re: About the debugging of gfortran arrays

[Wu Zhou <woodzltc at cn dot ibm dot 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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