[llvm-dev] Help in generating Debug symbols

[Robinson, Paul via llvm-dev]

> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
> Nagaraju Mekala via llvm-dev
> Sent: Friday, December 08, 2017 10:06 AM
> To: Florian Hahn
> Cc: llvm-dev at lists.llvm.org; nd
> Subject: Re: [llvm-dev] Help in generating Debug symbols
> 
> Hi Florian,
> 
>    Thanks for the reply.
> 
> On Fri, Dec 8, 2017 at 6:48 PM, Florian Hahn <florian.hahn at arm.com> wrote:
> > Hi,
> >
> > On 08/12/2017 06:24, Nagaraju Mekala via llvm-dev wrote:
> >>
> >> Hi all,
> >>
> >>    I am new to LLVM. Currently working on adding an embedded target to
> >> LLVM backend.
> >>    I was able to generate the object file for our target using LLVM and
> >> Clang framework.
> >>    The generated object file doesn't contain any debug symbols in it.
> >>
> >
> > What commands are you using?
> llvm/bin/clang -g -target xmb -c a.c
> 
> > Do you get object files with debug info for> other backends?
> Yes, for ARM and X86 targets debug symbols are generating fine.
> 
> > If you pass `clang -g`, debug info should be generated. In> the IR, you
> should have !dbg metadata.
> Yes I can see the !dbg metadata in ll file:

That is not surprising, if all you have done is add a new target.

If you use `clang -g -S` to get an asm file, do you see the
.debug_info and other .debug_* sections?  Do you see .loc directives?
If not, the problem is somewhere in how your target interacts with
CodeGen.  If you see these things in the assembler source, but
assembling to an object file loses the information, then there is
likely some problem with how your target interacts with the MC
layer.  Or, if you are not emitting ELF or MachO object files, but
have your own object format, then you might have a problem with how 
you have implemented the object file stuff.

I hope this helps narrow down the problem for you.
--paulr

> 
> a.c
> ---------------------------
> int main()
> {
>   printf ("Hello World\n");
>  return 0;
> }
> 
> a.ll
> --------------------------------
> @.str = private unnamed_addr constant [13 x i8] c"Hello World\0A\00",
> align 1
> 
> ; Function Attrs: nounwind
> define i32 @main() #0 !dbg !4 {
> entry:
>   %retval = alloca i32, align 4
>   store i32 0, i32* %retval, align 4
>   %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([13
> x i8], [13 x i8]* @.str, i32 0, i32 0)), !dbg !12
>   ret i32 0, !dbg !13
> }
> 
> Thanks,
> Nagaraju
> .
> > Cheers,
> > Florian
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