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re: About the debugging of gfortran arrays
- From: Wu Zhou <woodzltc at cn dot ibm dot com>
- To: Feng Wang <wf_cs at yahoo dot com>
- Cc: fortran at gcc dot gnu dot org, gdb at sources dot redhat dot com
- Date: Wed, 29 Jun 2005 19:07:09 +0800 (CST)
- Subject: re: About the debugging of gfortran arrays
- References: <20050630032305.44227.qmail@web15603.mail.cnb.yahoo.com>
Hi Feng,
Thanks for your reply. I had opened a bug:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22244
and added you into the CC-list. Thanks for looking into this.
Cheers
- Wu Zhou
On Thu, 30 Jun 2005, Feng Wang wrote:
> --- Wu Zhou <woodzltc@cn.ibm.com>写道:
>
> > Hello all,
> >
> > I am trying to use gdb to debug gfortran program and encountered some
> > problems with arrays:
> >
> > 1. The first one is about the lower bound. It seems that gfortran change
> > the lower bound of some arrays to 0 by default (I got this feeling from my
> > experience and I also see this kind of transfer in part of the code in
> > gcc/fortran/trans-type.c. Dunno know whether it apply to all arrays.
> > Anyone could confirm or deny this? Thanks in advance!)
>
> Yes, all array.
>
> >
> > To handle this, GDB need to make responsive change. But I have one
> > question here: is this kind of design (change the lower bound of array to
> > zero) indispensible here? Is it ok to still output the original bounds in
> > the
> > debug info?
>
> IMHO, one dimension array is easy to be changed. But multi-dimension array is
> not supported under this structure.
>
> >
> > 2. The second one is about two-dimension array. In the debuginfo output
> > by gfortran, two-dimension array will be flatten to one-dimension. Take a
> > look at the following testcase please:
> >
> [snip]
> >
> > Although there is no problem for the output binary, but it make some
> > trouble for GDB. So I am thinking of whether there is any solution
> > for this in gfortran's side?
> >
> > For example, treat it as one-dimension array in the outputed binary, but
> > still output two-dimension one in the debug information. Maybe others?
> >
> Ok. I think we can build nested array type like C FE and reserve other type
> discriptors. But from the explanation in trans-type.c it seems hard to solve
> some other problems. This should be comfirmed by maintainers. Paul B, Steven B,
> give some comments?
>
> It's not only gdb problem, but also affects performance and optimization on the
> tree-level. We lose the dimension infomation and can not get correct data
> dependency. This limits many optimizations like loop interchange and loop
> distribution, etc.
>
> I think you can file a bug report. See:
> http://gcc.gnu.org/bugzilla
>
>
> Best Regards,
> Feng Wang
>
> --
> Creative Compiler Research Group,
> National University of Defense Technology, China.
>
>
>
>
>
>
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