[LLVMdev] problems with dwarf/gdb

[Devang Patel]

On Apr 13, 2009, at 11:00 PM, Ken McMillan <kenmcmil at yahoo.com> wrote:

>
> I'm having trouble debugging x86 code generated by LLVM.
> GDB does work with the code, but not correctly, for example,
> the "next" command does not skip over a function call.


This is a known limitation on debug info generated by llvm, at least  
as per Darwin Gdb.

-
Devang
>
> Here's an example.
>
> Source program gdb1.c:
>
> int x;
>
> void foo(){
>  x++;
> }
>
> void bar(){
>  x--;
> }
>
> int main(){
>  foo();
>  bar();
>  return 0;
> }
>
> commands:
>
> $ llvm-gcc -g -emit-llvm  -c gdb1.c -o gdb1.bc
> $ llc gdb1.bc
> $ gcc -m32 gdb1.s -o gdb1
> $ gdb ./gdb1
> GNU gdb Red Hat Linux (6.6-16.fc7rh)
> Copyright (C) 2006 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and  
> you are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for  
> details.
> This GDB was configured as "x86_64-redhat-linux-gnu"...
> Using host libthread_db library "/lib64/libthread_db.so.1".
> (gdb) b main
> Breakpoint 1 at 0x80483a0: file
> /home/mcmillan/projects/impact2/test//gdb1.c, line 11.
> (gdb) run
> Starting program: /home/mcmillan/projects/impact2/test/gdb1
>
> Breakpoint 1, main () at /home/mcmillan/projects/impact2/test// 
> gdb1.c:11
> 11    int main(){
> (gdb) next
> main () at /home/mcmillan/projects/impact2/test//gdb1.c:12
> 12      foo();
> (gdb)
> foo () at /home/mcmillan/projects/impact2/test//gdb1.c:4
> 4      x++;
> (gdb)
> 5    }
> (gdb)
> main () at /home/mcmillan/projects/impact2/test//gdb1.c:13
> 13      bar();
> (gdb)
> bar () at /home/mcmillan/projects/impact2/test//gdb1.c:8
> 8      x--;
> (gdb)
> 9    }
> (gdb)
>
> Notice the "next" causes gdb to step into "foo" instead of stepping
> over it.
>
> Also, notice that I used -m32 on the gcc command line to assemble
> the LLVM-generated source file. This seems to be needed, though
> I don't know why LLVM would be generating 32-bit code on my
> 64-bit machine.
>
> Versions: LLVM 2.5 (though got same result with 2.2), gcc 4.1.2,
> gdb 6.6, running on x86 Linux (Fedora 7).
>
> Has anyone had similar issues with gdb? Is debugging with gdb
> known to work properly on other platforms?
>
> Thanks for any help --
>
> Ken McMillan
>
>
>
>
> -- 
> View this message in context: http://www.nabble.com/problems-with-dwarf-gdb-tp23033690p23033690.html
> Sent from the LLVM - Dev mailing list archive at Nabble.com.
>
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