llvm dev - Nov 2012 - [LLVMdev] noreturn attribute on a call instruction vs noreturn on a function

Hi,

Building the following C code I get a call instruction that has no noreturn
attribute, while the function itself does have it.

void foo(void **b) {
  __builtin_longjmp(b, 1);
}


define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable {
entry:
  %0 = bitcast i8** %b to i8*
  tail call void @llvm.eh.sjlj.longjmp(i8* %0)
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
  unreachable
}

declare void @llvm.eh.sjlj.longjmp(i8*) noreturn nounwind 
<<<<<<<<<<<<<<<<<


I've hit this in asan where it checks the noreturn attribute in the call
instruction, but not in the function object.
Who is wrong here? Should asan also check noreturn in the called function?

Thanks,

--kcc
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Hi Kostya,

On 28/11/12 14:47, Kostya Serebryany wrote:
> Hi,
>
> Building the following C code I get a call instruction that has no noreturn
> attribute, while the function itself does have it.
>
> void foo(void **b) {
>    __builtin_longjmp(b, 1);
> }
>
>
> define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable {
> entry:
>    %0 = bitcast i8** %b to i8*
>    tail call void @llvm.eh.sjlj.longjmp(i8* %0)
>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>    unreachable
> }
>
> declare void @llvm.eh.sjlj.longjmp(i8*) noreturn nounwind 
<<<<<<<<<<<<<<<<<
>
>
> I've hit this in asan where it checks the noreturn attribute in the
call
> instruction, but not in the function object.
> Who is wrong here? Should asan also check noreturn in the called function?
I think you should consider the call no-return if either the call or the
callee has the no-return attribute.

Ciao, Duncan.
>
> Thanks,
>
> --kcc
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>

On Wed, Nov 28, 2012 at 8:05 PM, Duncan Sands <baldrick at free.fr> wrote:
> Hi Kostya,
>
>
> On 28/11/12 14:47, Kostya Serebryany wrote:
>
>> Hi,
>>
>> Building the following C code I get a call instruction that has no
>> noreturn
>> attribute, while the function itself does have it.
>>
>> void foo(void **b) {
>>    __builtin_longjmp(b, 1);
>> }
>>
>>
>> define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable {
>> entry:
>>    %0 = bitcast i8** %b to i8*
>>    tail call void @llvm.eh.sjlj.longjmp(i8* %0)
>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<**<<<<<<
>>    unreachable
>> }
>>
>> declare void @llvm.eh.sjlj.longjmp(i8*) noreturn nounwind
>>  <<<<<<<<<<<<<<<<<
>>
>>
>> I've hit this in asan where it checks the noreturn attribute in the
call
>> instruction, but not in the function object.
>> Who is wrong here? Should asan also check noreturn in the called
function?
>>
>
> I think you should consider the call no-return if either the call or the
> callee has the no-return attribute.
>
Thanks, I've fixed this in asan pass.

--kcc


>
> Ciao, Duncan.
>
>
>> Thanks,
>>
>> --kcc
>>
>>
>>
>> ______________________________**_________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>
http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>>
>>
> ______________________________**_________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>
http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>
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You can use CallInst::hasFnAttr().  It checks for attributes in the 
instruction and in the function decl.

http://llvm.org/docs/doxygen/html/Instructions_8cpp_source.html#l00345

Nuno

----- Original Message -----
> Hi,
>
> Building the following C code I get a call instruction that has no 
> noreturn
> attribute, while the function itself does have it.
>
> void foo(void **b) {
>  __builtin_longjmp(b, 1);
> }
>
>
> define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable {
> entry:
>  %0 = bitcast i8** %b to i8*
>  tail call void @llvm.eh.sjlj.longjmp(i8* %0)
>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>  unreachable
> }
>
> declare void @llvm.eh.sjlj.longjmp(i8*) noreturn nounwind 
> <<<<<<<<<<<<<<<<<
>
>
> I've hit this in asan where it checks the noreturn attribute in the
call
> instruction, but not in the function object.
> Who is wrong here? Should asan also check noreturn in the called function?
>
> Thanks,
>
> --kcc

On Fri, Nov 30, 2012 at 2:21 AM, Nuno Lopes <nunoplopes at sapo.pt> wrote:
> You can use CallInst::hasFnAttr().  It checks for attributes in the
> instruction and in the function decl.
>
Indeed....
And we have
    bool doesNotReturn() const { return hasFnAttr(Attributes::NoReturn); }
and asan code called CI->doesNotReturn  and it did not work, but now it
works.
Hmm.
Anyway, thanks!

--kcc

>
>
http://llvm.org/docs/doxygen/**html/Instructions_8cpp_source.**html#l00345<http://llvm.org/docs/doxygen/html/Instructions_8cpp_source.html#l00345>
>
> Nuno
>
>
> ----- Original Message -----
>
>> Hi,
>>
>> Building the following C code I get a call instruction that has no
>> noreturn
>> attribute, while the function itself does have it.
>>
>> void foo(void **b) {
>>  __builtin_longjmp(b, 1);
>> }
>>
>>
>> define void @_Z3fooPPv(i8** %b) noreturn nounwind uwtable {
>> entry:
>>  %0 = bitcast i8** %b to i8*
>>  tail call void @llvm.eh.sjlj.longjmp(i8* %0)
>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<**<<<<<<
>>  unreachable
>> }
>>
>> declare void @llvm.eh.sjlj.longjmp(i8*) noreturn nounwind
>> <<<<<<<<<<<<<<<<<
>>
>>
>> I've hit this in asan where it checks the noreturn attribute in the
call
>> instruction, but not in the function object.
>> Who is wrong here? Should asan also check noreturn in the called
function?
>>
>> Thanks,
>>
>> --kcc
>>
>
>
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