me, but I aggree
>>> that there as been several incorrect commits in the same place.
>>>
>>
>> Easier test: add -no-integrated-as *repeatedly*. If you add it enough
>> times, it'll be in the tail of unchanged elements left behind by remove_if.
>>
>>
>>> On Thu, May 1, 2014 at 12:46 AM, Richard Smith <richard at metafoo.co.uk>wrote:
>>>
>>>> On Wed, Apr 30, 2014 at 3:40 PM, Arnaud Allard de Grandmaison <
>>>> arnaud.adegm at gmail.com> wrote:
>>>>
>>>>> I have not been able to come up with a testcase which does better than
>>>>> what test/Tooling/multi-jobs.cpp already does.
>>>>>
>>>>> The current test status:
>>>>>  1. no remove_if (and thus no erase) : multi-jobs fails
>>>>>  2. remove_if : multi-jobs pass
>>>>>  3. remove_if + erase : multi-jobs pass
>>>>>
>>>>> Invoking clang-check with '-v' shows that in cases 2 & 3 the
>>>>> -no-integrated-as has been dropped. I feel a bit like hunting a red herring
>>>>> there : depending on the argument position, it gets dropped or not.
>>>>> Jordan's hypothesis is probably right.
>>>>>
>>>>
>>>> Try putting it at the end of the command line.
>>>>
>>>>
>>>>>  Cheers,
>>>>> --
>>>>> Arnaud
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Apr 30, 2014 at 11:30 PM, Jordan Rose <jordan_rose at apple.com>wrote:
>>>>>
>>>>>> My hypothesis for how this was working: std::remove_if reorders
>>>>>> elements using std::move, so we were getting lucky that -no-integrated-as
>>>>>> wasn't the last argument and something else got moved on top of it. We'd
>>>>>> have duplicates of the last few arguments (because they got moved earlier),
>>>>>> but that wouldn't show -no-integrated-as.
>>>>>>
>>>>>> Jordan
>>>>>>
>>>>>>
>>>>>> On Apr 30, 2014, at 14:09, Richard Smith <richard at metafoo.co.uk>
>>>>>> wrote:
>>>>>>
>>>>>> This needs a test case. This code has already been committed,
>>>>>> incorrectly, twice before this revision; the existing test case clearly
>>>>>> doesn't actually cover it properly.
>>>>>>
>>>>>>
>>>>>> On Wed, Apr 30, 2014 at 12:59 PM, Arnaud A. de Grandmaison <
>>>>>> arnaud.adegm at gmail.com> wrote:
>>>>>>
>>>>>>> Author: aadg
>>>>>>> Date: Wed Apr 30 14:59:22 2014
>>>>>>> New Revision: 207696
>>>>>>>
>>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=207696&view=rev
>>>>>>> Log:
>>>>>>> PR19601: std::remove_if does not really remove the elements.
>>>>>>>
>>>>>>> It moves them at the end of the range instead, so an extra erase is
>>>>>>> needed.
>>>>>>>
>>>>>>> It is strange that this code works without the erase. On the other
>>>>>>> hand, removing the remove_if will make fail some tests.
>>>>>>>
>>>>>>> Modified:
>>>>>>>     cfe/trunk/lib/Tooling/CompilationDatabase.cpp
>>>>>>>
>>>>>>> Modified: cfe/trunk/lib/Tooling/CompilationDatabase.cpp
>>>>>>> URL:
>>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Tooling/CompilationDatabase.cpp?rev=207696&r1=207695&r2=207696&view=diff
>>>>>>>
>>>>>>> ==============================================================================
>>>>>>> --- cfe/trunk/lib/Tooling/CompilationDatabase.cpp (original)
>>>>>>> +++ cfe/trunk/lib/Tooling/CompilationDatabase.cpp Wed Apr 30
>>>>>>> 14:59:22 2014
>>>>>>> @@ -238,8 +238,9 @@ static bool stripPositionalArgs(std::vec
>>>>>>>
>>>>>>>    // Remove -no-integrated-as; it's not used for syntax checking,
>>>>>>>    // and it confuses targets which don't support this option.
>>>>>>> -  std::remove_if(Args.begin(), Args.end(),
>>>>>>> -                 MatchesAny(std::string("-no-integrated-as")));
>>>>>>> +  Args.erase(std::remove_if(Args.begin(), Args.end(),
>>>>>>> +
>>>>>>>  MatchesAny(std::string("-no-integrated-as"))),
>>>>>>> +             Args.end());
>>>>>>>
>>>>>>>    const std::unique_ptr<driver::Compilation> Compilation(
>>>>>>>        NewDriver->BuildCompilation(Args));
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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