[cfe-dev] libclang crash when parsing MS-style inline assembly

Thu Nov 7 20:16:17 PST 2013

On 07/11/2013 18:10, Richard Barton wrote:
> Hi all
>
> [Adding Alp - didn't realise he was missed off my original mail.]
>
> Looking at the code in lib/Parse/ParseStmt.cpp it looks as though this test
> can only be expected to pass when targeting x86 or x86_64. Any other
> architecture emits the "Unsupported architecture 'aarch64' for MS-style
> inline assembly" message.
>
> I'd like to XFAIL the test for all the other backends. I've committed the
> patch (r194211) Please holler if you disagree.

Hello Richard, thanks for CCing me in and for the XFAIL quick fix.

Your suggestion to combine the two messages could be a good idea.

Alternatively maybe we could move the err_msasm_unable_to_create_target
check before err_msasm_unsupported_arch, or maybe even remove
err_msasm_unsupported_arch completely and get the target ASM parser to
diagnose the condition?

I haven't been able to try these out because c-index-test doesn't accept
a target triple as far as I can tell, so it's been difficult to work with.

Open to suggestions here, and I've already got it on my long-term TODO
list to revisit this.

Also the original reporter should file a bug regarding how to enable the
feature in libclang or it will be forgotten. I think that one is a
legitimate feature request.

Alp.

>
> Thanks,
> Rich
>
>
>> -----Original Message-----
>> From: cfe-dev-bounces at cs.uiuc.edu [mailto:cfe-dev-bounces at cs.uiuc.edu] On
>> Behalf Of Richard Barton
>> Sent: 04 November 2013 15:25
>> To: mcrosier at codeaurora.org; William Ledoux
>> Cc: cfe-dev at cs.uiuc.edu
>> Subject: Re: [cfe-dev] libclang crash when parsing MS-style inline
> assembly
>> Hi all
>>
>> Apologies in advance that I don't fully understand the technicalities of
> this area,
>> but could that regression test be made more robust?
>>
>> My clang build has LLVM_DEFAULT_TARGET=aarch64-none-eabi (Host is
>> x86_64-linux-gnueabi) and the error message that I get is slightly
> different
>> causing the test to fail:
>>
>> .../ms-asm-no-target.cpp:8:3: error: Unsupported architecture 'aarch64'
> for MS-
>> style inline assembly
>>
>> Again, I don't fully understand the area, but the test seems only to
> require that
>> an x86 backend is available. It doesn't account for cross-compiling or
> when the
>> default triple is not x86. If the test needs to be run on x86, shouldn't
> the
>> REQUIRES line be more strict? Alternatively, if my failure mode is equally
>> acceptable behaviour, could the two error messages be combined?
>>
>> Thanks,
>> Rich
>>
>>
>>> -----Original Message-----
>>> From: cfe-dev-bounces at cs.uiuc.edu [mailto:cfe-dev-bounces at cs.uiuc.edu]
>>> On Behalf Of mcrosier at codeaurora.org
>>> Sent: 30 October 2013 15:58
>>> To: William Ledoux
>>> Cc: cfe-dev at cs.uiuc.edu
>>> Subject: Re: [cfe-dev] libclang crash when parsing MS-style inline
>> assembly
>>>> Hi Chad,
>>>>
>>>> So now I understand that there is no way to parse MS-style inline
>>>> assembly without a target asm parser.
>>>> But I still need to figure out if I can and how to tell libclang to
>>>> initialize a specific target.
>>> Unfortunately, I don't have an answer here.  Perhaps Alp or another
>>> member
>> of
>>> the list has a solution.
>>>
>>>> On Wed, Oct 30, 2013 at 4:27 PM, <mcrosier at codeaurora.org> wrote:
>>>>
>>>>> Hi William,
>>>>> I can answer your second question.  GCC style inline assembly does
>>>>> not require a target AsmParser.  MS-style inline assembly requires
>>>>> a parser because this is how we discover the constraints.  Hope
>>>>> this
>> helps.
>>>>>  Chad
>>>>>
>>>>>> Hi Alp,
>>>>>>
>>>>>> Thanks for helping !
>>>>>>
>>>>>> 1] Is there a way I could tell libclang which target to
>>>>>> initialize
>>>>> without
>>>>>> modifying it ?
>>>>>> 2] How does it work for gcc style assembly, is there a similar
>>>>>> error message or does it work without the need of any targets ?
>>>>>> 3] Since you decided to diagnose this, you might also want to
>>>>>> check
>>>>> the
>>>>>> case were the target have been initialized, but not the used
>>>>>> function pointers of this target
>>>>>>
>>>>>> William.
>>>>>>
>>>>>>
>>>>>> On Wed, Oct 30, 2013 at 3:53 PM, Alp Toker <alp at nuanti.com> wrote:
>>>>>>
>>>>>>>  Hello William,
>>>>>>>
>>>>>>> I've landed a fix in r193685 to diagnose this instead of crashing:
>>>>>>>
>>>>>>> clang/test/Index/ms-asm-no-target.cpp:8:3: error: MS-style
>>>>>>> inline assembly is not available: Unable to find target for this
>>>>>>> triple (no targets
>>>>> are
>>>>>>> registered)
>>>>>>>
>>>>>>> It's up to the embedder to decide what targets are linked in, so
>>>>>>> how
>>>>> the
>>>>>>> API exposes that is still an open question.
>>>>>>>
>>>>>>> Alp.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 30/10/2013 11:50, William Ledoux wrote:
>>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> The following minimal code that contain MS-style inline assembly
>>>>>>> will compile fine with clang, but libclang fails to parse it
>>>>>>> (clang_parseTranslationUnit will return NULL).
>>>>>>>
>>>>>>>    void Break(){ __asm { int 3 } }
>>>>>>>
>>>>>>> In yesterday's llvm and clang sources, the problem occurs in
>>>>>>> ParseMicrosoftAsmStatement.
>>>>>>> In the code below, because no target have been registered, the
>>>>>>> first line will set TheTarget to NULL, and the second line will
>>>>>>> dereference TheTarget, thus causing the problem.
>>>>>>>
>>>>>>>    const llvm::Target *TheTarget =
>>>>>>> llvm::TargetRegistry::lookupTarget(TT,
>>>>>>> Error);
>>>>>>>    OwningPtr<llvm::MCRegisterInfo>
>>>>> MRI(TheTarget->createMCRegInfo(TT));
>>>>>>> For what I understood, clang, in cc1_main, will initialize
>>>>>>> targets
>>>>> and
>>>>>>> targets' functions with the following 4 lines, whereas libclang
>>>>> won't.
>>>>>>>   llvm::InitializeAllTargets();
>>>>>>>   llvm::InitializeAllTargetMCs();
>>>>>>>   llvm::InitializeAllAsmPrinters();
>>>>>>>   llvm::InitializeAllAsmParsers();
>>>>>>>
>>>>>>> Just for testing purpose, adding those 4 lines somewhere in
>>>>>>> clang_createIndex fixes the problem. I know this is probably
>>>>>>> wrong,
>>>>> but
>>>>>>> did
>>>>>>> it just to see if more problems were hiding behind.
>>>>>>>
>>>>>>> So my questions are:
>>>>>>>   1] Is it wanted that libclang doesn't initialize any target ?
>>>>>>>   2] if yes, how shloud it behave with MS inline assembly ?
>>>>>>>   3] if no, what is the proper way to make it initialize targets ?
>>>>>>>
>>>>>>> Many thanks for you work !
>>>>>>> William
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> View this message in context:
>>>>>>>
>>>>> http://clang-developers.42468.n3.nabble.com/libclang-crash-when-par
>>>>> si ng-MS-style-inline-assembly-tp4035432.html
>>>>>>> Sent from the Clang Developers mailing list archive at Nabble.com.
>>>>>>> _______________________________________________
>>>>>>> cfe-dev mailing
>>>>>>> listcfe-dev at cs.uiuc.eduhttp://
>>>>> lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>>>>
>>>>>>> -- http://www.nuanti.com
>>>>>>> the browser experts
>>>>>>>
>>>>>>>
>>>>>> _______________________________________________
>>>>>> cfe-dev mailing list
>>>>>> cfe-dev at cs.uiuc.edu
>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>>>
>>>>>
>>>>>
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>

-- 
http://www.nuanti.com
the browser experts