[Lldb-commits] [lldb] r316673 - Allow SysV-i386 ABI on everything other than Apple targets

[Jason Molenda via lldb-commits]

> On Oct 26, 2017, at 3:12 PM, Davide Italiano <dccitaliano at gmail.com> wrote:
> 
> On Thu, Oct 26, 2017 at 3:04 PM, Jason Molenda <jmolenda at apple.com> wrote:
>> 
>> 
>>> On Oct 26, 2017, at 10:24 AM, Davide Italiano via lldb-commits <lldb-commits at lists.llvm.org> wrote:
>>> 
>>> On Thu, Oct 26, 2017 at 10:04 AM, Stephane Sezer via lldb-commits
>>> <lldb-commits at lists.llvm.org> wrote:
>>>> Author: sas
>>>> Date: Thu Oct 26 10:04:20 2017
>>>> New Revision: 316673
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=316673&view=rev
>>>> Log:
>>>> Allow SysV-i386 ABI on everything other than Apple targets
>>>> 
>>>> Summary:
>>>> This matches other SysV ABIs that are different on Apple and non-Apple targets,
>>>> like `ABISysV_arm.cpp` for instance.
>>>> 
>>>> Reviewers: clayborg, emaste
>>>> 
>>>> Subscribers: aemerson, kristof.beyls, lldb-commits
>>>> 
>>>> Differential Revision: https://reviews.llvm.org/D39335
>>>> 
>>>> Modified:
>>>>   lldb/trunk/source/Plugins/ABI/SysV-i386/ABISysV_i386.cpp
>>>> 
>>>> Modified: lldb/trunk/source/Plugins/ABI/SysV-i386/ABISysV_i386.cpp
>>>> URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/ABI/SysV-i386/ABISysV_i386.cpp?rev=316673&r1=316672&r2=316673&view=diff
>>>> ==============================================================================
>>>> --- lldb/trunk/source/Plugins/ABI/SysV-i386/ABISysV_i386.cpp (original)
>>>> +++ lldb/trunk/source/Plugins/ABI/SysV-i386/ABISysV_i386.cpp Thu Oct 26 10:04:20 2017
>>>> @@ -205,11 +205,12 @@ ABISysV_i386::GetRegisterInfoArray(uint3
>>>> ABISP
>>>> ABISysV_i386::CreateInstance(lldb::ProcessSP process_sp, const ArchSpec &arch) {
>>>>  static ABISP g_abi_sp;
>>>> -  if ((arch.GetTriple().getArch() == llvm::Triple::x86) &&
>>>> -      (arch.GetTriple().isOSLinux() || arch.GetTriple().isOSFreeBSD())) {
>>>> -    if (!g_abi_sp)
>>>> -      g_abi_sp.reset(new ABISysV_i386(process_sp));
>>>> -    return g_abi_sp;
>>>> +  if (arch.GetTriple().getVendor() != llvm::Triple::Apple) {
>>>> +    if (arch.GetTriple().getArch() == llvm::Triple::x86) {
>>>> +      if (!g_abi_sp)
>>>> +        g_abi_sp.reset(new ABISysV_i386(process_sp));
>>>> +      return g_abi_sp;
>>>> +    }
>>>>  }
>>>>  return ABISP();
>>>> }
>>>> 
>>> 
>>> This seems to change a fairly fundamental function for lldb-i386.
>>> I think we should have an unit-test for this. Sorry for being
>>> pedantic, I promise I'll stop after this one.
>> 
>> 
>> It's a good suggestion, and not something we test today.  Right now there are two i386 ABIs that lldb supports:  Darwin and SysV.  This patch implements that correctly -- but the obvious problem is if a third i386 ABI is added in the future.  Now it's a race to see whether SysV-i386 or CrazyOtherABI-i386 gets CreateInstance'd, depending on the order they're registered or something.  And I'm not sure how you write a test today that would test a new target that uses CrazyOtherABI-i386 is getting the correct plugin activated.
>> 
>> 
> 
> Thanks for your reply, Jason. I'm not sure how to test this either,
> but I'll take a look.
> In theory, (or at lesat what I have in mind :)) you should be able to
> have a unit test that just allocates an object and calls
> createInstance() directly [if possible], then checks that the result
> is of the right type? [ABISysV_i386 vs ABIDarwin_i386 or something
> like that?]
> That won't of course take care of the race, but the test will break in
> case somebody deletes code from the function (and/or allocates an
> object with the wrong ABI).
> I think it's not testing this feature entirely (and I think testing
> the lack of races might be hard, but at least should give us some
> coverage [if nothing, to discriminate dead code VS non-dead code].
> To be fair, I haven't looked into how hard this is to get working, but
> I might. CC:ing Zachary, maybe he has some ideas.



Yep agree, this should be easy to do in a unit test.  I think it could be as simple as

ArchSpec arch("apple-i386-macosx");
ABISP m_abi_sp = ABI::FindPlugin(ProcessSP(), archspec);

if (m_abi_sp.get() == nullptr || m_abi_sp->GetPluginName() != ConstString("abi.macosx-i386"))
  fail;


I don't think any ABI actually needs a live Process object for their CreateInstance() methods today.  If it becomes necessary in the future, then that would need to be done for real in the unit test.


J