[LLVMdev] debugging LLVM generated executables???

Mark Oskin oskin at cs.washington.edu
Wed May 7 11:09:10 PDT 2008


Just re-sending this.  Anyone have any suggestions on how to proceed  
with debugging LLVM produced executables?  The problem appears to be  
register-allocated variables.  Global variables and syntax lines do  
get symbols using the llc / as method I described below.  -Mark

On May 6, 2008, at 7:36 AM, Mark Oskin wrote:

>
>> I think you probably need to pass -O0 to llvm-ld.  The link-time
>> optimizations are probably killing your debug info.
>>
> No dice.  Doing it this way makes gdb spew out this:
>
> warning: Could not find object file "/var/folders/cQ/cQ+L3+RP2RWOpE
> +8ZNQdPU+++TI/-Tmp-//ccVljWhn.o" - no debug information available for
> "defs.h"
>
> And then no debug symbols are available.
>
> I also discovered a major down side to the "solution" I found last
> night.  While the line number data does get successfully transfered
> into gdb, I cannot inspect any variables.  Those appear to have been
> lost.
>
> Any other suggestions out there?
>
> thanks!
>
> -mark
>
>> --Owen
>>
>> On May 5, 2008, at 8:21 PM, Mark Oskin wrote:
>>
>>> Hi everyone again,
>>>
>>> I did discover the following works (see below).  However, does  
>>> anyone
>>> know of the "proper" way with LLVM?
>>>
>>> llvm-gcc -g -c -emit-llvm helloworld.c
>>> opt -load=mypass.dylib -mypass < helloworld.o > helloworld-mypass.o
>>> llc -fast -f -o helloworld.s helloworld-mypass.o
>>> as -o helloworld-prime.o
>>> gcc -o helloworld helloworld-prime.o
>>> gdb helloworld
>>>
>>> On May 5, 2008, at 4:17 PM, Mark Oskin wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> I have a question that seems simple, but has been confounding me  
>>>> for
>>>> several hours.  I'd like to debug a binary produced with LLVM.  For
>>>> the life of me, I can't get any symbols into gdb and llvm-db won't
>>>> even start the program nor load any useful information about it.
>>>> Here's my current strategy (which isn't working):
>>>>
>>>> llvm-gcc -g -O0 -c -emit-llvm helloworld.c
>>>> opt -load=mypass.dylib -mypass < helloworld.o > helloworld-mypass.o
>>>> llvm-ld -native -o helloworld helloworld-mypass.o
>>>> gdb helloworld
>>>>
>>>> I've tried several variations on the above.
>>>>
>>>> Any suggestions?
>>>>
>>>> Note, what is critical about the whole thing is I must run
>>>> "mypass" on
>>>> the bytecode file.  I'm hoping there's an easy fix, that will both
>>>> allow me to run my arbitrary pass, and debug a program.
>>>>
>>>> thanks,
>>>>
>>>> -Mark
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