llvm dev - Aug 2016 - CFI error with binutils 2.27

Hi,

:If I compile this file with debugging enabled (clang/LLVM TOT)

int main()
{
}

I get the error

Error: inconsistent uses of .cfi_sections

 From the 2.27 binutils assemblers. It seems that 2.27 doesn't like the

.cfi_sections .debug_frame

directive following previous .cfi directives. The assemblers seem to be 
happy if the .cfi_sections directive precedes any other .cfi directive. 
Is this a bug in binutils or LLVM? It looks as if a fix might be to move 
the generation of the .cfi_sections directive from endModule() to 
somewhere else (maybe a non-existant beginModule()?).

Could someone give me some hints about what the right approach might be? 
It looks as if the ARM code generator might need special handling also 
since it appears to emit the .cfi_sections directive itself.

Thanks for any suggestions.

-Rich

On 08/06/2016 11:39 AM, Richard Pennington via llvm-dev
wrote:
> Hi,
>
> :If I compile this file with debugging enabled (clang/LLVM TOT)
>
> int main()
> {
> }
>
> I get the error
>
> Error: inconsistent uses of .cfi_sections
>
> From the 2.27 binutils assemblers. It seems that 2.27 doesn't like the
>
> .cfi_sections .debug_frame
>
> directive following previous .cfi directives. The assemblers seem to 
> be happy if the .cfi_sections directive precedes any other .cfi 
> directive. Is this a bug in binutils or LLVM? It looks as if a fix 
> might be to move the generation of the .cfi_sections directive from 
> endModule() to somewhere else (maybe a non-existant beginModule()?).
>
> Could someone give me some hints about what the right approach might 
> be? It looks as if the ARM code generator might need special handling 
> also since it appears to emit the .cfi_sections directive itself.
>
> Thanks for any suggestions.
>
> -Rich
As a work-around I modified DwarfCFIException.cpp and ARMException.cpp 
to send the .cfi_sections directive before the first function is 
processed. Seems to work.

-Rich

Was there any determination as to whether this is an LLVM bug or a Binutils bug?

I am using Binutils v2.26 plus some subsequent custom mods, and hoping to update
to v2.27 soon so that I can ditch the mods and it would be good to know what I
should expect.

Thanks,

	MartinO

-----Original Message-----
From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Richard
Pennington via llvm-dev
Sent: 06 August 2016 17:40
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] CFI error with binutils 2.27

Hi,

:If I compile this file with debugging enabled (clang/LLVM TOT)

int main()
{
}

I get the error

Error: inconsistent uses of .cfi_sections

 From the 2.27 binutils assemblers. It seems that 2.27 doesn't like the

.cfi_sections .debug_frame

directive following previous .cfi directives. The assemblers seem to be happy if
the .cfi_sections directive precedes any other .cfi directive.
Is this a bug in binutils or LLVM? It looks as if a fix might be to move the
generation of the .cfi_sections directive from endModule() to somewhere else
(maybe a non-existant beginModule()?).

Could someone give me some hints about what the right approach might be? 
It looks as if the ARM code generator might need special handling also since it
appears to emit the .cfi_sections directive itself.

Thanks for any suggestions.

-Rich



_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Without any other feedback I went under the assumption that it was an 
LLVM error. The patch I made was pretty trivial and I'm happily using 
2.27, but I'm waiting to see where people think the real bug is.

-Rich

On 08/09/2016 04:07 PM, Martin J. O'Riordan via llvm-dev
wrote:
> Was there any determination as to whether this is an LLVM bug or a Binutils
bug?
>
> I am using Binutils v2.26 plus some subsequent custom mods, and hoping to
update to v2.27 soon so that I can ditch the mods and it would be good to know
what I should expect.
>
> Thanks,
>
> 	MartinO
>
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
Richard Pennington via llvm-dev
> Sent: 06 August 2016 17:40
> To: llvm-dev at lists.llvm.org
> Subject: [llvm-dev] CFI error with binutils 2.27
>
> Hi,
>
> :If I compile this file with debugging enabled (clang/LLVM TOT)
>
> int main()
> {
> }
>
> I get the error
>
> Error: inconsistent uses of .cfi_sections
>
>   From the 2.27 binutils assemblers. It seems that 2.27 doesn't like
the
>
> .cfi_sections .debug_frame
>
> directive following previous .cfi directives. The assemblers seem to be
happy if the .cfi_sections directive precedes any other .cfi directive.
> Is this a bug in binutils or LLVM? It looks as if a fix might be to move
the generation of the .cfi_sections directive from endModule() to somewhere else
(maybe a non-existant beginModule()?).
>
> Could someone give me some hints about what the right approach might be?
> It looks as if the ARM code generator might need special handling also
since it appears to emit the .cfi_sections directive itself.
>
> Thanks for any suggestions.
>
> -Rich
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

On Sat, Aug 6, 2016 at 7:39 PM, Richard Pennington via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> :If I compile this file with debugging enabled (clang/LLVM TOT)
>
> int main()
> {
> }
>
> I get the error
>
> Error: inconsistent uses of .cfi_sections
>
> From the 2.27 binutils assemblers. It seems that 2.27 doesn't like the
>
> .cfi_sections .debug_frame
>
> directive following previous .cfi directives. The assemblers seem to be
> happy if the .cfi_sections directive precedes any other .cfi directive. Is
> this a bug in binutils or LLVM? It looks as if a fix might be to move the
> generation of the .cfi_sections directive from endModule() to somewhere
else
> (maybe a non-existant beginModule()?).
>
> Could someone give me some hints about what the right approach might be? It
> looks as if the ARM code generator might need special handling also since
it
> appears to emit the .cfi_sections directive itself.
It doesn't seem like a GAS problem to me since they are adhering to
their documentation
(https://sourceware.org/binutils/docs/as/CFI-directives.html) that
says that all .cfi_sections directives
must precede the first .cfi_startproc directive. The check for this
rule was introduced to GAS in commit
bd5608dcc6a76876db06b1af1852252a4282aa2f on Feb 11 2016 (binutils
2.26+) and LLVM doesn't
work for me when using any version of binutils that contains this commit.

I went ahead and filed a bug for this with the LLVM bugzilla, it can be found at
https://llvm.org/bugs/show_bug.cgi?id=29017.
>
> Thanks for any suggestions.
>
> -Rich
>
Thanks,
Artemiy