[cfe-dev] SIGILL with clang

[ROHIT KUMAR via cfe-dev]

Thanks guys, the issue is resolved now. It was a more trivial fix. Gcc was
not giving any error neither on compile time nor on run time. Clang was
giving error on runtime.
It was an issue with a function which was supposed to return a Boolean but
it wasn't. I could not figure it out earlier because debugging was not
working. But when I got it working I could pinpoint the function, someone
from llvm-dev thread suggested to check for such a function. So, finally it
got fixed.

On Aug 29, 2017 12:13 AM, "John McCall via cfe-dev" <cfe-dev at lists.llvm.org>
wrote:

>
> > On Aug 27, 2017, at 7:11 PM, Csaba Raduly via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
> >
> > Hi,
> > foo() has undefined behavior if i==0 (lack of return statement)
> >
> > 6.6.3 para 2:
> > Flowing off the end of a function is equivalent to a return with no
> > value; this results in undefined behavior
> > in a value-returning function.
> >
> > clang generates an invalid instruction for undefined behavior.
> > This is not ARM-specific.
>
> Note that this is C++-specific; it is only undefined behavior in C if the
> result is used by the caller.
>
> John.
>
> >
> > https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(j:1,
> source:'int+foo(int+i)+%7B%0A+if(i)+%7B%0A+++return+1%3B%0A+
> %7D%0A%7D%0A%0Aint+main()+%7B%0A+foo(0)%3B%0A%7D%0A'),l:'5',
> n:'0',o:'C%2B%2B+source+%231',t:'0')),k:50,l:'4',n:'0',o:'',
> s:0,t:'0'),(g:!((h:compiler,i:(compiler:clang400,filters:(__
> _0:(),b:'0',commentOnly:'0',directives:'0',intel:'0',
> jquery:'3.2.1',length:1,prevObject:(___0:(),length:1,prevObject:(___0:(
> jQuery3210202339019067484751:(display:'')),length:1)),trim:'
> 0'),options:'-O0',source:1),l:'5',n:'0',o:'x86-64+clang+4.0.
> 0+(Editor+%231,+Compiler+%231)',t:'0')),k:50,l:'4',n:'0',o:'
> ',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4
> >
> > That ud2 instruction is the machine code for undefined behavior.
> >
> > Csaba
> >
> >
> > On Sat, Aug 26, 2017 at 12:32 PM, Raphael Isemann via cfe-dev
> > <cfe-dev at lists.llvm.org> wrote:
> >> Glad to help. CCing ML for the record.
> >>
> >> On Aug 26, 2017 12:24 PM, "ROHIT KUMAR" <rohitpoddar92 at gmail.com>
> wrote:
> >>
> >> It is as you mentioned. The missing return statement in a function very
> much
> >> similar to your example. Adding it fixed the issue
> >>
> >> So, it seems Clang is a little too strict as compared to GCC. I faced
> many
> >> issues earlier and all of them ended up being related to flags, I didn't
> >> expect the issue to be this simple.
> >>
> >> Thanks for your help
> >>
> >>
> >>
> >>
> >>
> >> On Sat, Aug 26, 2017 at 3:14 PM, Raphael Isemann <teemperor at gmail.com>
> >> wrote:
> >>>
> >>> On a side note that is probably too simple for the ML: Did you check
> >>> for missing return statements in the called/callee function? For a
> >>> missing return clang generates SIGILL while GCC is returning something
> >>> ABI-dependent IIRC.
> >>>
> >>> E.g. this causes SIGILL on clang and runs just fine on GCC:
> >>> ```
> >>> int foo(int i) {
> >>> if(i) {
> >>>   return 1;
> >>> }
> >>> }
> >>>
> >>> int main() {
> >>> foo(0);
> >>> }
> >>> ```
> >>>
> >>> - Raphael
> >>>
> >>>
> >>> 2017-08-26 10:34 GMT+02:00 ROHIT KUMAR via cfe-dev
> >>> <cfe-dev at lists.llvm.org>:
> >>>> Hey folks,
> >>>>
> >>>> I am migrating our huge Android code base from GCC(Eclipse IDE) to
> >>>> clang(Android Studio).
> >>>>
> >>>> Error: SIGILL (signal SIGILL: illegal instruction)
> >>>>
> >>>> At a weird line in the code, I am getting this error. which points to
> a
> >>>> closing curly bracket of an if condition. After googling, I am
> assuming
> >>>> it
> >>>> is some kind of architecture flag issue. I am using same flags which
> >>>> were
> >>>> used for GCC.
> >>>>
> >>>> Note: I am currently working on Arm build.
> >>>>
> >>>> Here are the architecture flags for ARM7:
> >>>>
> >>>> -march=armv7-a -mfloat-abi=softfp -mfpu=vfpv3-d16 -mtune=cortex-a8
> >>>> -mthumb
> >>>> -DTARGET_THUMB2
> >>>>
> >>>> Can anyone help me debug this issue? Is there any issue with the flags
> >>>> with
> >>>> clang?
> >>>>
> >>>> Thanks,
> >>>> Rohit Kumar
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> cfe-dev mailing list
> >>>> cfe-dev at lists.llvm.org
> >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >>>>
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >>
> >
> >
> >
> > --
> > GCS a+ e++ d- C++ ULS$ L+$ !E- W++ P+++$ w++$ tv+ b++ DI D++ 5++
> > The Tao of math: The numbers you can count are not the real numbers.
> > Life is complex, with real and imaginary parts.
> > "Ok, it boots. Which means it must be bug-free and perfect. " -- Linus
> Torvalds
> > "People disagree with me. I just ignore them." -- Linus Torvalds
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