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

[Richard Barton]

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-parsi
> >> 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
> >> >>
> >> >>
> >> > _______________________________________________
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> >> >
> >>
> >>
> >>
> >
> 
> 
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